building control guidance new dwellings & garages - Forest of Dean ...

BUILDING CONTROL 

GUIDANCE 

FOR 

NEW DWELLINGS 

& GARAGES 

Dwellings upto 2 storeys with 

additional guidance for 3 storeys 

OCTOBER 2010: EDITION 5

Introduction 

This document intends to provide education and guidance on how some of the technical 

design and construction requirements of the Building Regulations 2010 can be achieved 

and met for new dwellings up to two storeys in height and within 4.5m of ground level 

and additional guidance is given for three storeys in height which has a floor 4.5m above 

ground level. 

In all cases the design and construction of the proposed works is the responsibility of the 

designer, applicant and contractor and should be carried out to the relevant submitted 

and approved design. For further information reference should be made to the relevant 

Approved Document or standard as well as consulting a suitably qualified and 

experienced construction professional. 

The Approved Documents, which are listed below are available to view on the 

Communities and Local Government web site: www.communities.gov.uk or to purchase 

from The Stationary Office (TSO) on line at www.tsoshop.co.uk or telephone: 0870 600 

5522. 

However, the Building Regulation requirements may be satisfied in other ways or nonstandard 

ways by calculations or test details from a manufacturer or an approved 3rd 

party method of certification such as BBA (British Board of Agreement) Certificate. 

This document can be made available on a range of other formats if required. For further 

information please contact us on 01594 810000. 

Approved Documents and sections they cover; 

A: Structure (2004 edition) including TRADA span tables for solid timber members in 

floors, ceilings and roofs for dwellings (2nd edition 2008)*; 

B1: Fire safety in dwelling houses (2006 edition); 

C: Site preparation and resistance to contaminants & moisture (2004 edition); 

D: Toxic substances (1992 with 2002 amendments); 

E: Resistance to the passage of sound (2003 with 2004 amendments); 

F: Ventilation (2010 edition); 

G: Sanitation, hot water safety and water efficiency (2010 edition); 

H: Drainage and waste disposal (2002 edition); 

J: Combustion appliances & fuel storage systems (2010 edition); 

K: Protection from falling, collision and impact (1998 with 2002 amendments); 

L1A: Conservation of fuel and power in new dwellings (2010 edition); 

M: Access and use of buildings (for disabled, 2004 edition) 

N: Glazing – Safety in relation to impact, opening & cleaning (1998 with 2000 

amendments); 

P: Electrical safety (2006 edition); 

Regulation 7 Materials and workmanship (1992 with 2000 amendments). 

Other guidance documents available: New extensions/garages, Loft 

Conversions, Commercial/industrial buildings & Fire Safety for Conversion of buildings 

into Holiday Lets, Guest Houses & Supervised Groups with Learning Difficulties. 

Important note: Typical section details have been provided in these guidance notes 

for the more common construction methods used in dwellings. These details are 

suggested methods of construction and are for guidance only. You are advised to contact 

a suitably qualified and experienced property professional for details and specifications 

for the most suitable form and method of construction for your project. 

2

CONTENTS PAGE NUMBER 

INTRODUCTION 2 

1.0 ENGAGING A PROPERTY PROFESSIONAL 7 

2.0 OBTAINING BUILDING REGULATIONS APPROVAL 

3.0 EXEMPT BUILDINGS & WORK 8 

4.0 COMPETENT PERSON SCHEME 

5.0 PLANNING PERMISSION, LISTED BUILDING & CONSERVATION AREA CONSENTS 

6.0 THE PARTY WALL ACT 1996 9 

7.0 CONSTRUCTION (DESIGN MANAGEMENT) REGULATIONS AND HEALTH & 

SAFETY AT WORK ACT 

8.0 GENERAL TECHNICAL & PRACTICAL GUIDANCE FOR PROJECTS 10 

PREPARATION, PROTECTION, ACCESS AND DEMOLITION 

PART A: STRUCTURE 11 

A1: SUB STRUCTURE 

Foundations (including basements) 

Diagram 1: Elevation of stepped foundation 

Ground bearing solid concrete floors 12 

Diagram 2: Typical section through a ground bearing solid concrete floor & foundation 

Suspended beam & block ground floor 

Diagram 3: Typical section through a suspended beam & block ground floor 13 

Suspended timber ground floor 

Diagram 4: Typical section through a suspended timber ground floor 14 

Table 1: Ground floor & suspended ground floor insulation requirements 

Garage concrete floor 15 

Diagram 5: Typical section through a garage floor & foundation 

A2: SUPERSTRUCTURE 16 

Cavity walls 

Table 2: Insulation requirements for external cavity walls 

Semi Exposed Walls 

Table 2.1: Insulation requirements to semi exposed walls 

External timber framed walls with separate brick or block finish 17 

External timber framed walls with render finish 18 

Diagram 6: Typical section through external timber framed walls with render finish 

External timber framed walls with cladding finish 17 

Diagram 7: Typical section through external timber framed walls with cladding finish 19 

Detached garage with SINGLE SKIN external walls 

Diagram 8: Design criteria for small detached single storey garages or similar 20 

Plan view of garage 

Wall abutments 21 

Lintels & weep holes 

Structural columns/beams etc 

Expansion joints 

Strapping and restraint 

Cavity Closers 

A3: SEPARATING WALLS & FLOORS 

Masonry party walls separating dwellings 

Timber frame party walls separating buildings 22 

Upgrading sound insulation of existing separating walls 

Party floors separating buildings 

Sound testing requirements 

A4: ADDITIONAL PROVISIONS FOR 3 STOREY BUILDINGS 

Compressive strength of masonry units 

A5: INTERNAL PARTITIONS 23 

Internal load bearing masonry partitions 

Internal load bearing timber stud partitions 

Internal masonry non-load bearing partitions 

3

Internal timber studwork non-load bearing partitions 

A6: INTERMEDIATE UPPER FLOORS 24 

Table 3: Spans for Common Domestic Floor Joist Sizes 

Table 4: Spans for Common Trimmer Joist supporting Trimmed Joists 

Table 5: Spans for Common Trimming Joist supporting Trimmer Joist 

Sound insulation to floors within the dwelling 25 

SVP pipe boxing 

Exposed intermediate upper floors 

Diagram 9: Typical section through an upper floor 

Table 6: Insulation requirements to exposed intermediate floors 

A7: PITCHED ROOFS 26 

Pitched roof coverings 

Pitched roof structure 

Roof trusses (including attic & girder trusses) 

Cut roof construction 

Diagram 10: Typical section through a pitched roof 27 

Table 7: Spans for Common Domestic Timber Rafter Sizes at 400mm spacing 

Table 8: Spans for Common Domestic Timber Ceiling Joist Sizes at 400mm spacing 29 

Table 9: Spans for Common Domestic Timber Purlin Sizes 

Table 10: Permissible Clear Spans for Common Ceiling Binders Sizes 

Roof restraint 

Roof insulation 

Table 11: Insulation laid horizontally between and over ceiling joists 

Table 12: Insulation fixed between/under rafters 29 

Table 13: Insulation fixed between/over rafters 

Diagram 11: Typical roof valley detail 

Diagram 12: Typical section through a dormer roof 30 

Ventilation to pitched roofs 

A8: FLAT ROOF CONSTRUCTION 31 

Table 14: Spans for Common Flat Roof Joist Sizes 32 

Table 15: Insulation Fixed Between/Under Flat Roof Joists 

Table 16: Insulation Fixed above Flat Roof Joists 

Diagram 13: Typical section through a flat (cold) roof 33 

Valleys and lead work 

Lofts hatches, doors & Light wells to roof spaces 

PART B: FIRE SAFETY & MEANS OF ESCAPE 34 

Smoke /heat alarms 

Means of escape windows 

Fire doors & frames 

Means of escape from basements 

Permitted building openings in relation to a boundary: 

Openings within 1.0m of a boundary & openings more than 1.0m from a boundary 

Table 17: Permitted unprotected areas in relation to a relevant boundary 

Fire resistance to elements of structure etc 35 

Table 18: Fire resistance to common elements of structure etc 

Surface spread of flame: wall & ceiling linings 

Table 19: Surface spread of flame: Classification of wall & ceiling linings 

Additional fire safety & means of escape provisions for new 3 storey dwellings 36 

Residential sprinkler systems for means of escape 

PART C: SITE PREPARATION AND RESISTANCE TO CONTAMINANTS & MOISTURE 37 

Horizontal damp proof courses & trays (dpc’s) 

Vertical damp proof courses & trays etc (dpc’s) 

Radon gas protection in sub structures 

3 alternative methods for full radon gas protection in sub structures 

Methane & other gas protection in sub structures 

Tanking systems & Flood risk 38 

4

PART D: CAVITY WALL FILLING WITH INSULATION BY SPECIALISTS 

PART E: RESISTANCE TO THE PASSAGE OF SOUND 39 

PERFORMANCE STANDARDS 

Party walls and floors separating new dwelling/flats. 

Party walls and floors separating conversion of buildings into new dwellings/flats 

Exemptions/ relaxations for conversion of historic buildings into dwellings/flats 

PRE COMPLETION SOUND TESTING 

Testing rate requirements 

Remedial works and re-testing 

NEW INTERNAL WALLS & FLOORS 

PART F: VENTILATION 40 

Ventilation systems 

Purge (natural) ventilation 

Mechanical extract ventilation 41 

Background ventilation 

Background ventilation: Table A & Table B 42 

PART G: SANITATION, HOT WATER SAFETY AND WATER EFFICIENCY 43 

PART H: DRAINAGE AND WASTE DISPOSAL 44 

H1: FOUL WATER DRAINAGE 

New foul water connections to the public sewer 

Foul, rain & storm water drainage systems 

Waste pipes 

H2: SEPTIC TANKS, SEWAGE TREATMENT SYSTEMS & CESSPOOLS 45 

Existing septic tank & effluent drainage 

Non mains foul drainage waste water treatment systems 

Septic tanks 

Sewage treatment systems 46 

Treatment of sewage from septic tanks & sewage treatment systems 

Drainage fields 

Drainage mounds 

Wetlands / reed beds 47 

Percolation test method to calculate area of drainage field. 

Diagram 14: Typical section through a septic tank/sewage treatment system 

drainage field 48 

Diagram 14.1: Typical drainage field layout 

H3: RAINWATER DRAINAGE AND HARVESTING 49 

Rainwater gutters and down pipes 

Table 20: Gutter sizes & pipe outlet sizes for drainage of roof areas 

Rainwater/ grey water harvesting storage tanks & systems 

Surface water drainage around the building 

Oil/fuel separators 50 

H4: BUILDING OVER OR CLOSE TO PUBLIC SEWERS 

H5: SEPARATE SYSTEMS OF DRAINAGE 

H6: SOLID WASTE STORAGE 

PART J: COMBUSTION APPLIANCES & FUEL STORAGE SYSTEMS 51 

SPACE & HOT WATER HEAT PRODUCING APPLIANCES IN GENERAL 

SOLID FUEL APPLIANCES UP TO 50KW RATED OUTPUT 

Construction of open fire place with recess & hearth 

Free standing stove with hearth 

Air supply (ventilation) to solid fuel appliances 

Table 21: Air supply (ventilation) to solid fuel appliances 52 

Carbon monoxide alarms 

Table 22: Sizes of flues in chimneys 

Construction of masonry chimneys 53 

Construction of factory made flue block chimneys 

Construction of factory made metal chimneys 

5

Configuration of flues serving open flue appliances 

Inspection & cleaning openings in flues 

Interaction of mechanical extract vents & opened flue solid fuel appliances 

Chimney heights 54 

Repair/relining of existing flues 

Notice plates for hearths & flues 

APPLIANCES OTHER THAN SOLID FUEL 

Interaction of mechanical extract vents & opened flue combustion appliances 

Gas appliances 

Oil appliances 

Gas heating appliances up to 70kw 

Oil heating appliances up to 45kW 55 

Renewable energy Installations 

Provision of information- commissioning certificates (testing) 

FUEL STORAGE TANKS 

LPG tanks and cylinders up to 1.1 tonnes 

Oil tanks up to 3500 litres 

PART K: PROTECTION FROM FALLING, COLLISION AND IMPACT 56 

Internal stairs, landings and changes in level of 600mm or more 

Diagram 15: Measuring rise & goings 

Diagram 16: Typical internal stair case & guarding construction details 57 

External stairs, landings and changes in level of 600mm or more 

Guarding to upper storey window openings/other openings within 

800mm of floor level 

PART L: CONSERVATION OF FUEL AND POWER IN NEW DWELLINGS 58 

TARGET & DWELLING EMISSIONS RATES 

SAP RATING & ENERGY PERFORMANCE CERTIFICATE 

Fabric standards (worst acceptable standards) 

Recommended starting u values 

U values for party walls 

ENERGY EFFICIENT LIGHTING 59 

LIMITING THE EFFECTS OF SOLAR HEAT GAINS IN SUMMER 

LIMITING THERMAL BRIDGING AROUND EXTERNAL OPENINGS 

AIR PERMEABILITY & PRESSURE TESTING 

Limiting air leakage 

Pressure testing of new dwellings 60 

Alternative to pressure testing 

PROVIDING INFORMATION 

PART M: ACCESS TO AND USE OF BUILDINGS FOR DISABLED 61 

External ramped & stepped approach 

Accessible level door thresholds into the building 

External door opening widths 

Internal passageways/corridors widths & table 

Internal stairs 62 

Accessible switches, sockets, controls etc 

Provision of a ground floor W/C 

PART N: SAFETY GLAZING, OPENING & CLEANING 63 

Safety glass and glazing 

Diagram 17: Glazing in windows, partitions, doors, side panels/screens & walls 

PART P: ELECTRICAL SAFETY 64 

Electrical Installations 

EXTERNAL WORKS- PATHS, DRIVES, PATIO & GARDENS 65 

MATERIALS AND WORKMANSHIP 66 

ADDITIONAL BUILDING CONTROL SERVICES WE CAN PROVIDE 

GLOUCESTERSHIRE BUILDING CONTROL DEPARTMENTS CONTACT DETAILS 67 

USEFUL NUMBERS OF OTHER AGENCIES OR COMPANIES 

6

1.0 Engaging a property professional 

New dwellings are normally complex projects and unless you are experienced in 

construction you will need to get some professional advice/help from the following: 

1. Appointing a suitably qualified and experienced property professional who will prepare 

drawings and designs for your proposal, obtain the necessary approvals and if required 

they will also help you to find a suitable builder and manage the project for you. 

2. Appointing a specialist company who can offer a one stop shop for new dwellings, 

they can prepare drawings and designs for your proposal, obtain the necessary 

approvals and carry out all the necessary construction works to complete the project. 

3. Using an experienced builder. 

2.0 Obtaining Building Regulations approval 

The building owner or agent must make a building regulations application & pay a fee for 

the construction of a new dwelling. All work must comply with the 2010 Building 

Regulations and the technical design and constructional requirements of the current 

Approved Documents A to P and Regulation - 7 Materials and Workmanship. 

The person carrying out the building works is to liaise with and meet the requirements of 

the LA Building Control/Certifying Body, giving required notices of stages of works as 

required by the Building Regulations including: 

Foundation excavations before any concrete is laid 

Over site covering to ground floors before any concrete is laid 

Foul & surface water drainage before any pipes are covered over 

Structural timbers (upper storey floor joists/beams and roof structure before any 

coverings are fixed 

Completion of building-prior to occupation 

There are two methods of making a Building Regulations application as follows: 

2.1 Full Plans application 

This is often thought of as the traditional way of applying for Building Regulations 

Approval. The building designer will draw up detailed plans and supporting information 

for the proposed scheme and will send them to us together with a completed application 

form and the necessary fee which are available to down load from our web site at: 

www.fdean.gov.uk. We will then check the details and following any necessary 

consultations and liaisons with the building designer a Building Regulations Approval will 

be issued. 

Work can start any time after the application has been received although it is wise to wait 

until the scheme has had its initial check under the Building Regulations, this usually 

takes between two and three weeks. 

Our team of surveyors will liaise with your builder and inspect the work as it progresses 

on site. When the project is satisfactorily completed a Building Regulations Completion 

Certificate will be issued showing that the project has been independently inspected and 

that it complied with the Building Regulations. 

2.2 Building Notice application 

This system is best suited to minor domestic work carried out by a competent builder. 

Under this scheme no formal Approval of plans is issued and work is approved on site as 

it progresses. To use the Building Notice process you or your agent will need to submit a 

completed Building Notice application form together with a site location plan, the 

required fee, energy assessment and water efficiency calculation. The application forms 

are available to down load from our web site at: www.fdean.gov.uk. 

7

Work can commence 48 hours after the notice has been received. 

When work commences one of our surveyors will meet with your builder to discuss your 

intentions, to agree how the work should be carried out, agree when the work will need to 

be inspected and to establish whether any further information will be required e.g. 

structural calculations or drawings. 

When the project is satisfactorily completed a Building Regulations Completion 

Certificate will be issued showing that the project has been independently inspected and 

that it complied with the Building Regulations. 

3.0 Exempt buildings and work 

Green Houses & agricultural buildings: Buildings used for agriculture or keeping of 

animals providing no part is used as a dwelling and is more than 1.5 times its height from 

a building containing sleeping accommodation 

Temporary buildings: Buildings erected for less than 28 days 

Ancillary buildings: Buildings used in connection with the sale of buildings or plots on 

that site, or in connection with a building project or mine/quarry and contains no sleeping 

accommodation. 

Small detached buildings (garages, workshops or sheds): A detached single storey 

building with less than 30m 2 internal floor area, with no sleeping accommodation. If 

constructed substantially of combustible materials it must be positioned at least one 

metre from the boundary of its cartilage. Other detached buildings with less than 15m 2 

internal floor area, with no sleeping accommodation. (no boundary restrictions if 

constructed of combustible materials) 

Conservatory, porch, covered yard/way & carports: A detached single storey building 

with less than 30m 2 internal floor area, fitted with safety glass in critical locations in 

compliance with ADN. Existing walls, doors & windows of the building separating the 

conservatory or porch is to be retained or, if removed are replaced with elements that 

meet the energy efficiency requirements of ADL1B. The heating system of the dwelling 

must not be extended into the conservatory or porch. Carports must be open on two 

sides. 

