building control guidance domestic loft conversions - Forest of Dean ...

BUILDING CONTROL 

GUIDANCE 

FOR 

DOMESTIC LOFT CONVERSIONS 

- 1 - 

OCTOBER 2010 EDITION 4

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 

loft conversions to 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. For loft conversions of four storeys or more with more than one floor above 4.5m please 

contact building control for advice. 

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 listed below are available 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 non-standard 

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); 

L1B: Conservation of fuel and power in existing dwellings (2010 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 Dwellings, New extensions 

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 CONVERTING AN EXISTING LOFT SPACE 6 

2.0 ENGAGING A PROPERTY PROFESSIONAL 

3.0 OBTAINING BUILDING REGULATIONS APPROVAL 

3.1 full plans application 

3.2 building notice application 7 

4.0 EXEMPT BUILDINGS AND WORK 

5.0 COMPETENT PERSON SCHEME 

6.0 PLANNING PERMISSION, LISTED BUILDING & CONSERVATION AREA CONSENTS 8 

7.0 THE PARTY WALL ACT 1996 

8.0 CONSTRUCTION (DESIGN AND MANAGEMENT) REGULATIONS 2007 (CDM) 

9.0 ASSESSING THE FEASIBILITY OF YOUR LOFT CONVERSION 9 

10.0 GENERAL TECHNICAL & PRACTICAL GUIDANCE FOR LOFT CONVERSIONS 10 

A1: PREPARATION, PROTECTION, ACCESS & DEMOLITION 

A2: INSPECTION OF THE EXISTING ROOF & STRUCTURE 

A3: ALTERATION, MODIFICATION & STRENGTHENING OF THE EXISTING ROOF/STRUCTURE 

Diagram 1: Typical plan layout of a loft conversion with dormer pitched roof 11 

Diagram 2: Typical section through a loft conversion with dormer pitched roof 12 

Diagram 3: Typical section through a loft conversion with dormer flat roof 

A4: NEW PITCHED ROOFS 13 

Pitched roof coverings 

Pitched roof structure 

Roof trusses (including attic & girder trusses) 

Cut roof construction 

Table 1: Spans for Common Domestic Timber Rafter Sizes at 400mm spacing 14 

Table 2: Spans for Common Domestic Timber Ceiling Joist Sizes at 400mm spacing 

Table 3: Spans for Common Domestic Timber Purlin Sizes 

Table 4: Permissible Clear Spans for Common Ceiling Binders Sizes 15 

Diagram 4: Typical section through a pitched roof 

Roof restraint 

Roof insulation 16 

Table 5: Insulation laid horizontally between and over ceiling joists 

Table 6: Insulation fixed between/under rafters 

Table 7: Insulation fixed between/over rafters 

Diagram 5: Typical roof valley detail 17 

Diagram 6: Typical section through a dormer roof 

Roof ventilation 18 

A5: FLAT ROOF CONSTRUCTION 

Diagram 7: Typical section through a flat (cold) roof 19 

Table 8: Spans for Common Flat Roof Joist Sizes 

Table 9: Insulation Fixed Between/Under Flat Roof Joists 20 

Table 10: Insulation Fixed above Flat Roof Joists 

Valleys and lead work 

Lofts hatches, doors & Light wells to roof spaces 

A6: NEW EXTERNAL WALLS 21 

Cavity walls 

Table11: Insulation requirements for external cavity walls 

External timber framed walls with render finish 22 

Diagram 8: Typical section through external timber framed walls with render finish 

External timber framed walls with cladding finish 

Diagram 9: Typical section through external timber framed walls with cladding finish 23 