4.0 Competent Person Scheme 

Certain works can be carried out by an installer who is registered with a Competent 

Persons Scheme and will not require building regulations approval. Further details of the 

works covered by a competent persons scheme can be found at: 

www.communities.gov.uk 

5.0 Planning Permission, listed building & conservation area consents 

Planning permission, listed building/conservation area consents may be required for your 

proposed development and no works should be commenced until approval has been 

given by the planning department. 

If the requirements of the building regulations will unacceptably alter the character or 

appearance of a historic/listed building/ancient monument or building within 

a conservation area, then the requirements may be exempt or improved to what is 

reasonably practical or acceptable and would not increase the risk of deterioration of the 

building fabric or fittings in consultation with the local planning authorities conservation 

officer. For any further information, please contact the FODDC duty planning officer on 

01594 810000. 

8

6.0 The Party Wall Act 1996 

If the project affects a party wall, you may be required to give your neighbor the 

required notice under the Party Wall Act. 

Two months notice in writing is to be given to adjoining owner(s) for the following works 

to an existing Party Wall: 

Support of beam 

Insert DPC through wall 

Raise wall or cut off projections 

Demolition and rebuilding 

Underpinning 

Insert lead flashings 

Excavations within 3 meters of an existing structure where the new foundations 

will go deeper than adjoining foundations, or within 6 meters of an existing 

structure where the new foundations are within a 45 degree line of the adjoining 

foundations. 

In the event of a disagreement, a Party Wall Surveyor may be required to resolve the 

dispute under the terms of the Party Wall Act. Copies of the Party Wall Act can be 

obtained from the Council Offices or www.communities.gov.uk 

7.0 Construction (Design and Management) Regulations 2007 (CDM) 

The Construction (Design and Management) Regulations 2007 apply to every 

construction project. If you are about to undertake construction work, which could include 

alterations, extensions, routine maintenance, new build or demolitions, then you need to 

know to what extent these Regulations will apply to you and whether you are a duty 

holder under these Regulations. 

With non-domestic* projects expected to last longer than 30 days, or more than 500 man 

hours, you will require the assistance of an advisor called a CDM Co-ordinator, who 

should be appointed at the earliest opportunity, before detailed design work is complete. 

If you are a Client thinking of commissioning work, a Designer appointed to work on a 

project, or a builder/developer about to undertake work, you should be aware of your 

responsibilities or duties under CDM 2007. 

*Non-domestic Clients are people who commission building works related to a 

trade or business, whether for profit or not. This work can be carried out on a 

domestic property; it is the type of Client that matters, not the type of property. 

9

8.0 General technical & practical guidance for projects 

Preparation, protection, access, demolition & ground investigation 

Demolitions, existing structures to be supported & protected where necessary, any 

existing sub structures (e.g. foundations and slab etc), taken up & removed off site to a 

licensed tipping site. Where the demolition of a structure or part of a structure exceeds 

50m3, a notice of the proposed demolition should be sent to the local authorities building 

control department before works commence. Standard format notice is available to down 

load at our web site: www.fdean.gov.uk. 

Provide all necessary health and safety requirements including; site security, scaffolding, 

access ladders, material hoists, temporary protection and working platforms etc which 

are to be erected, maintained, certificated, dismantled and removed by suitably qualified 

and insured specialists. 

All plumbing, drainage, heating, electrical services etc to be carried out by suitably 

qualified & experience specialists or registered competent persons, tested & appropriate 

certification issued where required in this specification. 

Any asbestos/contaminated soil/lead paint is to be inspected & removed by a specialist. 

Asbestos is to be removed and disposed off site by a specialist licensed contractor as 

required under the Control of Asbestos Regulations 2006. 

Ground to be prepared for new works as described including location and 

alteration/modifications to all existing services as necessary, including sealing up, 

capping off, disconnecting, removing redundant services as necessary. 

Prior to and during works, the person carrying out the works is to liaise with and meet the 

requirements of the relevant Service Authorities, including the location and protection of 

all services as necessary. 

External paths, drives, patios, walls, fences & gardens etc, to be taken up and 

relayed/extended as necessary to accommodate the new works as described. 

All structural timber is to be grade C24, stress graded to BS 4978 and sawn to BS 4471. 

All timber is to be protected on site to minimize moisture content which must not exceed 

22%. 

An initial ground investigation assessment should be carried out including a desk study 

and walk over survey which should be recorded and evaluated by a suitably qualified and 

experienced person, and where necessary further basic geotechnical and contamination 

investigations should be carried out by a suitably qualified and experienced person. 

Where the initial assessment and basic investigations identify suspected hazards, further 

detailed investigations and remedial reports are required from a specialist and copy sent 

to building control and approved before works commence on site. 

10

Part A: Structure 

A1: Sub structure 

Foundations (including retaining walls & basements) 

Foundations to be constructed at a minimum depth of 750-1000mm, below the influence 

of drains, and or surrounding trees on level firm natural undisturbed ground of adequate 

ground bearing capacity to the approval of the building control surveyor. 

Strip foundations to be a minimum width of 600mm and thickness of 225mm and trench 

fill foundations should have a minimum width of 450mm and a minimum 500mm 

thickness of concrete. The concrete mix should be ST2 or GEN1. 

Alternative foundation designs, i.e. raft, piles, retaining walls & basement to be designed 

by a suitably qualified person and approved by building control before works commence 

on site. Where applicable, a suitable basement tanking system is to be assessed & 

designed by a tanking specialist suitable for the site conditions & proposed building 

construction to prevent the passage of moisture into the building, which must be 

approved by building control before works commence. Retaining walls require 100mm 

diameter slotted ground water drainage pipe laid around the outside perimeter of any 

retaining wall at 1:60 gradient and taken to a suitable sized soak away system. 

Foundations are to be provided centrally positioned under all exterior, party and interior 

load bearing walls, steps in foundation level should not exceed its thickness and should 

overlap by twice its thickness. Two layers of B503 mesh reinforcement or stronger are to 

be provided, one top and bottom with 75mm cover to the foundations in the Forest of 

Dean mining and Mineral Valuer areas (please contact building control for area details). 

Walls below DPC level up to 1m deep are to be constructed with two skins of 7N/mm² 

100mm or 140mm if over 1m deep concrete blocks 1:3 cement mortar in-filled with 

concrete to a maximum of 225mm below DPC level. Block and cavity width and wall tie 

spacing, etc, to be same as the wall above, but with a row of wall ties to support the 

cavity wall insulation below DPC level. 

Diagram 1: Stepped foundation detail 

Foundations should unite at 

each change in level 

L 

Minimum overlap L = twice height of step, 

or thickness of foundation or 300mm, 

whichever is the greater 

S should not be greater than T 

(for trench fill foundations, minimum overlap 

L = twice height of step or 1metre, 

whichever is the greater) 

S 

T 

11

Ground bearing solid concrete floors (worst case U-value 0.25- suggested U-value 

0.13 W/m².k) 

Topsoil and vegetable matter to be cleared from site and floor to be in filled with minimum 

150mm/maximum 600mm clean sand blinded compacted hardcore. A 300um (1200g) 

continuous polythene DPM/radon barrier is to be lapped & sealed at all joints, laid over 

sand blinded hardcore & linked to DPC’s in walls. Floor & external perimeter edges of 

floor slab to be insulated with floor grade insulation thickness and type in Table below, 

provided under a minimum 100mm thick ST2, or Gen1 concrete floor slab with a trowel 

smooth surface with 25mm up stands to the external walls. A 500g polythene separating 

layer is to be installed between the concrete slab and insulation if using a foil faced 

polyurethane/PIR type insulation board. Insulation to be omitted and concrete thickness 

increased in areas where non-load bearing partitions are built off the floor slab. Where 

area of fill exceeds 600mm the floor is to be suspended as detailed in this guidance. 

Diagram 2: Typical section through a ground bearing solid concrete floor 

& foundation (not to scale) 

Damp proof course 

and insulated closer 

DPC 150mm above 

ground level 

radon dpc tray sealed 

with gas proof tape to 

dpm/radon barrier 

Back fill cavity with 

concrete 

600mm 

All external widows and doors to be double 

glazed (see options in specification) 

100mm minimum width insulation block (see 

options in specification) 

Wall grade insulation (see options in 

specification) 

50mm clear cavity if using partial fill cavity wall 

insulation (see options in specification) 

Stainless steel wall ties and spacings as detailed 

in specification 

100mm minimum width external wall in 

materials to match existing or as specified in 

planning permission 

25mm wide insulation to prevent cold bridging 

65mm thick cement/sand screed 

(optional) 

100mm thick concrete slab 

Floor grade insulation (see options in 


1200g damp proof membrane/radon 

gas barrier 

Sand blinded hardcore mechanically 

compacted in 150mm layers. (floor 

slab to be suspended where depth of 

fill exceeds 600mm deep* 

600 x 200mm concrete strip foundation or trench fill foundation as detailed in 

specification, to be 750-1000mm deep depending on sub soil conditions. Actual depth 

to be agreed on site with building control surveyor. Foundation depths in relation to trees 

to be in accordance with NHBC tables- contact building control for guidance. 

*Note: where full radon protection is require, proprietary radon gas sumps are to be 

installed in sub structure & connected to a proprietary fan assisted duct system in 

compliance with Part C of this guidance. 

Suspended beam & block ground floor (worst case U-value: 0.25-suggested U-value 

0.13 W/m².k) 

Remove top soil & vegetation, apply total weed killer – minimum space below underside 

of floor to be 150mm. PCC beams to be supplied and fixed to beam manufacturers plan 

layout and details. (copies to be sent to Building Control and approved before works 

commence on site). 

Typically for domestic loading and spans pre-stressed beams are 155mm deep X 125mm 

wide and fixed at 520mm ctrs, minimum bearing 100mm onto DPC course and load 

bearing walls. All garage floors to be designed suitable for loadings. 

Clean all beams edges and lay abutting 100mm thick X 225mm wide X 440mm long 

3.5kn conc blocks to BS6073 pt.1, wet and grout all joints with 1:4 cement/sand mix. 

Below non-load bearing parallel partitions provide double beams. 

12

Sub structure void to be vented on opposing sides to provide cross ventilation using 225 

X 150mm proprietary ventilators at 2000mm ctrs, inner ground level to be above external 

ground levels. 

Lay 1200g (300 um) visqueen dpm/radon barrier, with 300mm laps double welted and 

taped at joints and service entry points using Radon gas proof tape, over beam & block 

floor. Lay floor grade insulation over DPM to the thickness and type as indicated in table 

below. Lay 500g separating layer over any foil faced polyurethane type insulation board 

and lay 75mm sand/cement screed over and prepare for floor finishes as required. 

Diagram 3: Typical section through a suspended beam & block ground floor 

(not to scale) 

Damp proof course & insulated 

closer 

Weep holes 

225 x 75mm grilled air bricks 

& proprietary telescopic vents 

through opposing walls at 

2.0m ctrs* 

DPC 150mm min above gl 

Alternative 

1200g DPC basic 

radon barrier over 

complete building foot 

print to comply with 

NHBC requirements 

600mm 

Double glazed windows as detailed in specification 

Cavity wall construction as detailed in specification 

Continuous dpc tray sealed with gas proof tape to dpm 

75mm sand/cement screed 

dpc under beams 

75mm min floor grade insulation as table 1 

1200g dpm/radon barried 

Pcc beam suitable for spans & 

loadings as beam manf details 

100mm dense conc blocks 

75mm concrete blinding layers 

75mm min 

air void 

600 x 750mm (adjusted to foundation depth)concrete trench 

fill foundation as detailed in specification, to be 750-1000mm 

deep depending on sub soil conditions. Actual depth to be 

agreed on site with building control surveyor. Foundation 

depths in relation to trees to be in accordance with NHBC 

tables- contact building control for guidance. 

*Note: for full radon protection a radon fan & flue can be connected to the 

floor vents if required 

Suspended timber ground floor (worst case U-value 0.25- suggested U-value 0.13 

W/m².k) 

Remove top soil & vegetation, apply total weed killer & 150mm min thick sand blinded 

hardcore, lay 100mm min thick un-reinforced concrete oversite (concrete mix should be 

in accordance with BS 8110, BS 5328, mix type ST2 or GEN1), on 1200g DPM which 

should extend across cavity as basic Radon protection and positioned to prevent water 

collection. 

Allow a ventilated air space at least 75mm from the top of the oversite concrete to the 

underside of any wall plates and at least 150mm to the underside of the suspended 

timber floor or insulation. Provide sub floor ventilation using 225 x 75mm grilled air bricks 

& proprietary telescopic vents through two opposing external walls at 2.0m ctrs to vent all 

parts of the floor void. Ducts to be sealed using gas proof tap if they pass through the 

Radon barrier. 

13

Joists to be supported off proprietary heavy duty galvanized joist hangers. Hangers to be 

built into new masonry walls or fixed to treated timber wall plate (same size as joists), 

resin bolted to existing walls at 600mm ctrs using 16mm diam high tensile bolts. Where 

necessary, floor joists can be supported on treated wall plates & dpc onto masonry 

honeycombed sleeper walls onto oversite concrete. 

Floor joists sizes as stated on plans, or table below. Joists to be grade C24 kiln dried 

floor joists fixed at 400mm ctrs (depth to be increased where necessary to match floor 

levels). Proprietary galvanized steel strutting to be fixed at mid span for 2.5 - 4.5m span 

and 2 rows at 1/3rd points for spans over 4.5m. 

Floor to be insulated with floor grade insulation thickness and type in table below, friction 

fixed between joists. Fix 22mm moisture resistant t & g flooring sheets to BS 5669 type II 

or II/III laid with long edge across the joists. All joints to positioned over joists, glued & 

nailed using 55mm X 10g annular ring shank nails. 

Diagram 4: Typical section through a suspended timber ground floor (not to scale) 

Damp proof course & insulated 

closer 

Weep holes 

Dpc tray 

225 x 75mm grilled air bricks 

& proprietary telescopic vents 

through opposing walls at 

2.0m ctrs* 

DPC 150mm min above gl 

1200g DPC 

basic radon barrier 

over complete 

building foot print 

*Note: for full radon protection a radon fan & flue can be connected to the floor vents if 

required 

600mm 

Double glazed windows as specification 

Insulated cavity wall construction as 

Specification 

22mm moisture resistant flooring sheets 

Floor joists as table 4 

Galv hangers built into walls or fixed to wall 

plates resin bolted to walls 

Insulation as table 1 fixed between joists 

& supported on battens fixed to joists 

w/plate on dpc 

honey combe sleeper wall 75mm 

min 

100mm oversite concrete slab 

Blinded hardcore 

150mm 

min 

600 x 750mm (adjusted to foundation depth)concrete trench 

fill foundation as detailed in specification, to be 750-1000mm 

deep depending on sub soil conditions. Actual depth to be 

agreed on site with building control surveyor. Foundation 

depths in relation to trees to be in accordance with NHBC 

tables- contact building control for guidance. 

Table 1: Ground floor & suspended ground floor insulation requirements 

Suggested U-value: 0.13 W/m².k 

Insulation Type Minimum Thickness Required 

Kingspan Kooltherm K3 or 

125mm (floor P/A ratio of 0.5) 

other approved with K value of 0.020 

Alternatives TBA 

14

Garage concrete floor 

Power floated 150 mm thick concrete slab (concrete mix should be in accordance with 

BS 8110, BS 5328, mix type ST2 or GEN1), with 1 layer A252 steel mesh positioned mid 

span of slab on 1200g visqueen dpm/radon barrier on sand blinding on min. 150 well 

consolidated sulphate free clean hardcore.(no reclaimed demolished material is 

permitted). 

1:80 fall on floor from back of garage to front garage door, floor to be thickened to 

300mm at garage entrance. 

Provide 25mm polystyrene compressible clay board to perimeter of walls. 

If hardcore is more than 600mm deep- slab to be reinforced further, to 

NHBC/LA/Engineers requirements. 

100mm thick masonry step down into garage to be provided at doorways. 

Diagram 5: Typical section through a garage floor & foundation (not to scale) 

DPC 

600mm 

Painted render on 100mm dense 

conc block or bricks 

Piers built off fnds & extend full 

height of walls & gables 

600 x 225mm concrete 

strip foundation or 

trench fill foundation as 

detailed in specification, 

750-1000mm deep as 

agreed on site with 

building control surveyor 

150mm thick concrete slab 

1 layer A 252 steel mesh mid span 

1200g damp proof membrane 

Slab thickened at doorway 

Sand blinded hardcore 

mechanically compacted in 

150mm layers. (floor slab to be 

suspended where depth of fill 

exceeds 600mm deep) 

15

A2: Superstructure 

External walls 

Cavity walls (worst case U-value 0.30- suggested U-value 0.18 W/m².k) 

Walls to consist of either approved reconstituted stone facings,100mm tooled flush 

jointed brickwork or 2 coat rendered 100mm dense concrete blockwork external skin 

dependant upon exposure with a 100mm thick lightweight high performance 2.8N/mm² 

insulation block with either a 13mm lightweight plaster finish or 12.5mm plasterboard 

skimmed drylining. Ensure all gaps & all voids are sealed to prevent any air leakage. 

Where required external natural stone facings to be tied to external blockwork with wall 

ties as detailed below and foundation widths increased by 150mm. 

Walls to be built with 1:1:6 cement mortar and tied with BBA approved 275mm long 

Ancon ST1 stainless steel wall ties or other approved double dip type tie in compliance 

with BS 5628 & BS EN 845-1 , built 75mm min into each wall at maximum spacing in 

compliance with wall tie manufacturers details and typically at 600mm max horizontal, 

450mm max vertical and 225mm max at reveals, verges and closings for cavities up to 

125mm wide. For cavity widths of 100mm use 250mm long ties- see table below*. 

Cavity width and insulation details to be constructed as Table 2 below to achieve a ‘U’ 

value of not more than 0.28 W/m².k. Wall insulation to be continuous with roof insulation 

level and taken below floor insulation levels as manufacturer’s details. 

Table 2: Insulation requirements for external cavity walls with 100mm dense 

Brick or rendered block external skin & internal plaster/dry lining plaster finish 

Clear cavity 

Insulation type & Overall cavity Internal Block Type 

width required 

Partial cavity fill 

Minimum thickness width required & Thickness 

50mm 75 mm Kingspan 125mm* 100 mm high 

Kooltherm K8 or 

performance 

Other approved with 

insulation block 


K value of 0.020 

(k value 0.15 or less 

* Cavities can be reduced to 100mm in compliance with insulation manufacturers 

details, subject to any building warranty provider requiring a minimum clear 

cavity of 50mm 

Semi Exposed Walls (worst case U-value 0.30- suggested U-value 0.18 W/m².k) 

Semi exposed walls to unheated rooms such as garages etc, to be constructed and 

insulated as external walls or constructed of 2.8/mm² 100mm solid dense concrete blocks 

with 50 X 125mm deep timber studs or proprietary metal stud partition wall system with 

insulation friction fixed between vertical studs (as detailed in table below), 

finished with 12.5mm vapour checked plaster board (or 500g polythene vapour check) 

Table 2.1: Insulation requirements to semi exposed walls 

Insulation Type Minimum Thickness mm 

Kingspan Kooltherm K12 or other 

120 mm 

approved with a K value of 0.020 


16

External timber framed walls with separate brick or block finish (worst case U-value 

0.30- suggested U-value 0.18 W/m².k) 

Design, manufacture, supply, erection & certification of the complete timber frame 

including roof, walls, lintels & floors etc to be carried out by a specialist timber frame 

manufacturers in compliance with structural engineers details and calculations. Shell of 

building to be air sealed and fitted with protective coverings, and measures to prevent 

condensation and ingress of moisture into the building. All details to be approved by 

building control before works commence on site. Moisture content of timber should not 

exceed 20% and to be kiln dried & grade C24, workmanship to comply to BS 8000:5. All 

timber to be treated using an approved system and all fixings to be stainless steel or other 

approved. 

Timber framed walls to be insulated with 120mm thick Kingspan Kooltherm K12 thermal 

insulation board friction fixed between studs, with12.5mm vapour checked plaster board 

fixed to studs and 3mm skim coat of finishing plaster. All junctions to have water tight 

construction, seal all perimeter joints with tape internally and with silicon sealant 

externally. 

External wall to be approved brick/reconstituted stone/ painted sand & cement render 

(render to BS 5262), on 100mm medium dense external concrete as indicated on plan 

layouts. Masonry walls/mortar/render specifications are contained elsewhere in this 

guidance. 

External masonry skin to be tied to timber frame studs (not the sheathing) using BBA 

approved proprietary flexible stainless steel or other approved wall ties in compliance with 

BS 5628 & BS EN 845-1, at ctrs not exceeding 600mm horizontally and 450mm vertically 

and 225mm max at reveals. Wall ties should be embedded in mortar to a minimum depth 

of 75mm with a slight fall towards the external brickwork. Provide proprietary flexible 

water and fire resistant cavity barriers at eaves level, gable end walls and vertically at 

junctions with separating walls & horizontally at separating walls with continuous dpc tray 

over, installed in compliance with manufacturers details. 

Ensure all gaps & all voids are sealed to prevent any air leakage. 

17

External timber framed walls with render finish (worst case U-value 0.30- suggested 

U-value 0.18 W/m².k) 

Render finish (to BS 5262) applied in 3 coats at least 16mm – 20mm thick overall to 

render lath. First & second coats 1:3 (cement : sand with plasticizer). final coat 1:6 

(cement : sand with plasticizer) proportions by volume. Render should be finished onto 

an approved durable render stop, angle beads or jointing sections- stainless steel or 

other approved using drilled or shot fired fixings only. Stainless steel render lath fixed 

(using stainless steel staples) to vertical studs at 600mm max ctrs. laps wired together at 

150mm ctrs. (Mesh to be backed by a water resistant membrane) & fixed to: 

Treated battens - 25 x 50mm preservative treated battens fixed vertically to studs at max 

600mm ctrs using 75mm long hot dipped galv or stainless steel annular ring nails, fixed 

to: Breathable membrane- ‘Tyvek or similar approved suitable for timber framed walls to 

current BBA certification, fixed to: External quality plywood- 12mm thick marine ply wood 

(or other approved) fixed to: Treated timber frame constructed using: 125/150mm x 

50mm head & sole plates and vertical studs (including 2 rows noggins) at 400mm ctrs, to 

s/engineers details & calculations, with 120mm thick Kingspan Kooltherm K12 thermal 

insulation board friction fixed between studs, with12.5mm vapour checked plaster board 

fixed to internal face of studs and finished with 3mm skim coat of finishing plaster. All 

junctions to have water tight construction, seal all perimeter joints with tape internally and 

with silicon sealant externally. 


Diagram 6: Typical section through external timber framed walls with painted 

render finish (not to scale) 

Masonry paint finish 

16-20mm thick render finish 

Stainless steel render lath with water 

resistant membrane to stop render 

filling cavity 

25 x 38mm treated timber battens 

at 600mm ctrs fixed vertically to form 

drained cavirty 

TYVEK or similar breathable membrane 

12mm external quality plywood or 

other approved 

Stainless steel stop bead forming drip 

Insect proof mesh (non rust) 

125/150 x 50mm treated stud at 

400mm ctrs 

Thermal insulation as guidance 

details 

13mm vapour checked plaster 

board & skim finish 

125/150 x 50mm sole plates fixed to 

base 

Construction details as 

guidance 

18

External timber framed walls with cladding finish (worst case U-value 0.30- 

suggested U-value 0.18 W/m².k) 

Approved timber/upvc weatherboarding/vertical wall tiling fixed with proprietary rust 

resistant fixings to: 50 X 25mm treated battens/counter battens at 400mm ctrs fixed to: 

Tyvek vapour permeable membrane suitable for timber framed walls & fixed as 

manufacturers details to: 12mm WPB ext quality plywood sheathing (joints covered by 

dpc/battens) fixed to 125/150mm x 50mm head & sole plates and vertical studs (including 

2 rows noggins) at 400mm ctrs, to s/engineers details & calculations. Studs exceeding 

2.5m high to be designed by Structural Engineer. 120mm thick Kingspan Kooltherm K12 

thermal insulation board friction fixed between studs with 12.5mm vapour checked plaster 

board fixed to internal face of studs and finished with 3mm skim coat of finishing plaster. 

All junctions to have water tight construction & seal all perimeter joints with tape internally 

and with silicon sealant externally. 


Diagram 7: Typical section through external timber framed walls with upvc/timber 

weather board finish (not to scale) 

Upvc weatherboarding/vertical wall tiling 

fixed with proprietary rust resistant fixings 

25 x 38mm treated timber battens 

at 600mm ctrs fixed vertically to form 

drained cavirty 

TYVEK or similar breathable membrane 

12mm external quality plywood or 

other approved 

Cladding stop fillet & insect proof mesh 

125/150 x 50mm treated stud at 

400mm ctrs 

Thermal insulation as guidance 

details 


board & skim finish 

125/150 x 50mm soleplates fixed to 

base 

Construction details as 

guidance 

Detached garage with SINGLE SKIN external walls 

External walls to be as elevation plans details using: 100mm brick/reconstituted stone, 

matching painted sand & cement render (render to BS 5262), on 100mm dense concrete 

blocks with 100 X 400mm piers with fair face finish internally at maximum 3.0m ctrs. 

Floor area exceeding 36m2 will require structural engineers details & calculations to 

confirm stability of the structure. 

Eaves level should not exceed 3.0m and ridge height should not exceed 3.6m without 

structural engineers details & calculations to confirm stability of the structure. 

Size and proportion of the garage to comply with paragraph 2C38, and the size and 

location of openings in building to comply with Diagram 18/19/20 of ADA, & briefly as 

follows: 

o Major openings to be restricted to one wall only (normally the front entrance 

garage door(s). Their aggregate width should not exceed 5.0m and their 

height should not exceed 2.1m. 

19

o There should be no other openings within 2.0m of a wall containing a major 

opening. 

o The aggregate size of openings in a wall not containing a major opening 

should not exceed 2.4m2 

o There should not be more than one opening between piers 

o Unless there is a corner pier, the distance from a window or a door to a 

corner should not be less than 390mm. 

o Isolated central columns between doorways (where applicable) to be 325 x 

325mm min. 

o Openings other than those stated above will require structural engineers 

details & calculations to confirm structural stability 

Mortar mix to be 1:1:5-6 or as required by the stone/brick/block manufacturer. 

Diagram 8: Design criteria for small detached single storey garages or similar (not 

to scale) Sizes & proportions of building to comply with Par 2C38 & diagrams 18/19/20 

of ADA 

No other 

openings 

within this 

2.0m zone 

Plan view of garage 

390mm min to 

opening 

piers at 

3000mm 

maximum 

ctrs 

Note: 

The garage floor area should not exceed 36m2 

Piers to be built off the foundations & extend full height of all walls 

& gables 

Maximum roof slope to be 40 degrees, wall plates & gable ends to 

be strapped with galvanized strapped at 2.0m ctrs 

Maximum height to eaves 3.0m & 3.6m to ridge & should not 

exceed 9.0m in length or width 

Note: If any of the above are exceeded, the building is to be 

constructed in compliance with design details & calculations 

from a suitably qualified person which must be approved by 

building control before works commence 

325mm 

min 

325mm 

min 

Pier 

Piers to be 

440mm min 

215mm 

min 

100mm min 

dense 

conc 

blocks or 

bricks 

100mm min 

327mm 

min 

390mm 

min to 

opening 

20

Wall abutments 

Vertical junctions of new and old walls to be secured with proprietary profiled stainless 

steel metal crocodile type system with a continuous cavity fixed with DPC and pointed 

with flexible mastic as manufacturer’s details. 

Lintels & weep holes 

Proprietary manufactured lintels to current British Standards/Euro codes (including 

specialist lintels supporting stone facings) are to be provided over all structural openings. 

The positions, types, sizes, end bearings etc of lintels must be in compliance with the 

lintel manufacturers standard tables suitable for the proposed loadings and clear spans. 

Stop end and dpc trays to be provided above all externally located lintels in compliance 

with lintel manufacturer’s details. Weep holes at 450mm centers with at least two per 

opening. 

Structural columns/beams etc 

Non proprietary beams/columns including pad stone to be fabricated and installed in 

compliance with details and structural calculations carried out by a suitably qualified and 

experienced person, which must be approved by building control before works 

commence on site. Dpc trays to be provided above all externally located beams. Weep 

holes at 450mm centers with at least two per opening. 

Expansion joints 

External walls should be provided with adequately spaced and sized expansion joints, in 

accordance with masonry manufactures details with adequate tying to each side of the 

joint and leaf of masonry using stainless steel wall ties (normally at each block height) 

and sealed externally with a proprietary flexible mastic sealant. (Normally expansion 

joints are 10-12mm wide and spaced vertically at max 12m ctrs in brick work & 6m ctrs in 

block work) 

Strapping and restraint 

Walls to be restrained at intermediate floor, ceiling and gable walls by the provision of 30 

x 5 x 1000mm lateral restraint straps or other approved in compliance with BS EN 845-1, 

at maximum 2m centers carried across at least 3 joists or rafters, etc, with a minimum of 

38mm wide x ¾ depth noggins. 

Cavity Closers 

Proprietary acoustic/insulated fire stop cavity closers, or similar are to be provided to all 

cavity openings/closings, tops of walls and junctions with other properties. 

A3: Separating walls & floors 

( Also see relevant sections in ADE) 

Masonry party walls separating dwellings (U-value 0.2 W/m 2 .K) 

Party walls to be constructed of 2 skins of plastered 100mm dense concrete block with a 

clear 50mm cavity and BBA approved wall ties spaced as external walls up to the 

underside of the roof and fire stopped with mineral wool or an approved proprietary 

intumescent product to achieve a minimum 45dB value for airborne sound insulation.The 

party wall is to be bonded/tied to the inner leaf and the junction of cavities are to be fire 

stopped throughout its length with a proprietary acoustic/ insulated fire stop cavity closer 

and all other vertical and horizontal cavities are to be closed in a similar manner to 

provide effective edge sealing and a U-valueof 0.2 W/m 2 .K. 

21

Timber frame party walls separating buildings (U-value 0.2 W/m 2 .K) 

Timber framed stud walls to achieve a minimum 45 dB value for airborne sound 

insulation and constructed with 100 x 50mm sawn timber studs at 400mm ctrs with 

head & sole plates, with 2x 50mm thick layers ROCKWOOL RWA 45 mineral wool 

friction fixed between studs, and 2x 15mm thick layers of ‘LAFARGE dB check’ wall 

board fixed both sides of stud (joints staggered) with skim coat of plaster finish- as wall 

board manufacturers details. No electrical fittings to be fixed into/onto party walls & all 

gaps to be fire sealed & smoke stopped to the full height and width of the party wall and 

upto the underside of the roof coverings using mineral wool (not glass wool) or an 

approved proprietary intumescent product to provide effective edge sealing and a U 

value of 0.2 W/m 2 .K. 

Party floors separating buildings 

Outside the scope of this guidance- see relevant sections in ADE 

Sound testing requirements 

Pre completion sound testing is required for all new/upgraded party walls/floors which 

must be carried out by a suitably qualified person or specialist to demonstrate 

compliance with Approved Document E and copy of test results sent to building control. 

A4: Additional provisions for 3 storey buildings 

Compressive strength of masonry units 

The compressive strength of bricks and blocks used in three storey construction is as 

follows: 

(i) Outer leaf of cavity wall – Blocks & bricks to be 7N/mm2 from foundation level upto the 

underside of the structural roof. 

(ii) Inner leaf of cavity wall – Blocks to be 7N/mm2 from foundation level upto the 

underside of the first floor level. Blocks above this level upto the underside of the 

structural roof can be 2.8N/mm2. 

(iii) Internal walls – Blocks to be 7N/mm2 and 140mm thick upto the underside of the first 

floor level. Blocks above this level upto the underside of the structural roof to be 

2.8N/mm2. 

22

A5: Internal partitions 

Internal load bearing masonry partitions 

Internal load bearing walls to be minimum100mm thick 7N/mm2 dense concrete blocks 

(actual wall thickness must not be less than the wall it supports above), built off suitable 

foundations (as detailed above), with pre-cast concrete/proprietary steel lintels over 

openings (in compliance with lintel manufacturers span tables) and walls bonded/tied to 

external or party walls with proprietary ties each course and restrained by floor or ceiling 

joists/trusses. 

Internal load bearing timber stud partitions 

Load bearing timber stud partitions and non-proprietary lintels to be in compliance with 

details and calculations by a suitably qualified and experienced person, which must be 

approved by building control before works commence on site. 

Internal masonry non-load bearing partitions 

Internal non-load bearing partitions to be constructed of 100mm 2.8/mm² dense concrete 

blocks built off a thickened floor slab and tied/block bonded to all internal and external 

walls at maximum 225mm centers with either a plaster or dry lined finish as the external 

walls. 

Internal timber studwork non-load bearing partitions 

Non-load bearing stud partitions are to be constructed of 100 x 50mm soft wood with 

head and sole plates and intermediate noggins fixed at 600mm with a minimum of 25 

mm of 10Kg/m 3 proprietary sound insulation quilt suspended in the stud and finished with 

15 mm plasterboard and skim both sides. 

23

A6: Intermediate upper floor(s) 

Floor to be constructed of kiln dried structural grade timber joists with sizes and spacing 

suitable for the proposed clear span as annotated on the drawing or in compliance with 

Tables below. Joists to be supported by heavy-duty proprietary galvanized metal restraint 

joist hangers built into walls or fixed to treated timber wall plates (same sizes as joists) 

resin bolted to walls at 600mm centers using approved 16mm diameter stainless steel 

fixings. Alternatively, joists can be built into walls using approved proprietary sealed joist 

caps. Joists are to be doubled up and bolted together for trimmers, under partitions and 

baths. Ensure all gaps & all voids are sealed to prevent any air leakage. 

Floor void between joists to be insulated with a minimum thickness of 100 mm of 

10Kg/m³ proprietary sound insulation quilt, ceiling to be a minimum 15mm plasterboard 

and skim and floor joist covering to be a minimum of 20mm softwood tongue and groove 

softwood boards or moisture resistant particle/chipboard to give overall 30 minutes fire 

resistance. Floor joists to be provided with 1 row of 38 x ¾ depth solid strutting at ends 

between joist hangers or proprietary galvanized struts to BS EN 10327 fixed as 

manufacturers details, at mid span for 2.5 – 4.5m spans and 2 rows at ¹/3 points for 

spans over 4.5m. 

Table 3: Spans for Common Domestic Floor Joist Sizes (Strength Class C24) 

Size of joist 

Breadth X Depth 

(mm) (mm) 

47 97 

47 120 

47 145 

47 170 

47 195 

47 220 

75 220 

Spacing of joist (mm) 

400 450 600 

Maximum clear span (m) 

2.12 2.01 1.75 

2.70 2.59 2.34 

3.25 3.13 2.84 

3.81 3.66 3.32 

4.36 4.19 3.81 

4.84 4.70 4.29 

5.41 5.26 4.91 

Table 4: Spans for Common Trimmer Joist supporting Trimmed Joists 

(Strength Class C24) 

Length of trimmed joists (m) 

1.0 2.0 3.0 4.0 

Size of trimmer (mm) Clear span of trimmer joist (m) supporting 

2 x 47 x 145 

2 x 47 x 170 

2 x 47 x 195 

2 x 47 x 220 

2 x 75 x 220 

trimmed joists 

2.68 2.27 1.97 1.68 

3.21 2.68 2.33 1.99 

3.69 3.09 2.69 2.31 

4.17 3.50 3.06 2.62 

4.81 4.13 3.62 3.21 

Table 5: Spans for Common Trimming Joist supporting Trimmer Joist 


Length of trimmer joist (m) 

1.0 2.0 3.0 max 

Size of trimming joist Clear span of trimming joist (m) supporting 

(mm) 

2 x 47 x 145 

2 x 47 x 170 

2 x 47 x 195 

2 x 47 x 220 

2 x 75 x 220 

trimmer joist 

2.62 2.42 2.25 

3.08 2.84 2.65 

3.54 3.27 3.05 

3.99 3.70 3.46 

4.66 4.32 4.05 

24

Sound insulation to floors within the dwelling 

Intermediate floors to be provided with sound insulation as described in the relevant floor 

section in this document. 