Wall abutments 

Lintels & weep holes 

Structural columns/beams etc 

Expansion joints 

Strapping and restraint 

Cavity closers 

A7: INTERNAL LOAD BEARING WALLS 24 

Internal load bearing timber stud walls 

Diagram 10: Typical section through internal load bearing timber stud wall supporting 

roof loads 

Table 12 : Insulation requirements to exposed timber framed walls 

Internal load bearing masonry partitions 

A8: INTERNAL NON LOAD BEARING PARTITIONS 25 

Internal masonry non-load bearing partitions 

Internal timber studwork non-load bearing partitions 

- 3 -

A9: UPGRADING EXISTING EXTERNAL WALLS 26 

Diagram 11: Typical plan layout of upgrading existing walls in loft conversion 

Table 13: Insulation requirements for upgrading existing external walls 

A10: SEPARATING (PARTY) WALLS & FLOORS BETWEEN DWELLINGS 27 

Masonry party walls separating dwellings 

Timber frame party walls separating buildings 

Upgrading sound insulation of existing separating walls 

Party floors separating buildings 

Sound testing requirements 

A11: ADDITIONAL PROVISIONS FOR 3 STOREY BUILDINGS/EXTENSIONS 28 

Compressive strength of masonry units 

A12: INTERMEDIATE UPPER FLOOR(S) 

Diagram 12: Typical section through a loft floor 

Diagram 13: Typical section through an upper floor 29 

Table 14: Spans for Common Domestic Floor Joist Sizes 

Table 15: Spans for Common Trimmer Joist supporting Trimmed Joists 

Table 16: Spans for Common Trimming Joist supporting Trimmer Joist 

Sound insulation to floors within the dwelling 30 

SVP pipe boxing 

Exposed intermediate upper floors 

Table 17: Insulation requirements to exposed intermediate floors 

PART B: FIRE SAFETY & MEANS OF ESCAPE 31 

MEANS OF ESCAPE FROM SINGLE STOREY DWELLING WITH NEW SECOND STOREY 

MEANS OF ESCAPE FROM TWO STOREY DWELLINGS WITH NEW THIRD STOREY 32 

Option 1: Protected stairway 

Option 2: Protected stairway with alternative exits at ground floor level 33 

Option 3: Fire separated 3 rd storey with alternative external/internal fire exit 34 

Option 4: Residential sprinkler systems for means of escape 35 

Fire doors 

Smoke alarms 

Fire resistance to new storey floor 36 

Permitted building openings in relation to a boundary: 

Openings within 1.0m of a boundary 

Openings more than 1.0m from a boundary 

Table 18: Permitted unprotected areas in relation to a relevant boundary 

Fire resistance to elements of structure etc 

Table 19: Fire resistance to common elements of structure etc 

Surface spread of flame: wall & ceiling linings 37 

Table 20: Surface spread of flame: Classification of wall & ceiling linings 

PART C: SITE PREPARATION AND RESISTANCE TO CONTAMINANTS & MOISTURE 38 

Horizontal damp proof courses & trays (dpc’s) 

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

PART D: CAVITY WALL FILLING WITH INSULATION BY SPECIALISTS 

PART E: RESISTANCE TO THE PASSAGE OF SOUND 

New Internal walls & floors in loft conversion 

New/existing party walls and floors in loft conversion 

PART F: VENTILATION 39 

Purge (natural) ventilation 

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

Background ventilation 

Mechanical extract ventilation rates 

General requirements for mechanical extract ventilation 

PART G: SANITATION, HOT WATER SAFETY AND WATER EFFICIENCY 40 

PART H: DRAINAGE AND WASTE DISPOSAL 41 

H1: FOUL WATER DRAINAGE 

Foul, rain & storm water drainage systems 

Waste pipes 

H2: SEPTIC TANKS, SEWAGE TREATMENT SYSTEMS & CESSPOOLS 42 

Existing septic tank & effluent drainage 

Non mains foul drainage waste water treatment systems 

Septic tanks 

Sewage treatment systems 43 

Treatment of sewage from septic tanks & sewage treatment systems 

Drainage fields 

Drainage mounds 

Wetlands/reed beds 44 

Percolation test method to calculate area of drainage field for septic tanks 

or sewage treatment systems. 