SVP pipe boxing 

SVP pipe boxing to consist of soft wood framing, 2 layers of 15mm plasterboard and skim 

and void filled with mineral wall quilt for sound insulation and fire/smoke stopping. Boxing 

to be continuously carried up to roof space for soil and vent pipe and provided with air 

grills where an air admittance valve is used. Ensure all gaps & all voids are sealed to 

prevent any air leakage. 

Exposed intermediate upper floors 

Semi exposed intermediate timber floors over unheated areas such as garages, porches, 

walkways, and canopy’s to be insulated with the following minimum thickness and types 

of insulations to achieve a U-value0.22w/m².k as in Table 6 below. Where the 

construction is open to the environment a vapour barrier and proprietary external mineral 

fiber or similar 30 minute fire and moisture resistant boarding is to be applied to the 

underside of the floor. 

Diagram 9: Typical section through an upper floor (not to scale) 

Double glazed window bedrooms/ 

inner rooms to be fitted with openings 

suitable for escape as detailed in 

the specification 

100mm minimum width insulation block (see 

options in specification) 

Wall grade insulation (see options in 


50mm clear cavity if using partial fill cavity 

wall insulation (see options in specification) 

Wall ties and spacings as detailed in 

specification 

100mm minimum width external wall in 

materials to match existing or as specified in 

planning permission 

Proprietary insulated steel lintels (with dpc 

trays and stop ends) suitable for clear spans 

and loadings in compliance with lintel 

manufactures standard tables 

Damp proof course 

and insulated closer 

Galvanized steel 

straps at 2m ctrs built 

into cavity and fixed 

over 3 joists with 

noggins 

Floor joists doubled 

up under partition 

walls & baths 

Sound insulated plaster 

board achieving 30 

minutes fire resistance 

Sound insulated stud partition 

22mm t & g moisture resistant floor boarding 

Strutting between joist (see 

specification for spacings) 

Floor joists (see construction 

details and table in 

specification for sizes of joists 

suitable for clear spans) 

Sound insulation quilt 

as specification 

100mm dense 

concrete partitions 

precast 

concrete/proprieteray 

steel lintols, sizes 

suitable for clear spans 

as manufactures 

standard tables 

Table 6: Insulation requirements to exposed intermediate floors 

(worst case U-value 0.25-suggested U-value 0.13 W/m².k) 

Insulation Type Minimum Thickness Required 

Kingspan Kooltherm K3 or 

125mm (floor P/A ratio of 0.5) 

other approved with K value of 0.020 


25

A7: Pitched roofs 

Pitched roof coverings 

Roof covering to consist of slate or tile and associated capping, verge/eaves details fixed 

in accordance with manufacturer’s details for pitch and exposure as detailed on the 

drawings. Cladding to be fixed to a minimum 25 x 50mm treated timber batten or to 

manufacturer’s directions and roof timbers to be overlaid with un-tearable breathable/non 

breathable roof felt underlay to BS 747 or relevant BBA certificate. 

Roof to be formed from kiln-dried stress graded timbers sized, spacing, spans, bracing 

and fixings as detailed on the drawing or tables below. Alternatively, the roof may be 

formed from proprietary prefabricated manufactured trusses/attic trusses and bracing to 

BS 5268 but both with a foil backed 12.5mm plasterboard and skim ceiling finish. 

Pitched roof structure 

Roof to be constructed using either manufactured roof trusses or a cut roof as follows: 

Roof trusses (including attic & girder trusses) 

Roof to be constructed using specialist designed and manufactured trusses (or Attic 

trusses where forming room in the roof) @ 600ctrs (max) to BS 5268:3 1985 A2 94. 

Trusses to be fixed and braced strictly in accordance with manufacturers details and 

mechanically fixed to 100 x 50mm sw treated wall plates via galvanized steel truss clips. 

Reinforced concrete pad stoned required to support girder trusses to details and 

calculations by a suitably qualified person. 

The person carry out the building work is to check and confirm the actual roof pitch to the 

truss manufacturer prior to placing an order. 

Details of trusses to be prepared by specialist designer/manufacturer, submitted and 

approved by building control prior to commencing roof construction. 

Cut roof construction 

Roof to be constructed using kiln dried –stress graded timber. Rafters, ceiling joists, 

purlin, hanger and binder sizes as stated on tables below or see TRADA Span Tables- 

suitable for the proposed clear spans and all properly fixed together using approved 

fixings. 

Where the ceiling joists are raised above wall plate level they must be fixed within the 

bottom third of the rafter using 12mm diameter high tensile bolts and steel toothed 

connectors to connect each rafter and ceiling joist to prevent possible roof spread. Joists 

raised above this level are to be designed by a suitably qualified person and approved by 

building control before works commence. 

Struts & braces to be 100 X 50mm, hips to be splayed rafter depth + 25mm (under 30 

degree pitch the hips are to be designed by a suitably qualified person), lay-boards to be 

the splayed rafter depth + 25mm X 32mm thick, ridges to be splayed rafter depth + 

25mm, all valleys beams are to be designed by a suitably qualified person, wall plates to 

be 100 x 50 fixed to inner skin of cavity wall using galvanized strapping as detailed 

below. Hip rafters to have 100 X 75mm angle ties connected across wall plates in 

housed joints at corners of roof & hip irons screwed to hip rafters. 

Soffits, fascias and barge boards etc to match the existing or in UPVC to BS 4576, 

fixed in compliance with manufacturers details. 

26

Allow for all necessary alteration/modification of any existing adjoining roof as required to 

enable the proper completion of the works and in agreement with building control. 

Allow for building in as work proceeds or insertion of proprietary stepped/cavity tray dpc 

to follow line of new roof 150mm above all roof/wall abutments as necessary using code 

5 lead flashings. Tie new roof into the existing, alter/modify/renew existing roof coverings 

and form a weather tight structure. 

Fix 12.5mm foil backed plasterboard (joints staggered) and 5mm skim coat of finishing 

plaster to the underside of all ceilings using galvanized plasterboard nails. 

Roof pitch to (single storey) single skin buildings with walls 100mm thick should not 

exceed 40 degrees without structural engineers details & calculations to confirm stability 

of the structure. Cut roofs over 40° are to be braced to BS 5268. 

Diagram 10: Typical section through a pitched roof (not to scale) 

Roof slates/tiles to match existing or as stated in planning permission 

fixed as manufacturers details and suitable for the pitch 

Breathable or non breathable roofing felt fixed as 

manufacturers details 

25 x 50mm treated battens at a guage to suit coverings 

Rafters (see construction details and table 

in specification for sizes of rafters suitable for 

clear spans) 

Ceiling joists (see construction details and table 

in specification for ceiling joist sizes suitable 

for clear spans 

Rain water gutter 

Facia/soffit boards 

Eaves ventilation equal 

to a continuous 10mm 

air gap with insect screen 

(may not be required 

with certain breathable 

roof membranes) 

Double glazed window bedrooms/ 

inner rooms to be fitted with openings 

suitable for escape as detailed in 

the specification 

Table 7: Spans for Common Domestic Timber Rafter Sizes at 400mm spacing 


Slope of Roof (degrees) 

15-22 22-30 30-45 

Size of Rafter 


Breadth X Depth (mm) 

47 100 

47 125 

47 150 

47 170 

47 195 

Wall plates 

(strapped at 

2.0m ctrs) 

Continuous 

insulation 

Sound insulated 

stud partition as 

detailed in 

specification 

Proprietary insulated steel lintels suitable for spans and 

loadings in compliance with lintel manufactures 

standard tables 

NOTE: Proprietary high level roof vents to be installed 

where insulation follows slope of roof- equal to a 

continuous 5mm air gap with insect screen 

Ridge tiles to match roof coverings 

Ridge board (see specification for details) 

Hangers to support hangers if additional support is 

required to ceiling joists (contact building control for 

details) 

Binders to support ceiling joists if they require additional 

support (contact building control for details) 

Roof insulation (see options in specification 

Galvanized steel strapping at 2m ctrs built into 

cavity and fixed over 3 rafters with noggins as 

detailed in specification 

Vapour checked plaster board 

2.52 2.58 2.66 

3.15 3.22 3.32 

3.76 3.85 3.97 

4.36 4.45 4.57 

4.87 4.98 5.14 

27

Table 8: Spans for Common Domestic Timber Ceiling Joist Sizes at 400mm 

spacing (Strength Class C24) 

Size of Ceiling Joist 


Breadth X Depth (mm) 

47 97 

1.93 

47 120 

2.56 

47 145 

3.37 

47 170 

4.00 

47 195 

4.73 

47 220 

5.47 

Table 9: Spans for Common Domestic Timber Purlin Sizes (Strength Class C24) 

Slope of Roof (degrees) 

Size of Purlin 


(mm) 

75 125 

75 150 

75 175 

75 200 

75 225 

15-22 22-30 30-45 

Spacing of Purlins (mm) 

1500 1800 2100 1500 1800 2100 1500 1800 2100 


1.87 - - 1.91 - - 1.98 1.86 - 

2.24 2.10 1.99 2.29 2.15 2.04 2.37 2.23 2.11 

2.61 2.45 2.32 2.67 2.51 2.38 2.76 2.59 2.46 

2.98 2.80 2.65 3.05 2.87 2.71 3.16 2.96 2.81 

3.35 3.15 2.98 3.43 3.22 3.05 3.55 3.33 3.15 

Table 10: Permissible Clear Spans for Common Ceiling Binders Sizes 


Size of Binder 


(mm) 

47 150 

47 175 

63 150 

63 175 

75 150 

75 175 

Spacing of Binders (mm) 

1200 1500 1800 2100 2400 2700 


2.19 2.06 1.96 1.87 1.80 - 

2.60 2.45 2.32 2.22 2.13 2.05 

2.45 2.31 2.20 2.10 2.02 1.95 

2.91 2.74 2.60 2.48 2.38 2.30 

2.62 2.47 2.35 2.25 2.16 2.08 

3.11 2.92 2.77 2.65 2.55 2.46 

Roof restraint 

Roof and walls to be provided with lateral restraint straps across at least 3 timbers as 

noted in wall section at ceiling, wall plate and verge levels with 30 x 5mm x 1m 

galvanized metal straps or other approved to BSEN 845-1 at maximum 2m centers. 

Roof insulation 

Insulation to be fixed to manufactures details and must be continuous with the wall 

insulation but stopped back at eaves or at junctions with rafters to allow a 50mm air gap 

in ventilated cold roofs. 

Table 11: Insulation laid horizontally between and over ceiling joists 

(worst case U-value 0.20-suggested U-value 0.13 W/m².k) 

Product K -Value Position in roof 

Crown Wool & 0.036 200mm between joists & 

Rock-wool Roll 


200mm laid across joists 

28

Table 12: Insulation fixed between/under rafters 

(worst case U-value 0.20- suggested U-value 0.13 W/m².k) 


Kingspan Kooltherm K7 0.020 100mm friction fixed between 

rafters* & 

Kingspan Kooltherm K18 0.020 82.5mm fixed under rafters 

Or other approved with a K 

value of 0.020 


* Where rafters are only 100mm deep, battens should be provided to their 

underside to maintain a 50mm air gap above the insulation where a non 

breathable roofing felt is used or battened to allow a 25mm sag in felt if using a 

breathable roofing membrane as the manufacturers details. 

Table 13: Insulation fixed between/over rafters 

(worst case U-value 0.20- suggested U-value 0.13 W/m².k) 


Kingspan Kooltherm K7 




0.020 75mm fixed between rafters & 

80mm fixed over rafters 

25 x 50mm counter battens to be fixed over insulation to allow for sag in 

breathable roofing membrane as manufacturers details 

Diagram 11: Typical roof valley detail (not to scale) 

125mm 

min 

Rafter birds 

mouthed over 150 x 

50mm wall plate 

(wall plated 

strapped at 2.0m 

ctrs 

Pcc pad stone or 

dense blockwork 

200mm 

min 

Roof coverings & roof structure as 

specification 

& section details 

Breathable roofing membrane 

lapped over lead & forming drip 

Tiling fillet 

Code 5 lead lined gutter- lead sizes, 

drips & welted joints etc to the Lead 

Development association details 

25mm treated gutter board fixed to: 

50 x 50mm treated timber gutter 

bearer 

29

Diagram 12: Typical section through a dormer roof (not to scale) 

Trimming 

joists as 

spec 

Rain water gutter, facia/soffit 

boards etc as spec 

Eaves ventilation equal 

to a continuous 10mm 

air gap with insect screen 

(may not be required 

with certain breathable 

roof membranes) 


board & skim 

Roof slates/tiles to match existing or as stated in 

planning permission fixed as manufacturers details and 

suitable for the pitch 

25 x 50mm treated battens at a guage to suit coverings 

Breathable or non breathable roofing felt fixed as 

manufacturers details 

Ridge board as specification 

Rafters (see construction details and 

table in specification for sizes of rafters 

suitable for clear spans) 

Ceiling joists (see construction details 

and table in specification for ceiling 

joist sizes suitable for clear spans 

Insulation deatils as tables in 

specification 

Dormer walls constructed with painted 

renders or cladding on insulated 

timber frame as spec details 

Code 5 lead flashing & valleys 

Dormer roof supported on rafters 

doubled up & bolted together 

See main roof for 

construction details 

Ventilation to pitched roofs 

Roof insulation to be continuous with the wall insulation but stopped back at eaves or at 

junctions with rafters to allow a 50mm air gap. Cross ventilation to be provided by a 

proprietary eaves ventilation strip equivalent to a 25mm continuous gap at eaves level 

with insect grill. 

Alternatively, where cross ventilation is not possible such as mono pitch, coved ceiling or 

room in the roof provide additional ridge/high level ventilation equivalent to a 5mm gap in 

the form of proprietary vent tiles spaced in accordance with manufacturer’s details. 

Ventilation to the roof space may be omitted, only if a proprietary BBA or similar 

approved breathable roof membrane, with minimum 25mm thick treated vertical counter 

battens and proprietary eaves carrier system is used. Breathable roof membranes & 

proprietary roof vents must always be installed as manufacturers details (note: some 

breathable membranes may also require additional roof ventilation) 

30

A8: Flat roof construction 

Flat roof to be carried out as detailed on the drawings. Moisture content of timber should 

not exceed 20% and to be kiln dried & grade C24. Workmanship to comply to BS 8000:4. 

All fixings to be proprietary stainless steel or galvanized steel. 

Waterproof covering to be either: 

3 layers of high performance felt (hot bonded together with bitumen) to a current 

BBA Certificate in compliance with BS8217 

Single layer system with a current BBA or WIMLAS Certificate 

Glass reinforced plastic (GRP) system with a current BBA or other approved 

accreditation 

Lead sheet fixed in compliance with the Lead Development Associations guide to 

good practice 

Mastic asphalt fixed in compliance with the Mastic Asphalt Councils technical 

guides & specifications 

Waterproof covering to be laid in compliance with manufacturers details by flat roofing 

specialist onto separating layer over roof insulation layer in compliance with below to 

form a ‘warm roof’ (or alternatively insulation fixed between/under joists in compliance 

with Table below forming a ‘cold roof’) fixed to, 22mm external quality plywood decking or 

similar approved laid to 1:60/80 minimum gradient using firing strips at spacing to match 

joists, fixed onto timber flat roof joists constructed of kiln dried structural grade timber 

with sizes and spacing suitable for the proposed clear span as annotated on the drawing 

or in compliance with Table below or see TRADA Span Tables. 

Flat roof to have a surface finish of bitumen bedded stone chippings covering the whole 

surface to a depth of 13mm to achieve a class AA (or B (t4) European class) fire rated 

designation for surface spread of flame. 

Restrain flat roof to external walls by the provision of 30 x 5 x 1000mm lateral restraint 

straps at maximum 2000mm centers fixed to 100 x 50mm wall plates and internal wall 

faces 

Flat roof insulation to be in compliance with tables below. Flat roof insulation is to be 

continuous with the wall insulation but stopped back to allow a continuous 50mm air gap 

above the insulation in ventilated cold decks. Cross ventilation to be provided on 

opposing sides by a proprietary eaves ventilation strip equivalent to a 25mm continuous 

gap at eaves level with insect grill. Note: Warm roof applications i.e. insulation above the 

structural deck do not require ventilation. 

The design, workmanship & selection of materials should comply with Model 

Specification Sheet P.L.1 Built-Up Roofing: Plywood Deck, published by The British Flat 

Roofing Council. Metallic roof trims to be of non-corrodible material & resistant to sunlight 

& not fixed through the water proof covering. All timber to be treated using CCA 

vacuum/pressure or O/S double vacuum to BS 5268:5, including all cut ends of timber 

etc 300mm of any joint. 

All flat roofing works to be carried out by a specialist flat roofing contractor and all 

materials etc to be fitted in compliance with manufacturer’s details. Work should not be 

carried out during wet weather or when the deck has not fully dried out. A 500g vapour 

control barrier is required on the underside of the roof below the insulation level. Fix 

12.5mm foil backed plasterboard (joints staggered) and 5mm skim coat of finishing 

plaster to the underside of all ceilings using galvanized plasterboard nails. 

31

Table 14: Spans for Common Flat Roof Joist Sizes (Strength Class C24) 

(Access for maintenance and repairs only) 

Size of joist Spacing of joist (mm) 

Breadth x Depth 400 450 600 

(mm) 


47 97 2.02 1.99 1.90 

47 120 2.65 2.61 2.46 

47 145 3.36 3.27 2.97 

47 170 3.98 3.83 3.48 

47 195 4.55 4.38 3.98 

47 220 5.13 4.93 4.49 

75 220 5.94 5.73 5.23 

Table 15: Insulation Fixed Between/Under Flat Roof Joists 

(Vented cold roof-worst case U-value 0.20- suggested U-value 0.13 W/m².k) 


Kingspan K7 

Kingspan K18 

Or other approved with a 

K value of 0.020 

0.020 

0.021 

200mm between joists 

32.5mm fixed under joists 

Note: The joist depth must be sufficient to maintain a 50mm air gap above the 

insulation and cross ventilation to be provided on opposing sides by a 

proprietary ventilation strip equivalent to a 25mm continuous gap at eaves level 

with insect grill for ventilation of the roof space. 

Table 16: Insulation Fixed above Flat Roof Joists 

(Non vented ‘warm roof’ worst case U-value 0.20-suggested U-value 0.13 W/m².k) 

Product K -Value Insulation fixed above deck 

Kingspan Thermaroof 




0.020 180mm fixed above deck in a single 

layer 

32

Diagram 13: Typical section through a flat (cold) roof (not to scale) 

Welted drip 

25mm continuous air gap 

with insect screen 

wall plate & strapping as 

spec details 

Cavity wall as spec details 

1:60/80 gradient 

13mm diam stone chippings bedded in hot bitumen 

Flat roof joist sizes and spacing as 

spec tables 

Proprietary steel box beam as 

manf details suitable for clear span 

or timber lintel to s/engineers 

details & calculations to suit clear 

spans of openings 

Water proof coverings applied by flat roofing specialist as spec. 

External quality structural decking 

Note: if insulation is fixed above the structural deck (forming a 

warm roof) the above ventilation details can be omitted 

Firing strips at 1:60 min gradient 

50mm min air gap 

Thermal insulation fixed above or below structural 

decking as guidance tables 

Plasterboard with vapour check 

Welted drip 

Rain water gutters, facia/ 

barge board 

25mm continuous air gap 

with insect screen 

Valleys and lead work 

Lead work, flashing, soakers, valleys and gutters, etc, to be formed from Code 5 lead 

sheet and fully supported on treated valley boards, etc, and to have a minimum 150mm 

lap joints, dressed 200mm under tiles, etc, and not to be fixed in lengths exceeding 1.5m 

and to be fixed in accordance with the roof cladding manufacturers and the Lead 

Development Association recommendations. 

Lofts hatches, doors & Light wells to roof spaces 

All hatches, doors and light wells in the roof space to be insulated to the same standard 

as the roof, draft stripped and positively fixed. All hatches to be accessible. 

33

Part B: Fire safety & means of escape 

Smoke /heat alarms 

All floors to be provided with mains operated interconnected fire detection and fire alarm 

system to BS 5446 & installed in accordance with the relevant recommendations of 

BS 5839 – 6: 2004 to at least a Grade D Category LD3 standard. Self contained mains 

operated smoke alarms (heat alarms installed in kitchens if open to stairway) with battery 

back up to be fixed at ceiling level in all circulation areas at each storey level, within 7.5m 

of all doors to habitable rooms. 

Means of escape windows 

Means of escape windows to be fitted with proprietary hinges to open to the minimum 

required clear width of 450mm. Escape windows must have minimum clear opening 

casement dimensions of 0.33m² and 450mm (typically 450mm wide x 750mm high), 

located within 800-1100mm above floor level to all bedrooms and habitable rooms at 1st 

floor level and inner habitable rooms on the ground floor. Windows above the ground 

floor storey and within 800mm of floor level are to be provided with containment/ 

guarding/ proprietary catches which should be removable (child proof) in the event of a 

fire. Where escape windows cannot be achieved, direct access to a protected stairs (or 

protected route to inner rooms) is acceptable in compliance with ADB1- par 2.6 (a) or (b). 

Fire doors & frames 

Walls between garage and the house to be built up off foundations in masonry to give 30 

minutes fire resistance and taken upto the ceiling/roof level and fire stopped with mineral 

wool. Door(s) between the house and garage to be FD30 to BS476-22:1987 fitted with 

proprietary mechanical self-closers, intumescent strips and smoke seals. 

Means of escape from basements 

If the basement storey in served by a single stairway and contains a habitable room, the 

basement should be either fitted with a means of escape window or door in compliance 

with this guidance or a protected stairs leading from the basement to the final exit in 

compliance with this guidance. 

Permitted building openings in relation to a boundary: 

Openings within 1.0m of a boundary 

An unprotected opening of 1m 2 (e.g. window) is permitted every 4.0m on the same 

building face. This unprotected opening can consist of two or more smaller openings 

within an area of 1m 2 (openings less than 0.1m 2 is permitted every 1500mm on the same 

building face). There are no restrictions on dimensions between openings separated by 

compartment walls & floors. Please refer to Diagram 20 of ADB4 Volume 1 for full details. 

Openings more than 1.0m from a boundary 

Permitted unprotected openings to be in compliance with table below for buildings not 

exceeding 3 storeys high (excludes basements) or more than 24m long. 

Table 17: Permitted unprotected areas in relation to a relevant boundary 

Minimum distance between side of 

Maximum total area of unprotected 

building & relevant boundary 

openings 

1.0m 

5.6m2 

2.0m 

12m2 

3.0m 

18m2 

4.0m 

24m2 

5.0m 

30m2 

6.0m 

no limit 

34

If sprinklers are fitted throughout the building to BS 9251, the above distances can be 

reduced by 50% (min 1.0m) or the unprotected opening area doubled. Please refer to 

ADB4 Volume 1 for full details relating to space separation and other methods of 

calculating unprotected areas. 

Fire resistance to elements of structure etc 

Please refer to Table A1: Appendix A of ADB: Volume 1 for full details. 

Table 18: Fire resistance to common elements of structure etc 

Building element Fire resistance 

in minutes 

Method of protection 

Beam, column or frame 30 All exposed faces 

Load bearing wall 30 Each side separately 

Upper floors (Max 3 storey building) 30 Underside 

Roof (only if forming part of an escape route) 

External walls: 

30 Underside 

(i) Less than 1.0m to relevant boundary 

(ii) More than 1.0m to relevant boundary 

60 

Each side separately 

(max 3 storey building) 

Walls & upper floors separating an integral 

30 

From inside building 

garage from the dwelling 

Compartment walls & floors separating 

30 

From garage side 

Dwellings 

Protected stairs & lift shaft (not forming 

60 


part of a compartment wall) 

30 


Cavity barriers etc 30 Each side separately 

Note: 12.5mm plasterboard & skim finish applied to 100 x 50mm timber stud partitions/ 

ceiling/ floor joists as detailed in this specification will achieve 30 minutes fire resistance, 

two layers of 12.5mm plaster board (joints staggered) will achieve 60 minutes fire 

resistance. Masonry walls detailed in this specification will achieve 60 minutes fire 

resistance. 

Surface spread of flame: wall & ceiling linings 

Table 19: Surface spread of flame: Classification of wall & ceiling linings 

Please refer to Table 1: Section 2 of ADB: Volume 1 for full details. 

Location National class European class 

Small rooms upto 4m2 & 

Domestic garages upto 

40m2 

3 D-s3,d2 

Other rooms over 4m2 inc 

Garages over 40m2 & 

Circulation spaces within 

Dwellings (e.g. hall, stairs 

& landings) 

1 C-s3,d2 

Note: Plaster on masonry walls & plaster board & skim linings in this specification will 

achieve class 1. Exposed timber linings should be treated with a proprietary treatment to 

achieve the above classifications. 

35

Additional fire safety & means of escape provisions for new 3 storey dwellings 

The stairs is to be protected & enclosed by 30 minutes fire resisting and fire insulating 

construction to the walls and partitions constructed in compliance with the relevant 

paragraph above. 

FD20 fire doors to BS476-22:1987 fitted with an intumescent strip rebated around top & 

sides of door or frame/lining. The exit from the stairway should extend direct to a final exit 

and to outside air. 

All floors to be provided with mains operated interconnected smoke alarms at ceiling 

level with battery back up in compliance with the relevant paragraph above. 

Limitations on the use of un-insulated glazed elements on escape routes to be in 

compliance with Table A4 of Approved Document B: Volume 1- Dwelling Houses. 

Residential sprinkler systems for means of escape 

Where fire safety requirements of the building regulations cannot be met for new 

dwellings, proposals for fire engineered solutions may be allowed against the 

requirements of Approved Document B where a risk assessment has been carried out by 

a suitably qualified and experienced fire engineer and approved by building control 

before works commence on site. The residential sprinkler system is to be designed and 

installed to BS 9251:2005 incorporating BAFSA technical guidance note No.1 June 2008 

by a suitably qualified specialist- which must be approved by Building Control before 

works commence on site. 

If the condition not being met is a ground floor open plan arrangement and the stairs 

discharge into a habitable open plan area then a partial sprinkler installation to the whole 

of all connected open plan areas may be used. Fire separation of the route will be 

required from the upper floor from this open plan area with a 30 minute fire resisting 

partition and FD20 fire door fitted with intumescent strips. Instead of the separation it may 

be possible to fully sprinkler the whole dwelling and retain the open plan arrangement 

with the agreement of building control. 

With the agreement of the building control, it should be possible to reduce fire protection 

throughout the dwelling by 30 minutes with the introduction of a full sprinkler installation. 

Contact: The British Automatic Sprinkler Association (BAFSA)- Sprinklers for Safety: Use 

and Benefits of Incorporating Sprinklers in Buildings and Structures (2006) ISBN: 0 

95526 280 1. See also: www.bafsa.org.uk ISBN 0-9552628-3-6 technical guidance note 

no.1 see also www.firesprinklers.org.uk 

IMPORTANT NOTE: The above requirements for three storey dwellings need not be 

followed if the dwelling house has more than one internal stairway, which afford effective 

alternative means of escape and are physically separated from each other. 

36

Part C: Site preparation and resistance to contaminants & moisture 

Horizontal damp proof courses & trays (dpc’s) 

Horizontal Dpc’s and Dpc trays with weep holes at 1.0m ctrs to be provided 150mm 

above ground level continuous with and sealed to the floor Dpm & radon dpc tray. 

Vertical damp proof courses & trays etc (dpc’s) 

Stepped and horizontal Dpc/cavity trays are to be provided over all openings, roof 

abutments/projections and over existing walls with different construction or materials. 

Install vertical dpc or proprietary insulated cavity closers at all closings, returns, 

abutments to cavity work and openings etc. 

Radon gas protection in sub structures 

Full radon protection is required in the sub structure to prevent radioactive gas present in 

the sub soil from entering the building through cracks in the construction as detailed 

below, unless it is confirmed by a radon risk report from a specialist (available from 

www.ukradon) that full radon protection is not required. 

Note: basic radon protection is required as a minimum standard in all sub structure floors 

as detailed in Part A and relevant diagrams of this guidance. 

3 alternative methods for providing full radon gas protection in sub structures 

(i) Proprietary plastic radon sumps to be installed in sub floor of ground bearing slab as 

manufacturers details (see www.visqueenbuilding.co.uk) and diagram 2 above. Sumps to 

be connected to 110mm diameter proprietary air sealed upvc pipes, and fitted with an 

access plug cap above ground level to allow connection to a radon fan & duct system- 

upto eaves level of the building. A sign identifying radon pipe work is to be fixed to the 

wall above the capping. 1200g DPM radon barrier is to be taped and sealed at all joints, 

junctions, service entry points and sealed to a continuous cavity tray (using a proprietary 

tape) which is supported by the cavity infill at ground level and brought through the 

external wall leaf with weep-holes to the external skin; Or 

(ii) Proprietary geo-textile drainage matting or duct system laid beneath slabs as 

manufacturers details & connected to an extract pipe & fan system as detailed above; Or 

(iii) Construct ventilated beam & block floor as detailed in diagram 3 above. 

Further advice on radon & radon protection can be obtained from BRE at: www.bre.co.uk 

& The Health Protection Agency at: www.hpa.org.uk 

Methane gas & other gas protection in sub structure 

Protection is to be provided in the sub structure in compliance with the provisions for full 

radon protection in item above and in the following circumstances: 

(i) Within 250m of a landfill site. (The Environment Agency’s policy on building 

development on or near landfill sites should be followed). 

(ii) On a site containing biodegradable substances (including made up ground or fill); or 

subject to use that could have petrol oil or solvent spillages; or naturally occurring 

methane, carbon dioxide and other hazardous gases (e.g. hydrogen sulfide). 

Information regarding land contamination can be obtained from your local authority 

environmental health department. Risk assessments, ground investigations and any 

necessary remedial works should be carried out in compliance with Approved Document 

C of the Building Regulations. 

37

Tanking systems 

Suitable tanking systems include asphalt, self adhesive bitumen membranes, drained 

cavity membranes and liquid applied membranes to have BBA or other approved 

accreditation and assessed by a tanking specialist as suitable for the proposed situation. 

Tanking systems to be installed/applied by a tanking specialist in compliance with tanking 

manufacturers details which must be approved by building control before works 

commence on site. 

Flood risk 

Flood risk should be assessed and precautions carried out in compliance with paragraph 

0.8 of ADC 

Part D: Cavity wall filling with insulation by specialists 

The suitability of the cavity wall for filling must be assessed before the works is carried 

out by an insulation specialist in accordance with BS 8208: Part 1: 1985. 

The insulation specialist carrying out the work must hold or operate under a current BSI 

Certificate of Registration of Assessed Capability for the work being carried out. 

The insulation material must be in accordance with BS 5617: 1985 and the installation 

must be in accordance with BS 5618: 1985 

The Installation of urea-formaldehyde (UF) in cavity walls is to be carried out in 

compliance with paragraphs 1.1 — 1.2 of ADD1 

38

Part E: Resistance to the passage of sound 

Performance standards 

Party walls and floors separating new dwelling/flats. 

Sound insulation details for new party walls and floors to be carried out in accordance 

with the relevant details contained within this guidance and Approved Document E as 

follows: . 

45 dB minimum values for airborne sound insulation to walls, floors & stairs; & 

62 dB maximum values for Impact sound insulation to floors & stairs. 

Party walls and floors separating conversion of buildings into new dwellings/flats 

Sound insulation details for new party walls and floors to be carried out in accordance 

with the relevant details contained within this guidance and Approved Document E as 

follows: . 

43 dB minimum values for airborne sound insulation to walls, floors & stairs; & 

64 dB maximum values for Impact sound insulation to floors & stairs. 

Exemptions/ relaxations for conversion of historic buildings into dwellings/flats 

If the proposed sound insulation requirements will unacceptably alter the character or 

appearance of a historic/listed building then the sound insulation standards may be 

exempt or improved to what is reasonably practical or acceptable standard that would not 

prejudice the character or increase the risk of deterioration of the building fabric or fittings 

in consultation with the local planning authorities conservation officer. A notice showing 

the actual sound test results is to be fixed in a conspicuous place inside the building in 

compliance with paragraph 0.7 of ADE 

Pre completion sound testing 

Robust details to be adopted or pre-completion sound testing to be carried out to 

demonstrate compliance with ADE1 as follows: 

(i) Robust details 

Robust Construction Purchase Certificates are to be provided by the building owner on 

commencement and provide compliance certificates on completion; which must be sent 

to Building Control to demonstrate compliance with ADE1. Robust Construction Details 

can be obtained through Robust Details Ltd. Tel: 0870 240 8210. 

(ii) Pre completion sound testing by specialist 

Pre completion sound testing is to be carried out by a suitably qualified person or 

specialist with appropriate third party accreditation (UKAS or ANC registration) to 

demonstrate compliance with ADE1, and copy of test results sent to building control. 

Testing rate requirements 

At least one set of recorded tests is required for every 10 new dwellings on the same site 

and additional testing may be required where requested by building control. 

Remedial works and re-testing 

Remedial works and re-testing will be required where the test has failed, in compliance 

with Section 1 of ADE 

New Internal walls & floors 

Sound insulation details between internal walls & floors separating bedrooms or a room 

containing a WC and other rooms to be carried out in accordance with the relevant 

details contained within this guidance and Approved Document E . 

39

Part F: Ventilation to new dwellings 

Ventilation systems 

System 1: Purge (natural) ventilation Background ventilation & intermittent extract fans in 

compliance with table 5.2a of ADF1- as detailed below. 

System 2: Passive stack ventilation in compliance with table 5.2b of ADF1. 

System 3: Continuous mechanical extract in compliance with table 5.2c of ADF1. 

System 4: Continuous mechanical supply and mechanical extract with in heat recovery 

compliance with table 5.2d of ADF1. 

System 1: Purge (natural) ventilation with background ventilation & 

intermittent extract fans 

Purge (natural) ventilation to habitable rooms 

Purge (natural) ventilation to be provided to all habitable rooms equal to 1/20 th (5%) floor 

area where the external windows/doors open more than 30 degrees and increased to 

1/10 th (10%) of the floor area where the windows opens between 15 - 30 degrees. 

Window openings which open less than 15 degrees is not suitable for purge ventilation 

and alternative ventilation details are required as detailed below and in compliance 

section 5 & Appendix B of Approved Document F1. Purge (natural) ventilation openings 

to habitable rooms to be typically 1.75m above floor level. 

Mechanical extract ventilation & fresh air inlets for rooms without purge ventilation 

Mechanical extract ventilation & fresh air inlet are required for habitable rooms without 

purge (natural) ventilation which must designed by a ventilation specialist having 

a minimum of 4 air changes per hour & manually controlled in compliance section 5 of 

Approved Document F1. 

Purge ventilation to wet rooms (kitchens/utility/bath/wc/en suit etc) 

Opening windows are required for purge (natural) ventilation to wet rooms (kitchens/ 

utility/bath/wc/en suit etc) which have external walls (no minimum sizes) in compliance 

section 5 of ADF1. 

General requirements for purge (natural) ventilation 

Purge (natural) ventilation openings to habitable rooms to be typically 1.75m above floor 

level and all internal doors to have a 10mm gap under the door for air supply transfer. 

The area of external windows, roof windows & doors should not exceed 25% of the 

usable internal floor area otherwise SAP calculations may be required from a suitably 

qualified person to confirm design flexibility where they exceed 25% of the usable floor 

area. (ii) See the relevant section in this guidance for permitted unprotected external 

openings in relation to relevant boundaries. 