Diagram 14: Typical section through a septic tank/sewage treatment system drainage field 45 

Diagram 15 : Typical drainage field plan layout (not to scale) 

- 4 -

H3: RAINWATER DRAINAGE AND HARVESTING 46 

Rainwater gutters and down pipes 

Table 21: Gutter sizes & pipe outlet sizes for drainage of roof areas 

Rainwater/ grey water harvesting storage tanks & systems 

Surface water drainage around the building 

PART J: COMBUSTION APPLIANCES & FUEL STORAGE SYSTEMS 47 

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 22: Air supply (ventilation) to solid fuel appliances 48 

Carbon monoxide alarms 

Table 23: Sizes of flues in chimneys 

Construction of masonry chimneys 49 

Construction of factory made flue block chimneys 

Construction of factory made metal chimneys 

Configuration of flues serving open flue appliances 

Inspection & cleaning openings in flues 

Interaction of mechanical extract vents & opened flue solid fuel appliances 

Chimney heights 50 

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 51 

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 52 

STAIRS, LANDINGS AND CHANGES IN LEVEL OF 600MM OR MORE (INCLUDING EXTERNAL STEPS) 

Diagram 16: Measuring rise & goings 

Diagram 17: Typical internal stair case & guarding construction details 53 

GUARDING TO EXTERNAL STEPPED ACCESS, BALCONIES, FLAT ROOFS 

& LOW LEVEL WINDOW OPENINGS 

PART L: CONSERVATION OF FUEL AND POWER IN EXISTING DWELLINGS 54 

LISTED BUILDINGS, CONSERVATION AREAS & ANCIENT MONUMENTS 

AREAS OF EXTERNAL WINDOWS, ROOF WINDOWS & DOORS 

NEW THERMAL ELEMENTS 

External glazing 

Table 24: U Values for new external windows & doors including roof windows 

Closing around window & door openings 

Sealing Measures 

External Walls, roofs, floors & swimming pool basin 55 

Table 25: U Values for new external walls, roofs, floors & swimming pool basin 

RENOVATION/UPGRADING OF EXISTING THERMAL ELEMENTS 

Table 26: Renovation/upgrading of existing thermal elements 

Payback report 

ENERGY EFFICIENT LIGHTING 56 

Fixed internal lighting 

Fixed external lighting 

CONSEQUENTIAL IMPROVEMENTS 

COMMISSIONING OF FIXED BUILDING SERVICES 

PROVIDING INFORMATION -BUILDING LOG BOOK 

PART N: SAFETY GLAZING, OPENING & CLEANING 57 

Safety glass and glazing 

Diagram 18: Glazing in windows, partitions, doors, side panels/screens & walls 

PART P: ELECTRICAL SAFETY 58 

Electrical Installations 

EXTERNAL WORKS- PATHS, DRIVES, PATIO & GARDENS 59 

MATERIALS AND WORKMANSHIP 60 

ADDITIONAL BUILDING CONTROL SERVICES WE CAN PROVIDE 

GLOUCESTERSHIRE BUILDING CONTROL DEPARTMENTS CONTACT DETAILS 61 

USEFUL NUMBERS OF OTHER AGENCIES OR COMPANIES 

- 5 -

1.0 Converting an existing loft space 

Converting an existing loft space can be an easy and cost effective way of increasing living 

accommodation in most houses. This guide to loft conversions will provide useful guidance on 

how some of the technical design and construction requirements of the Building Regulations 

can be achieved where the loft space of an existing one or two storey dwelling is being 

converted into habitable accommodation to form an additional storey to the dwelling. Where the 

house has three or more storeys before the loft is converted -please contact building control for 

further guidance. 

2.0 Engaging a property professional 

This type of work can be complex and unless you are experienced in construction you will need 

to get some professional advice 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 this type of work, 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. 

3.0 Obtaining Building Regulations approval 

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

proposed works. 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: 

3.1 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. 

- 6 -

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. 

3.2 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 and the required fee. 

The application forms are available to down load from our web site at: 

www.fdean.gov.uk. 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. 

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. 

4.0 Exempt buildings and work 

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

providing no part is used as 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. 

5.0 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. For a list of all 

scheme members go to www.competentperson.co.uk 

- 7 -

6.0 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. 

7.0 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 

8.0 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. 

- 8 -

9.0 Assessing the feasibility of your loft conversion 

Before commencing a loft conversion it is important to assess the feasibility of the project. This 

will involve inspection of the existing loft & dwelling to assess the following: 

Roof structure & shape- The overall form, construction and profile of the roof will have a major 

bearing on the whether the roof is suitable for conversion to a usable space. Traditional cut 

timber pitched roofs with gable ends walls (cavity walls or solid walls at least 250mm thick) and 

horizontal ridges are generally easier to convert and can normally support structural beams than 

hipped roofs or roofs with intersecting pitches and valleys which may require more complicated 

structural designs. 