Means of escape windows to be fitted with proprietary hinges to open to the minimum 

required clear width of 450mm. Escape windows must have minimum clear opening 

casement dimensions of 0.33m² and 450mm (typically 450mm wide x 750mm high), 

located within 800-1100mm above floor level to all bedrooms and habitable rooms at 1st 

floor level and inner habitable rooms on the ground floor. Windows above the ground 

floor storey and within 800mm of floor level are to be provided with containment/ 

guarding/ proprietary catches which should be removable (child proof) in the event of a 

fire. Where escape windows cannot be achieved, direct access to a protected stairs (or 

protected route to inner rooms) is acceptable in compliance with ADB1- par 2.6 (a) or (b). 

40

Mechanical extract ventilation to new dwellings 

Mechanical extract ventilation rates 

Mechanical ventilation is to be provided to the rooms listed below directly ducted to the 

outside air equivalent to the following rates. 

Kitchen 30 litres per second over hob or 60 litres elsewhere 

Utility room 30 litres per second 

Bathroom 15 litres per second (including shower rooms & en-suites) 

Toilet 6 litres per second W/C (with or without a window) 

Mechanical ventilation to rooms without open able windows to be linked to light operation 

and have 15 minutes overrun and a 10mm gap under the door for air supply. 

Note: Fans must not be installed in rooms containing open flue appliances unless the 

Interaction of mechanical ventilation & open flue heating appliances is checked and 

certified by an approved method & suitably qualified person as contained in ADJ. 

Continuous mechanical extract 

Continuous mechanical extract ventilation details are required in compliance with tables 

5.1a & 5.1b of ADF1. 

Whole building mechanical extract 

Whole building mechanical extract ventilation details are required in compliance with 

table 5.1b of ADF1. 

General requirements for mechanical extract ventilation 

Mechanical ventilation to rooms without open able windows to be linked to light operation 

and have 15 minutes overrun and a 10mm gap under the door for air supply. 

Fans must not be installed in rooms containing open flue appliances unless the 

interaction of mechanical ventilation & open flue heating appliances is checked and 

certified by an approved method & suitably qualified person as contained in ADJ. 

Mechanical ventilation to be ducted in proprietary insulated ducts to outside through 

walls to proprietary vent or through roof space to proprietary matching tile /soffit vent 

Background ventilation to new dwellings 

Background ventilation to be provided to all rooms with external walls either through 

walls or in windows via hit and miss or 2 stage window catches equivalent to 

5000mm 2 minimum to each habitable room and 2500mm 2 minimum to each wet 

room (kitchens/utility/bath/wc/en suit etc). 

The total area of background ventilation must be in compliance with Table 5.2a of ADF1 

as follows: 

(i) For dwellings with any design air permeability use Table A below 

(i) For dwellings with design air permeability worse than 5m 3 /(h.m 2 ) use Table B below 

Background ventilation to be located typically 1.75m above floor level. 

Note: For buildings with no external walls use appropriate ventilation system 2,3 or 4 in 

compliance with paragraphs 5.8- 5.10 of ADF1. 

41

Table A:Total background ventilation (mm 2 ) required for new dwellings with any 

design air permeability 

Number of bedrooms 

Total floor area (m 2 ) 1 2 3 4 5 

Less 50 35000 40000 50000 60000 65000 

51-60 35000 40000 50000 60000 65000 

61-70 45000 45000 50000 60000 65000 

71-80 50000 50000 50000 60000 65000 

81-90 55000 60000 60000 60000 65000 

91-100 65000 65000 65000 65000 65000 

100+ Add 7000mm 2 for every additional 10m 2 floor area 

Table B:Total background ventilation (mm 2 ) required for new dwellings with design 

air permeability leaker than 5m 3 /(h.m 2 ) 

Number of bedrooms 

Total floor area (m 2 ) 1 2 3 4 5 

Less 50 25000 35000 45000 45000 55000 

51-60 25000 30000 40000 45000 55000 

61-70 30000 30000 30000 45000 55000 

71-80 35000 35000 35000 45000 55000 

81-90 40000 40000 40000 45000 55000 

91-100 45000 45000 45000 45000 55000 

100+ Add 5000mm 2 for every additional 10m 2 floor area 

42

Part G: Sanitation, hot water safety and water efficiency 

Sinks with hot and cold running water is to be provided in all food preparation areas, 

bathrooms to be fitted with either a bath or shower. Hot & cold water taps to wash basins, 

baths, showers & sinks including external taps to have water from a wholesome water 

supply. Outlets from domestic hot water storage vessels to be fitted with an in line hot 

water supply tempering valve to prevent water temperatures exceeding 60 ºC. 

Softened wholesome cold water should not be provided where drinking water is 

drawn off or to any sink where food is prepared 

The estimated water consumption for new dwellings and flats (including changes of use) 

is to be calculated using a ‘Water Efficiency Calculator’ which is to be submitted at the 

application stage and approved by building control before works commence on site. 

The estimated consumption of wholesome water should not exceed 125 litres per 

person/ per day including a fixed factor of water for outdoor use of 5 litres per person/ per 

day. 

Typical specification for flow rates: 

4/2.6 dual flushing toilets 

All taps fitted with flow regulators to 4 litres per minute 

Shower with flow rates of 6-9 litres per minute 

Standard bath (140 litres capacity to over flow) 

Standard washing machine 

Standard dishwasher 

Baths to be fitted with an in line mixing valve to restrict the temperature to 48 degrees C 

max 

Hot water storage systems to be restricted to 100 degrees C max and outlets from 

domestic hot water storage vessels to be fitted with an in line hot water supply tempering 

valve to prevent water temperatures exceeding 60 degrees C max. 

Hot water storage vessels to be fitted with a non-self-setting energy cut out to instantly 

disconnect the power supply. 

Wash hand basins to be provided in all rooms containing a w/c and a door must separate 

the w/c from any food preparation area in a dwelling 

Water tanks/cisterns must have an adequate designed flat platform base to support the 

proposed loads. 

Pumped small bore foul water drainage from a toilet is only permitted if there is also 

access to a gravity draining toilet in the same dwelling. Proprietary pumped foul water 

macerator systems must have BBA or other approved accreditation and fitted in 

compliance with manufacturers details to a suitable foul water drainage system. 

Commissioning certificates for fixed building services are required on completion with 

copy sent to building control 

43

Part H: Drainage and waste disposal 

H1: Foul water drainage 

New Foul water connections to the public sewer 

Owners of new dwellings are required to consult with the Water Authority and obtain 

consent for new foul (& where necessary) surface water connections to the public sewer 

before works commence site. 

Foul, rain & storm water drainage systems 

Both storm and foul drainage to consist of 100mm diameter UPVC proprietary 

underground drainage laid at a minimum gradient of 1:40 where serves up to one wc or 

1:80 where serves two or more wc’s, surrounded in pea/single size gravel a minimum of 

900mm deep in drives and roads and 400mm elsewhere, unless provided with a 100mm 

reinforced concrete slab with compressible material under and 300mm min bearing on 

original ground. 

Proprietary UPVC 450mm diameter inspection chambers to be provided at all changes of 

level and or direction and at 45m maximum spacing in straight runs up to 1.2m in depth. 

All gullies to be trapped and have rodding access where serving branches. Inspection 

chamber covers to be mechanically fixed and suitable for vehicular loads in drives and 

roads and proprietary bolt down double sealed covers and frames in buildings. 

Foul water to be discharged to new or existing facilities as shown on plans/specification 

and storm water from individual down pipes to be piped 5m away from buildings and to 

be disposed in a separate surface water sewer via trapped gullies or to soakaways 

minimum 2m³ clean filled rubble soakaways per rain water pipe serving a roof area upto 

30m2, covered with polythene and top soil or to other methods as shown on the 

drawing/specification. Soakaways in clay sub soils or serving roof areas exceeding 30m2 

per rwp to be designed in accordance with BRE Digest 365 or by a specialist (i.e. 

Hydrologist). Rain/surface water systems cannot be connected to foul water drains 

without the written permission of the relevant Water Authority. 

Foul drainage systems to low lying buildings or basements which carry storm water or 

other vulnerable drainage systems should be provided with anti flood protection such as 

one way valves, etc, to prevent flooding and sewerage entering the building. 

Waste pipes 

All W/Cs to have trapped outlet connected to 100mm diameter pipes, and to be provided, 

with a wash hand basin with hot and cold running water. Sanitary appliances such as 

wash hand basin, baths, showers, sinks etc, to be provided with 50mm diameter waste 

pipes laid to falls and 75mm deep seal traps. Where waste pipe runs exceed 4m BBA 

approved air admittance valves are to be fitted above appliance spill over level. Waste 

pipes to either discharge below trapped gully grating or into soil and vent pipes via 

proprietary waste manifolds or bossed junctions. Internally all waste and drainage pipes 

to have rodding access/eyes at changes of direction and be adequately 

clipped/supported and provided with 30 minutes fire protection where passing through 

floors. 

44

H2: Septic tanks, sewage treatment systems & cesspools 

Existing septic tank & effluent drainage 

Where additional drainage effluent is to be connected to the existing septic 

tank/treatment system, it should be checked by specialist and sizes/condition of 

tank/system to be confirmed suitable for treatment of additional effluent. 

Non mains foul drainage waste water treatment systems 

Non mains drainage systems are to be used only where connection to the mains 

drainage system is not possible. Either septic tank or sewage treatment system to be 

installed as agreed with Building Control to suit specific ground conditions. No septic 

tank/ sewage treatment system and associated secondary treatment is permitted by the 

Environment Agency in prescribed Zone 1 ground water source protection zones. Where 

no other option is feasible, the installation of a cesspool is to be agreed with Building 

Control & the Environment Agency. 

Septic tanks 

Septic tanks to consist of a watertight chamber, water proof from both sides and the 

sewage is liquefied by anaerobic bacterial action in the absence of oxygen assisted by 

the natural formation of a surface scum or crust. Sludge settlement at the base of the 

tank must be removed annually. Discharge from tanks to be taken to drainage fields, 

drainage mounds or wetlands/reed beds for secondary treatment as detailed below. 

Proprietary factory made septic tanks to be designed and constructed to BS EN 12566 

and installed in compliance with manufacturer’s details, or 

Non proprietary septic tanks constructed in situ to be designed and constructed to a 

drainage specialist’s design, approved by Building Control before the works commence 

on site. Typically, the tank consists of two chambers constructed using 150mm minimum 

thick concrete base C25P mix to BS 5328, 220mm thick engineering quality brickwork 

walls (or concrete), mortar mix 1:3 cement/sand ratio with designed heavy concrete roof 

slabs. 100mm diameter Inlet and outlet ‘dip pipes’ designed to prevent disturbance of the 

surface scum, inlet pipe laid at a flatter gradient for at least 12 meters before it enters the 

tank. 

Septic tanks to be fitted with durable lockable lids or covers for emptying and cleaning, 

and inspection chamber fitted on the discharge side of tank for sampling of the effluent. 

Septic tanks to be sited 7m from any habitable part of any building and preferably 

down slopes and have a minimum capacity of 2,700 litres for upto 4 users & increased 

by 180 litres for each additional user. (Recommended size of septic tank to be 

3,800 litres minimum). 

A notice plate must be fixed within the building and include the following information: 

Address of the property; location of the treatment system; description of the septic tank 

and effluent drainage installed; necessary maintenance to be carried out (including 

monthly checks of the apparatus and emptying of the tank every 12 months by a licensed 

contractor) and a statement that the owner is legally responsible to ensure that the 

system does not cause pollution, health hazard or nuisance. 

Consultations are to be carried out with Building Control and The Environment Agency 

before any works commence on site. It is the Occupiers responsibility to register the 

effluent discharge as an exempt facility with the Environment Agency for discharges of 

2m3 or less per day to the ground from a septic tank. 

45

Sewage treatment systems 

Proprietary sewage treatment systems treat sewage by an accelerated process to 

higher standards than that of septic tanks, and are to be factory made, designed and 

constructed to BS EN 12566 (if less than 50 persons otherwise to BS 6297: 1983 Code 

of Practice for design and installations of small sewage treatment works and cesspools 

and BBA certification or other approved accreditation), installed and maintained in 

compliance with the manufactures details and fitted with a uninterruptible power supply 

(or 6 hours power back up). Note: only treatment systems suitable for intermittent use 

should be used for holiday lets or similar where the system is unused for periods of time. 

Sewage treatment system to be sited 7m from any habitable part of any building and 

preferably down slopes and have a minimum capacity of 2,700 litres for upto 4 users & 

increased by 180 litres for each additional user. 

Discharges from sewage treatment systems can be taken to a water course or 

alternatively a designed drainage field, drainage mound, wetlands or reed beds as 

detailed below. 


Address of the property; location of the treatment system; description of the sewage 

treatment system and effluent drainage installed; necessary maintenance to be carried 

out in accordance with the manufacturers details and a statement that the owner is 

legally responsible to ensure that the system does not cause pollution, health hazard or 

nuisance. 

Consultations should be carried out with Building Control and The Environment Agency 

before any works commence on site. It is the Occupiers responsibility to register the 

effluent discharge as an exempt facility with the Environment Agency for discharges of 

5m 3 or less per day to a surface water course or 2m 3 or less per day to the ground from 

a sewage treatment system. 

Treatment of sewage from septic tanks & sewage treatment systems 

Drainage fields 

Drainage fields to consist of irrigation pipes constructed below ground allowing partially 

treated effluent to percolate into the ground and further biological treatment in the 

aerated soil layers. 

Construction of drainage fields to be carried out as tank/system manufacturers details 

and BS 6297:2007 + A1:2008. See typical section detail and drainage field layout below. 

The drainage field area is calculated from the percolation test results which should have 

a suggested minimum area of 30m x 0.6m wide subject to percolation test results and 

number of users and approved by Building Control before works commence on site. See 

below for percolation test procedure. 

Drainage fields to be located 10m from any water course, 50m from any point of water 

abstraction, 15m from any building & sufficiently far from any other drainage areas so the 

overall soakage capacity of the ground is not exceeded. Water supply pipes, access 

roads, drives or paved areas etc must not be located within the drainage areas. 

Drainage mounds 

Drainage mounds to consist of drainage fields constructed above the ground allowing 

further biological treatment of the partially treated effluent in the aerated soil layers. 

Drainage mounds to be used where there is a high water table level, impervious or semi 

46

water logged ground. Drainage mounds and drainage mound areas should be designed 

by a drainage specialist for particular ground problems and approved by Building Control 

before works commence on site. See diagram 2 of ADH for typical drainage mound 

construction details. 

Drainage mounds to be located 10m from any water course, 50m from any point of water 

abstraction, 15m from any building & sufficiently far from any other drainage areas so the 

overall soakage capacity of the ground is not exceeded. Water supply pipes, access 

roads, drives or paved areas etc must not be located within the drainage areas. 

Wetlands/reed beds 

In situations where drainage fields or mounds are not suitable, wetland treatment 

systems consisting of manmade reed beds can be constructed as either vertical or 

horizontal flow reed bed systems for the purification of the partially treated effluent by 

filtration, biological oxidization, sedimentation and chemical precipitation as the partially 

treated effluent passes through gravel beds and root systems of wetland plants. 

Wetlands should not be constructed in shaded or severe winter areas. 

Vertical or horizontal flow wetland treatment systems should be designed by a drainage 

specialist for particular ground problems and approved by Building Control before works 

commence on site. 


Address of the property; location of the treatment system; description of the sewage 

treatment system and effluent drainage installed; necessary maintenance to be carried 

out in accordance with the drainage specialists details and a statement that the owner is 

legally responsible to ensure that the system does not cause pollution, health hazard or 

nuisance. See diagram 3 of ADH for typical horizontal flow reed bed system and 

diagram 4 of ADH for typical vertical flow reed bed system. 

Percolation test method to calculate area of drainage field for septic tanks 

or sewage treatment systems. 

Step 1: Excavate a test hole 300mm square x 300mm deep below proposed invert level 

of the drainage field trench bottom 

Step 2: Fill the test hole with water and allow drain away over night 

Step 3: Refill to a depth of 300mm and note time taken in seconds to drain away 

from 75% full to 25% full (i.e. 150mm drop in level from 225mm to 75mm) 

Step 4: Repeat the procedure in two more test holes and calculate the average of the 

three results as follows: test 1 + test 2+ test 3 = average time taken 

3 

Step 5: Calculate the Vp (average time in seconds for the water to drop 1mm) as follows: 

For example: If average time above took 2100 seconds 

(i) Divide 2100 seconds by 150mm depth of water 

(ii) 2100 = 14 Vp* (see note below*) 

150 

(iii) Area of trench = number of persons to use property X Vp X 0.25 

Therefore: 5 persons X 14 X 0.25 = 17.5m 2 of effluent drain required. 

(iv) To calculate actual length of trench divide 17.5m 2 by width of the trench required 

therefore: 17.5m 2 = 29.16 (Minimum permitted area is 30m long x 0.6m wide) 

0.6m wide 

* Vp should range between 12 and 100 to be successful; otherwise the system should be 

designed by a drainage specialist. 

47

Diagram 14: Typical section through a septic tank/sewage treatment system 

drainage field (not to scale) 

Diagram 14.1 : Typical drainage field plan layout (not to scale) 

Inlet 

Cross section detail of a septic tank/sewage treatment 

effluent drainage soakaway trench (not to scale) 

Ground level 

Back fill with excavated 

material 

1200g polythene layer 

100mm diam ridgid Upvc 

slotted pipe (slots laid 

down), laid at 1:200 

25-50mm diam clean 

stone below & covering 

pipe 

Winter water table level 

Distribution/sampling 

chamber 

2000mm 

min non 

slotted 

upvc pipe 

Septic tank/sewage treatment 

plant as guidance details 

600 to 900mm 

wide trench, as 

drainage field 

layout belowminimum 

30m 

length of pipe work 

600mm wide trench as 

guidance details 

2000mm min separation 

50mm 

100mm diam pipe 

150mm 

2000mm min separation 

At least 1.0m 

from winter 

water table 

level 

100mm diam perforated 

effluent distribution pipes 

(perforations laid down) 

30m minimum length of 

rigid upvc pipes 

Note: All effluent drainage pipe work from the tank to be laid at 1:200 gradients etc as guidance details 

Minimum 

depth 500mm 

48

H3: Rainwater drainage and harvesting 

Rainwater gutters and down pipes 

Rainwater gutters and down pipe sizes and number to be suitable for roof area to be 

drained in compliance with the table below, and fixed in compliance with manufactures 

details. See H3 of ADH for further information 

Table 20: Gutter sizes & pipe outlet sizes for drainage of roof areas 

Max effective roof area m2 Gutter sizes (mm 

diam) 

Outlet sizes (mm diam) 

18.0 

75 

50 

37.0 

100 

63 

53.0 

115 

63 

65.0 

125 

75 

103.0 

150 

89 

The sizes above refer to half round gutters & round rain water pipes 

Rainwater/ grey water harvesting storage tanks & systems 

Rainwater harvesting system to be designed, supplied, installed, and commissioned by 

specialist to supply rainwater to sanitary appliances. Below drainage pipework as foul 

water pipe guidance details above. 

Grey water systems designed for use within the building is to be designed, 

manufactured, installed and commissioned by a suitably qualified and experienced 

specialist. Grey water to be treated prior to use in toilets etc by an approved method. 

Overflow from the rain water storage tank is to discharge to a designed soakaway system 

constructed 5m from any building & septic tank soakaway system. 

Grey water & rainwater tanks & systems should: 

Prevent leakage of the contents, ingress of subsoil water & should be ventilated 

Have an anti backflow device on any overflow connected to a drain or sewer 

Have a corrosion proof locked access cover for emptying & cleaning 

Supply pipes from the grey water or rain water collector tanks to the dwelling must 

be clearly marked as either ‘GREY WATER’ or ‘RAIN WATER’. 

Guidance should be followed in par 1.69-1.72 of App Doc H2, App Doc G of the 

Building Regulations and the Water Regulations Advisory Scheme Leaflet No: 09- 

02-04, and BS 8515:2009. 

Surface water drainage around the building 

Paths and paved areas around the building to have a non slip finish and if not porous 

propriety design to be provided with a cross fall of 1:40 – 1:60 and a reverse gradient of 

at least 500mm away from walls of building. Surface water to be disposed of by an 

adequately sized and roddable drainage system via soakaways, or other approved 

means. 

49

Oil/fuel separators 

Under section 111 (restrictions on use of public sewers) of The Water Industries Act 

1991, it is an offence to discharge fuels into water courses, coastal water or underground 

water. Oil separators are required where fuel is stored or in other high risk areas or car 

parks and the Environment agency has issued guidance on the provision of oil 

separators. 

For paved areas around buildings or car parks a bypass separator is required with a 

nominal size (NSB) of 0.0018 times the contributing area and silt storage area (in litres) 

equal to 100 times the NSB. 

In fuel storage areas and other high risk areas full retention separators are required with 

a nominal size (NS) equal to 0.018 times the contributing area and silt storage area (in 

litres) equal to 100 times the NS. 

Separators discharging to infiltration devices or surface water sewers should be class 1 

Proprietary oil separators should be, factory made, water proof, designed and 

constructed to the requirements of the Environment Agency, licensing authorities 

requirements (where the Petroleum Act applies), prEN858 and BBA certification or other 

approved accreditation. Separators must be installed and maintained in compliance with 

the manufacturers details and inlet arrangements should not be direct to the water 

surface, and adequate ventilation must be provided. See Appendix H3 -A of ADH3 for 

further information 

H4: Building over or close to public sewers 

Owners of building being constructed, extended or underpinned within 3m of a public 

sewer as indicated on the relevant Water Authorities sewer maps are required to consult 

with the Water Authority and where necessary obtain consent and enter into an 

agreement to build close to or over the public sewer before works commence site. 

Protection of the sewer pipe and systems are to be carried out in compliance with the 

relevant Water Authorities requirements. 

As part of this process, building control will check the proposed development against the 

relevant Water Authorities sewer maps regarding building over/close to the public sewer 

and where necessary building control will consult with the Water Authority and request 

that they send any comments directly to the building owner/agent within 14 days of the 

consultation. Building notices are not acceptable where an agreement is required to 

building close to or over a public sewer and full plans applications will be required. See 

H4 of ADH for further information 

H5: Separate systems of drainage 

The building owner/agent must carry out all necessary consultations with the 

relevant Water Authority before works commence on site. Rain/surface water systems 

cannot be connected to foul water drains without the written permission of the relevant 

Water Authority. See H5 of ADH for further information. 

H6: Solid waste storage 

1200 X 1200mm level paved areas are required beside rear access for refuse storage 

containers or alternatively a communal storage area can be provided for a wheelie bin 

suitable to store 0.25m3 minimum per dwelling subject to approval from the waste 

collection authority. 

50

Part J: Combustion appliances & fuel storage systems 

Space & hot water heat producing appliances in general 

Space and hot water heating method as detailed on the plans/specification. Heating to be 

supplied from new or extended gas/LPG/oil fired wall/floor mounted condensing balanced 

flue boiler with the flue discharging 600mm minimum away from openings into the 

building and protected with a proprietary wire basket to boiler manufacturers 

specification. 

Boilers to have a SEDBUK efficiency above 90% to comply with Building Regulations as 

amended in October 2010 for gas/ LPG/oil and must be provided with separate controls 

for heating and hot water with a boiler interlock, timer, and thermostat radiator valves to 

each room. Un-vented hot water systems require safety devices including non self setting 

energy cut out & temperature release valve and thermostat. Safety valves from vented 

hot water systems must discharge safely. 

Hot water vessels to be insulated with 35mm minimum thickness of PU foam and both 

heating and water pipes to be insulated with proprietary foam covers equal to their 

outside diameter within 1m of the vessel and in unheated areas. Hot water storage must 

not exceed a temperature of 100 degrees centigrade. 

Gas installations to be installed and comply with BS 5440, BS 5546, BS 5864, BS5871, 

BS 6172, BS 6173 and BS 6798. 

Oil installations to be installed and comply with BS 5410, BS 799. 

All space and hot water systems must be installed, commissioned, calibrated and 

certified by a suitably qualified person or installer registered with an appropriate 

competent persons scheme and details supplied to Building Control and the owner along 

with the operating manuals, etc before the building is completed/occupied. 

Solid fuel appliances up to 50kW rated output 

Construction of open fire place with recess & hearth 

Fire place walls to consist of non combustible material of at least 200mm in thickness to 

the side 100mm thick in the back wall recess, lined with suitable fire bricks. The hearth to 

be at least 125mm thickness (or 12mm thick if provided over a concrete floor slab) of non 

combustible materials with projections at least 150mm to the sides of the side jambs and 

500mm in front of the jambs. 

Free standing stove with hearth 

Free standing stoves & hearths to be positioned 150mm minimum away from enclosing 

non combustible walls at least 100mm thick. Hearths to be at least 125mm thickness (or 

12mm thick if provided over a 100mm thick concrete floor slab),constructed of non 

combustible materials with projections at least 150mm to the sides & rear of the 

appliance and 300mm in front of the appliance door. 

Air supply (ventilation) to solid fuel appliances 

Permanently open combustion air vents ducted to outside are to be provided in the same 

room as the solid fuel appliance with a total free area in compliance with the table below 

(see Table 1 of ADJ for further information) 

51

Table 21: Air supply (ventilation) to solid fuel appliances 

Type of appliance Amount of ventilation 

Open fire place with no throat (i.e. under a 50% of the cross section area of the 

Canopy) 

Flue 

Open fire place with throat 

or for simple fire openings: 

500mm wide 

450mm wide 

400mm wide 

350mm wide 

Enclosed stove with flue draught stabilizer 

In new dwellings 

Enclosed stove with no flue draught 

stabilizer In new dwellings 

50% of the cross section area of the 

Throat opening area 

20,500mm 2 

18,500mm 2 

16,500mm 2 

14,500mm 2 

850mm 2 /kW of appliance rated out put 

550mm 2 /kW of appliance rated out put 

Carbon monoxide alarms 

Mains operated carbon monoxide alarm is required at ceiling level in the same 

room as the solid fuel appliance, which must be either battery operated in 

compliance with BS EN 5029: 2001: or mains operated with sensor failure 

warning device in compliance with BS EN 5029: Type A 

Carbon monoxide alarm to be positioned on the ceiling at least 300mm from 

walls, or if located on the wall as high up as possible (above any doors or 

windows) but not within 150mm of the ceiling, and between 1m and 3m 

horizontally from the appliance 

Table 22: Sizes of flues in chimneys 

Installation Minimum internal flue sizes 

Fire place with opening up to 500 x 500mm 200mm (diameter, rectangular or square) 

Fire place with opening more than 500 x 

500mm or exposed on both sides 

Closed appliances* (stove, cooker, room 

heater & boiler) up to 30kW rated output 

30- 50kW rated output 

Closed appliances up to 20kW rated output 

which-burns smokeless/low-volatile fuel, or 

complies to the Clean Air Act 

Pellet burner which compiles to the Clean 

Air Act 

Area equal to 15% of the total face area of 

the fireplace opening. (note: total face 

areas more than 15% or 0.12m 2 to be 

designed by heating specialist) 

(diameter, rectangular or square) 

150mm 

175mm 

See table 2 of ADJ 

See table 2 of ADJ 

52

Construction of masonry chimneys 

Chimneys to be constructed in external quality frost resistant materials 100mm minimum 

thickness (increased to 200mm where separates another fire compartment or another 

dwelling), using brick, dense blocks or reconstituted/natural stone to match the existing, 

with suitable mortar joints for the masonry as the masonry manufacturers details with any 

combustible material kept at least 50mm away from the walls containing flues. 

Line chimney with manufactured flue liners installed in compliance with manufacturers 

details as follows: 

(i) Clay flue liners to BS EN 1457:2009: Class A1 N1 or Class A1 N2, to be laid vertically 

and continuously socket up (jointed with fire proof mortar) from appliance with a 

minimum diameter in compliance with table 22 

(ii) Concrete flue liners to BS EN 1857:2003: Type A1, A2, B1 or B2 to be laid vertically 

and continuously socket up (jointed with fire proof mortar) from appliance with a 

minimum diameter in compliance with table 22 

(iii) Liners whose performance complies to BS EN 1443:2003: designation: T400 N2 D 3 

G with a minimum diameter in compliance with table 22 

Backfill gaps between masonry and flue liners with a weak mix concrete using 1:6 

ordinary Portland cement and vermiculite. Build in code 5 lead flashings (including apron 

& lay board flashings) & dpc tray into chimney as work proceeds, 150mm above all 

roof/wall abutments as necessary & terminate chimney with a proprietary chimney pot to 

match the internal flue sizes. 

Construction of factory made flue block chimneys 

Construction of factory made flue block chimneys are to be carried out in compliance with 

paragraphs 1.29 – 1.30 of ADJ, and appliance manufacturer’s details. 

Construction of factory made metal chimneys 

Construction of factory made metal chimneys are to be carried out in compliance with 

paragraphs 1.42 – 1.46 of ADJ, and appliance manufacturer’s details. Factory made 

metal chimneys are to be concealed in the building in compliance with paragraph 1.47 & 

diagrams 13 & 14 of ADJ. 

Configuration of flues serving open flue appliances 

Flues to be constructed straight and vertical with no more than a 90 degree bend with 

cleaning access where the flue connects to the appliance and no more than two 45 

degree bends (to the vertical) in the flue configuration in compliance with paragraph 

1.48- 1.49 of ADJ, . 

Inspection & cleaning openings in flues 

Inspection & cleaning openings should be air tight using proprietary factory made 

components compatible with the flue system, fitted & located to allow sweeping of the 

flue in compliance with appliance manufacturers details 

Interaction of mechanical extract vents & opened flue solid fuel appliances 

Where a kitchen contains an opened flue- solid fuel appliance, confirm extract 

ventilation will not be installed in the same room as the appliance, or alternatively seek 

further guidance from HETAS. 

53

Chimney heights 

Chimney height not to exceed 4.5 times its narrowest thickness. Chimney/terminal to 

discharge at a minimum height of: 

1.0m above flat roofs 

1.0m above opening windows or roof lights in the roof surface 

0.6m above the ridge 

Outside of a zone measured 2.3m horizontally from the roof slope 

0.6m above an adjoining or adjacent building that is within 2.3m measured 

horizontally (whether or not beyond the boundary) 

Please refer to Diagram 17 of ADJ for full details 

Alternative heating producing appliances as detailed on the drawing/specification to be in 

compliance with ADJ. 

Repair/relining of existing flues 

Repair /relining of existing flues to be carried out by a suitably qualified and experienced 

specialist. Re-use of existing flues to be inspected, tested and certified by a suitably 

qualified and experienced specialist prior to use as suitable for solid fuel appliances. 

Relining of existing flues to be carried out in compliance with BS EN 1443:2003: 

designation: T400 N2 D 3 G with minimum diameters in compliance with table 22 using 

lining systems suitable for solid fuel appliances as follows: 

(i) Factory made flue lining systems in compliance with BS EN 1856-1:2003 or BS EN 

1856-2:2004 

(ii) Cast in-situ flue lining system in compliance with BS EN 1857:2003+A1:2008 

Notice plates for hearths & flues 

Notice plates for hearths & flues should be permanently displayed next to the flue (or 

electricity consumer unit or water stop tap) detailing the property address; location of 

installation (room); type of installation the flue is suitable for; size & construction of flue, if 

suitable for condensing appliance, installation date, and any other information (optional). 

Appliances other than solid fuel 

Interaction of mechanical extract vents & opened flue combustion appliances 

Gas appliances 

Where a kitchen contains an opened flue- gas appliance, the extract rate of the kitchen fan 

should not exceed 20 l/s (72m3/hour) and the appliance should be tested and certificated by a 

suitably qualified and registered gas engineer that the combustion appliance operates safely 

whether or not the fans are running. 

Oil appliances 

Where a room contains an opened flue- oil appliance, the extract rate of the fan should not 

exceed 40 l/s for an appliance with a pressure jet burner and 20l/s for an appliance with a 

vaporising burner. 

Gas heating appliances up to 70kw 

Gas burning appliances up to 70kW to be installed, commissioned and tested in 

compliance with section 3 of ADJ, and the Gas Safety (installation & use) Regulations. 

All works to be to be carried out by an installer registered with Gas Safe. Copy of 

commissioning certificates to be issued to Building Control on completion of the works. 

54

Oil heating appliances up to 45kW 

Oil burning appliances up to 45kW to be installed, commissioned and tested in 

compliance with section 4 of ADJ. All works to be to be carried out by an installer 

registered with OFTEC. Copy of commissioning certificates to be issued to Building 

Control on completion of the works. 

Renewable energy Installations 

Renewable energy systems must be installed, commissioned, calibrated and certified by 

a suitably qualified person or specialist installer registered with an appropriate competent 

persons scheme (where applicable) and details supplied to Building Control and the 

Owner along with the operating manuals, etc for the following installations: 

Solar photovoltaic (pv) roof/wall panels for producing electricity 

Biomass space heating & hot water systems 

Wind energy turbines for producing electricity 

Hydro-power systems for producing electricity 

Solar water heating roof/wall panel systems, fitted with an additional heating 

source to maintain an adequate water temperature 

Ground/air source heat pumps for space heating & hot water systems 

All roof / wall structures must be adequate to support the above installations in 

compliance with manufacturers details or calculations & details from a suitably qualified 

person which must be approved by Building Control before works commence on site. 

Provision of information- commissioning certificates (testing) 

Copy of installers commissioning certificate to be sent to building control on completion 

of the work. 

Fuel storage tanks 

LPG tanks and cylinders up to 1.1 tonnes 

LPG tanks and cylinders up to 1.1 tonnes to be positioned in the open air at least 3m 

from buildings or boundaries. LPG cylinders to be positioned in the open air on a 

minimum 50mm thick concrete base, securely chained to the wall and positioned at least 

250mm below and 1m from any openings horizontally into the building such as windows, 

combustion, vents or flue terminals and 2m from un-trapped drains or cellar entrances. 

Oil tanks up to 3500 litres 

Oil tanks up to 3500 litres to be positioned in the open air on a concrete base with a 

minimum thickness of 50mm extending a minimum of 300mm beyond the tank base and 

be positioned a minimum of 1.8m from buildings or flues and 760mm from boundaries. 

They should also be provided with a proprietary fire resistant pipe and valve system. 

Where there is a risk of pollution to water courses, open drains including inspection 

chambers with loose covers, the tank should be either internally bunded or be provided 

with an impervious masonry bund equal to capacity of 110% of its volume. Where any of 

the above requirements cannot be met- please contact building control for further 

guidance. 

55

Part K: Protection from falling, collision and impact 

Internal stairs, landings and changes in level of 600mm or more 

Stairs to be constructed (and finished) in materials to Clients choice to BS 5395 & 

BS 585 as detailed below:- (Spiral & helical stairs to be designed to BS 5395: Part 2) 

Stair pitch not to exceed 42° and design to be based upon dimensions taken from site 

and drawing. 

Rise and going to be level and equal to all steps and to fall within the following separate 

classes:- 

Any rise between 155mm-220mm used with any going between 245mm- 260mm, 

or 

Any rise between 165mm-200mm used with any going between 223mm- 300mm. 

(Twice the rise plus the going must be between 550 & 700mm) 

Diagram 15: Measuring rise & goings (not to scale) 

open riser 

Note: treads 

should over lap at 

least 16mm 

tread 

riser 

Note: going dimention to 

be measured from nosing 

to nosing 

nosing 

going 

top surface of tread 

top surface of tread 

Stair to have a minimum headroom of 2000mm above stair pitch line and to be provided 

with landings clear of any door swing top and bottom equal in length to the width of the 

stairs. If doors open across a bottom of a landing- a clear 400mm space must be 

maintained across the width of the flight. Minimum stair width for new dwellings is 

900mm in the entrance storey suitable for disabled persons. 

Handrails must be provided on both sides of the stairs, at a height 900-1000mm above 

floor/nosing levels and continuous throughout their length suitable for disabled persons. 

All guarding is to be at a minimum height 900mm above floor/nosing levels and 

continuous throughout their length, with non climbable vertical balustrading, no gaps to 

exceeding 100mm and all constructed to resist a horizontal force of 0.36kn/m. All open 

treads, gaps etc should not exceed 100mm. 

Typical staircase construction details: side strings ex. 230 X 35mm, capping ex. 32 X 

63mm, treads 25mm thick, risers in 12.5mm thick plywood, newel posts ex. 75 X 75mm, 

handrails ex. 75 X 63mm, balustrades ex. 32 X 32mm at 125mm ctrs fixed into 

proprietary timber head & base rebated capping. 

rise 

` 

56

Diagram 16: Typical internal stair case & guarding construction details 

(not to scale) 

At least 2000mm clear head 

room (can be reduced to 

1900mm at the centre of the 

stairs & 1800mm at the side in 

loft conversions) 

Handrail & guarding 

at least 900mm high 

above landing level 

trimmer joists 

Landing 

Landings must 

be level & 

equal in 

length to the 

smallest width 

Note: No opening to 

allow the passage of 

100mm diam sphere 

Newel 

post 

Handrail & guarding 

at least 900mm high 

above pitch line 

tread 

External stairs, landings and changes in level of 600mm or more 

External stairs & landings 

As internal stair guidance details above 

non climable balustrades 

& no gaps to exceed 

100mm 

rise 

All guarding must 

resist a horizontal 

force of 

0.36kn/m 

outer string 

pitch line 

Max 

42 degree 

pitch 

At least 2000mm clear 

head room (can be 

reduced to 1900mm at the 

centre of the stairs & 

1800mm at the side in loft 

conversions) 

Flight Landing 

Note: Landings to be clear of any 

obstructions. A door may swing accross a 

landing at the bottom of a flight but must 

allow a 400mm min clear space accross the 

full width of the flight clear of any door 

swing 

External guarding 

Guarding to external stepped access/openings/balconies to be at least 1100mm high 

provided with non climbable vertical balustrading, with no gaps exceeding 100mm and 

constructed to resist a horizontal force of 0.74kn/m. All open treads, gaps etc should not 

exceed100mm. 

Guarding to upper storey window openings/other openings within 800mm of floor 

level 

Opening windows located above the ground floor storey with openings within 800mm of 

floor level must be provided with non climbable containment/guarding or proprietary 

catches which should all be removable (but child proof) to means of escape windows in 

the event of a fire. All gaps etc to containment/guarding should not exceed 100mm. 

57

Part L: Conservation of fuel and power in new dwellings 

Target & dwelling emissions rates 

Target Emissions Rate (TER) and a design Dwelling Emissions Rate (DER) to be 

provided in compliance with SAP 2009 and ADL1A as soon as possible and before 

works commence on site. 

Sap rating & energy performance certificate 

As built SAP rating (or design SAP rating if the construction details are unchanged) 

& registered energy performance certificate to be provided in compliance with SAP 

2009 and ADL1A, within 5 days prior to completion. 

Building control can provide a target and dwelling emission rate, SAP rating & 

registered energy performance certificate in compliance with SAP 2009 if required, 

please contact Building Control on 01594 810000 for more information. 

Fabric standards (worst acceptable standards) 

Thermal insulation standards in new dwelling to be in compliance with paragraphs 

4.18 - 4.24 and worst acceptable standards in compliance with table 2 of AD L1A as 

follows: 

Roof: U-value 0.20 W/m 2 .K 

Walls: U-value 0.30 W/m 2 .K 

Floor: U-value 0.25 W/m 2 .K 

Party wall: U-value 0.20 W/m 2 .K 

Windows, roof lights, 

doors & curtain walling : U-value 2.00 W/m 2 .K 

Air permeability: 10.00 m 3 /h.m 2 at 50pa 

Recommended starting u values 

Thermal insulation standards have been indicated in this guidance to achieve the 

following starting point U values: 

All roof types: U-value 0.13 W/m 2 .K 

Walls: U-value 0.18 W/m 2 .K 

Floors: U-value 0.13 W/m 2 .K 

U values for party walls 

Party walls U values to be in compliance with table 3 of AD L1A as follows: 

Solid walls: U-value 0.0 W/m 2 .K 

Unfilled cavity with effective edge sealing: U-value 0.2 W/m 2 .K 

filled cavity with effective edge sealing: U-value 0.0 W/m 2 .K 

Note: Unfilled cavity with no effective edge sealing will not achieve the minimum 

required worst case U-value of 0.2 W/m 2 .K 

58

Energy efficient lighting 

Fixed internal & external energy efficient lighting systems to be provided in 

compliance with paragraph 4.13 of ADL1A as follows: 

Fixed internal lighting 

Fixed internal energy efficient lighting in new dwelling will be at least 75% of all 

the fixed low energy light fittings (fixed lights or lighting units) in the main dwelling 

spaces (excluding cupboards & storage areas), fitted with lamps which must have a 

luminous efficiency greater than 40 lumens per circuit-watt and a total output greater 

than 400 lamp lumens. (note: light fittings with less than 5 circuit-watts are excluded) 

Fixed external lighting 

Fixed external energy efficient lighting in new dwelling will consisting of either; 

(i) Lamp capacity not greater than 100 lamp-watts per light fitting and fitted with 

automatic movement detecting control devices (PIR) and automatic daylight cut-off 

sensors; or 

(ii) Lamp efficacy greater than 45 lumens per circuit-watt; and fitted with automatic 

daylight cut-off sensors and manual controls. 

Limiting the effects of solar heat gains in summer 

Details of measures taken to limit solar gains to be provided in energy assessment in 

compliance with paragraphs 4.25-4.27 of ADL1 

Limiting thermal bridging around external openings 

Thermal bridging around external openings will be provided in compliance with 

paragraphs 5.9- 5.13 of ADL1A as follows: 

(i) Adopt a quality- assured accredited construction detail approach 

approved by the Secretary of State and the calculated linear thermal 

transmittance can be used directly in the DER calculation in compliance with 

paragraph 5.12 a. 

(ii) Use non- assessed details in compliance with BRE Report BR 497 

Conventions for Calculating Linear Thermal Transmittance and Temperature 

Factors 2007, (ISB N 978 1 86081 986 5) and the increased calculated values can 

be used in the DER calculations, in compliance with paragraph 5.12 b. 

(iii) Use unaccredited details with no specific quantification of the thermal bridge 

values. In such cases a conservative default y- value of 0.15 must be used in the 

DER calculation in compliance with paragraph 5.12 c. 

Air permeability & pressure testing 

Limiting air leakage 

Air leakage will be limited in the new dwelling fabric as indicated on plan layouts/ 

section details in compliance ADL1A and Accredited Construction Details (see 

information available from: www.planningportal.gov.uk) 

All external door and window frames, service penetrations to walls, floors, joists and 

ceilings, etc, should be sealed both internally and externally with proprietary sealing 

products such as proprietary waterproof mastic, expanding foam or mineral wool or tape 

to ensure air tightness. 

59

Pressure testing of new dwellings 

Where required by the SAP rating, pressure testing will be carried out by a specialist 

registered by the British Institute of Non-destructive Testing in compliance with the 

TER design limits in compliance with paragraphs 5.14- 5.22. Test results to be 

provided by specialist and copy sent to Building Control within 7 days after test 

carried out. 

Building control can provide pressure testing if required, please contact Building 

Control on 01594 810000 for more information. 

Pressure testing will be carried out on three units of each dwelling type or 50% of 

all instances of that dwelling type, whichever is the less in compliance with 

paragraph 5.18 of ADL1A. 

Alternative to pressure testing 

Alternative to pressure testing on small sites of less than two dwellings to be erected: 

(i) Confirm with test results that a same dwelling type has been constructed by the 

same developer within the last 12 months and has achieved the required design 

air permeability in compliance with paragraph 5.14- 5.18 of ADL1A. 

or 

(ii) To avoid the need for any pressure testing by using a value of 15m 3 /(h.m 2 ) at 

50Pa for the air permeability when calculating the DER. 

Providing information 

The following information will be provided in the new dwelling on completion in 

compliance with paragraphs 6.1- 6.4 of ADL1A: 

Operating & maintenance instructions for fixed building services 

Instructions how to make adjustments to timing and temperature 

control settings etc 

Instructions on routine maintenance requirements for fixed building services 

in compliance with manufacturers details 

Energy assessment data used to calculate the TER & DER and the as built 

Energy Performance Certificate 

60

Part M: Access to and use of buildings for disabled 

External ramped approach 

A level/ramped approach with a firm hard non slip surface at least 900mm wide is to be 

provided from a vehicular parking area or the street/road not steeper than 1:15 with 1.2m 

landings every 10m or 1:12 with landings every 5m both with top and bottom landings at 

least 1.2m clear of a door swing up to the principal entrance door. 

External Stepped approach 

Sites with a slope of more than 1:15 may be provided with a stepped approach as 

follows: 

An unobstructed width of at least 900mm with a firm hard non slip 

surface to all steps and landings 

Landings to be provided at the top & bottom of the steps at least 900mm 

long 

The rise of a flight must not exceed 1.8m between landings 

Steps to have a suitable tread nosing profile and uniform rise between 

75-150mm and a uniform going of 280mm (which for tapered treads should be 

measured at a point 270mm from the inside of the tread). 

Where there are 3 or more risers, a continuous handrail is to be 

provided on one side of the flight with a grippable profile fixed 850- 

1000mm above the step pitch line and extending 300mm beyond the top & bottom 

nosings. 

Even when a stepped approach is used, an accessible or level threshold as describe 

below should be provided. If a step is unavoidable, the rise should not exceed 150mm. 

Accessible level door thresholds into the building 

Level landings should be provided at the same level as the entrance door thresholds with 

a fall of 1:40 –1:60 away from the door separated from the building by proprietary tanking 

and a proprietary drained channel or 25mm max drainage slot- linked into the storm 

water drainage system. 

The door threshold should have a maximum 15º slope into the drainage channel/slot and 

provided with a proprietary raised threshold storm proof weather seal which should not 

exceed 15mm high (any projection more than 5mm should have chamfered or rounded 

edges) to allow safe unobstructed wheel chair access into the building 

. 

External door opening widths 

The external principal entrance door should have a minimum clear opening between the 

door leaf and doorstops of 775mm. 

Internal passageways/corridors widths 

Internal passageways/corridors should have minimum widths as set out in the table 

below: 

Doorway clear opening Corridor/passageway width* 

width mm 

mm 

750 mm or wider 

750 mm 

775 mm 

800 mm 

900 mm (when approached head on) 

1200 mm (when not approached head on) 



* Note: A corridor width of 750mm min is acceptable where there is a permanent 

obstruction not exceeding 2.0m in length, e.g. radiator or similar providing the obstruction 

it is not placed opposite a door that would prevent a wheel chair user turning. 

61

Internal stairs 

Minimum stair width for new dwellings is 900mm in the entrance storey suitable for 

disabled persons. 

Handrails must be provided on both sides of the stairs, at a height 900-1000mm above 

floor/nosing levels and continuous throughout their length suitable for disabled persons. 

Stairs, landings & guarding to be compliance with Part K of this guidance 

Accessible switches, sockets, controls etc 

All switches and sockets including the consumer unit, ventilation & service controls, door 

bells, entry phones, telephone points & tv/computer sockets etc, should be fixed between 

450-1200mm above floor level. Accessible consumer units should be fitted with a child 

proof cover or installed in a lockable cupboard. 

Provision of a ground floor W/C 

A W/C must be provided on the principal entrance storey with an outward opening door 

conforming to the above widths. The W/C enclosure/position should have a clear space 

of at least 450mm each side of the centre of the W/C with a clear space of at least 

750mm in front of the W/C pan to allow a wheelchair to approach within 400mm of the 

W/C from the front or within 250mm of the front of the W/C pan from the side. The 

washbasin is to be positioned not to impede access and the spaces outlined above. 

62

Part N: Safety glazing, opening & cleaning 

Safety glass and glazing 

Doors and adjacent sidelights/windows in critical locations within 1500mm of ground and 

floor level, and 300mm of doors and windows within 800mm of floor/ground to be safety 

glazed to: BS EN 12150, BS EN 14179, BS EN 14449, which supersedes BS 6206 in 

compliance with the following diagram: 

Diagram 17: Glazing in windows, partitions, doors, side panels/screens & walls 

Safety glazing must comply with the new system of marking which requires visible and 

clear and indelible markings on each piece of safety glazing within critical locations in 

compliance with: BS EN 12150, BS EN 14179, BS EN 14449 

63

Part P: Electrical safety 

Electrical Installations 

New or works to existing electrical circuits or systems must be designed, installed, tested 

and certified to BS 7671 or with the current editions of the IEE regulations by a 

competent person in compliance with Approved Document P of the Building Regulations. 

A competent electrician or a member of a competent person scheme must test and 

certify all such works. The electrician must provide signed copies of an electrical 

installation certificate conforming to BS 7671 for the owner of the property and a copy 

must be forwarded to the Building Control surveyor for approval at completion, so the 

Building Control completion certificate can be issued. 

All switches and sockets including the consumer unit, ventilation & service controls etc, 

should be fixed between 450-1200mm above floor level. Accessible consumer units 

should be fitted with a child proof cover or installed in a lockable cupboard. 

64

External works- paths, drives, patio & gardens 

New external paths to be shuttered 100mm thick conc. Mix type PAV 1, max bay size 6m 

with bitumen impregnated fiber board isolated Joints to BS 8110/5328 . 

New tarmac areas to be rolled 20mm base course of coated macadam with 6mm 

textured bitumen macadam wearing course with concrete edgings, to BS4987. 

New 60mm pre-cast self draining concrete block paving to clients choice, laid in 

compliance with manufacturers details, to BS6717. 

Concrete/natural stone slabs to clients choice, laid in compliance with manufacturers 

details to BS 7263:1 

Drainage of paved areas to be carried out in accordance with BS 6367:1983 A1 84 

and Approved Document H. Paths and paved areas to have a non slip finish with a fall of 

1:80 and a reverse gradient of at least 500mm away from walls of building. Surface water 

to be disposed of by an adequately sized and roddable drainage system via soakaways, 

or other approved means. 

65

Materials and workmanship 

All materials must comply with the following: 

British Standards or European Standards 

Product Certification Schemes (Kite marks) 

Quality Assurance Schemes 

British Board of Agreement Certificates (BBA) 

Construction Product Directives (CE Marks) 

Local Authority National Type Approvals (System Approval Certification) 

All materials must be fixed in strict accordance with manufacturers printed details and 

workmanship must be in strict accordance with BS 8000: Workmanship on Building Sites: 

Parts: 1 to 16. Where materials, products and workmanship are not fully specified or 

described, they are to be: Suitable for the purpose stated or inferred & In accordance 

with recognized good practice 

Guidance notes copyright 

Guidance notes copyright & produced by: Tony Gwynne, Forest of Dean District Council, 

Council Offices, High Street, Coleford, GL16 8HG. Tel: 01594 810000, 

Website: www.fdean.gov.uk E mail: building.control@fdean.gov.uk 

Acknowledgements: 

Front cover illustration by Apex Architecture Consultancy: 01594 516161 

Information for domestic sprinklers by Nationwide Fire Sprinklers Ltd: 0115 987 1110 

Important note: 

It should be made clear that whilst every care has been taken to in compiling this 

publication, and the statements it contains, no party or individual involved in this 

publication can accept any responsibilities for any inaccuracies. 

Additional building control services we can provide 

Building control can now provide the following services and manage them through your 

project as part of the service we offer: 

o SAP Calculations: Design Stage Calculations includes Residential Energy Performance 

Certificate and registration of certificate on completion. 

o Air Leakage Testing ( Residential & commercial) 

o SBEM Calculations 

o Code for Sustainable Homes Assessments 

o Renewable Energy Evaluations/Payback Reports etc 

o Fire Risk Assessments 

For more information, please contact Tony Gwynne, Mark Saunders or Simon Drake on 

01594 810000 

66

For further advice on Building Regulation issues in Gloucestershire 

please contact your local Building Control Service: 

Cheltenham and Tewkesbury Building Control Service 

Cheltenham Office: Municipal Offices, Promenade, Cheltenham, GL50 9SA 

Tel: 01242 264321 Fax: 01242 227323 Email: buildingcontrol@cheltenham.gov.uk 

Cotswold District Council 

Building Control, Trinity Road, Cirencester, GL7 1PX 

Tel: 01285 623000 Fax: 01285 653905 Email: building_control@cotswold.gov.uk 

Forest of Dean District Council 

Building Control Services, Council Offices, High Street, Coleford, GL16 8HG 

Tel: 01594 810000 Fax: 01594 812353 Email: building.control@fdean.gov.uk 

Gloucester City Council 

Building Control, 4 th Floor, Herbert Warehouse, The Docks, Gloucester, GL1 2EQ Tel: 01452 396771 

Stroud District Council 

Useful numbers of other agencies or companies 

Forestry Commission 01594 833057 

Sewage & Water Suppliers: 

Severn Trent Water 0800 783 4444 

Welsh Water/Dwr Cymru 0800 085 3968 

Environment Agency 08708 506 506 

Emergency Pollution Hot Line 0800 80 70 60 

Transco Gas Emergencies 0800 111 999 

Health & Safety Executive 01179 88 60 00 

Gloucestershire County Council 

General Enquiries 01452 425000 

Gloucestershire Fire & 

Rescue Service 01452 753333 

Highways Agency 0845 9 55 65 75 

(Amended Oct 2010 - Tony Gwynne) 

Fax: 01452 396763 Email: buildingcontrol@gloucester.gov.uk 

Building Control Services, Ebley Mill, Westward Road, Stroud, GL5 4UB 

Tel: 01453 754518 Fax: 01453 754511 Email: building.control@stroud.gov.uk 

67

building control guidance new dwellings & garages - Forest of Dean ...

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