Trussed rafter roofs constructed using a series of complex trusses should only be altered, 

modified and converted in compliance with details and calculations carried out by a suitable 

qualified and experience property professional. No trussed rafter should ever be cut or modified 

in any way until a new supporting structure is in place which has been designed by a suitably 

qualified and experienced specialist designer. Further information for loft conversions with 

trussed rafter roofs can be obtained from TRADA at: www.tra.org.uk 

All existing timbers should be in a sound condition, any defective timber is to be replaced with 

new in compliance with details and calculations carried out by a suitable qualified and 

experience property professional. Existing timbers are to be inspected and where necessary 

treated against insect and fungal attack by a suitable qualified and experience specialist. 

Roof Coverings & roofing felt - Should be in a sound and weather tight condition; any 

defective coverings/felt should be replaced with matching new/existing sound coverings, fixed 

as manufacturer’s details. 

Ceilings- To the underside of the new storey floor should achieve 30 minutes fire resistance. 

Normally 13mm plaster board & skim or sound lath and plaster in older houses will achieve this, 

otherwise additional upgrading will be required. 

Internal space available – The roof space should not have any chimneys or services passing 

centrally through the loft space that cannot be easily moved, altered or modified by suitable 

experienced and qualified property professionals. Structural alterations/modifications should be 

in compliance with details and calculations carried out by a suitable qualified and experience 

property professional. 

Head room available- Is measured vertically from the top of the new floor (which typically can 

be 200mm above the existing ceiling joists) to the underside of the new horizontal/sloping 

ceilings (which can typically down stand 50 -75mm from the existing roof structure). A minimum 

headroom of 2.0m is required at the head of the stairs to comply with building regulations. A 

ceiling height of 2.2 to 2.3 is preferred in the centre of the roof in habitable rooms reducing to 

0.800 to 1.2m for the side walls on sloping ceilings so low furniture can be placed in front of 

them. If your existing roof pitch is less than 30 degrees and roof span is less than 6 metres, a 

loft conversion may be impractical and the only possibility may be to remove the roof completely 

and replace it with attic trusses suitable for rooms in the roof designed by a specialist. 

Means of escape- Three storey houses will require a protected stairs that connects to a hall 

and final exit at ground floor level or give access to at least two escape routes to final exits at 

ground level which will require separated by fire resisting construction and fire doors. 

Alternatively, the new top storey can be separated by fire resisting construction and provided 

with an alternative escape route (subject to planning permission), or a domestic sprinkler 

system can designed by a fire engineer. The full means of escape and fire safety requirements 

are covered in detail later in this guidance. 

- 9 -

10.0 General technical & practical guidance for loft conversions 

A1: Preparation, protection, access & demolition 

Provide all necessary scaffolding, access ladders, material hoists, temporary protection and 

working platforms etc for the loft conversion which are to be erected, maintained, certificated, 

dismantled and removed by suitably qualified and insured specialists. 

All plumbing, drainage, heating, electrical services etc including re-siting of heating appliances/ 

boilers/ flues /tanks etc to be altered /modified /adjusted as necessary by suitably qualified & 

experience specialists or registered competent persons, tested & appropriate certification 

issued where required in this specification. 

Any asbestos is to be inspected by a specialist, removed and disposed off site by a specialistlicensed 

contractor in compliance with the Control of Asbestos Regulations 2006. 

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. 

The builder is to allow for and maintain all temporary protection to the building to maintain 

weather tightness until completion of the works. 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%. 

A2: Inspection of the existing roof & structure 

Existing foundations, lintels and wall structure that will be built off or support the new storey 

loads from the proposed works may need to be exposed at the discretion of the Building Control 

Surveyor and structural engineer to ensure that they are adequate and suitable - this may 

include opening up or excavating walls/floors (and making good to match the existing) to check 

internal foundations or walls. If they do not appear to be adequate to support the proposed 

works, details/justification of the proposed remedial works/alterations including necessary 

engineering calculations and details will need to be submitted for approval before works 

commence on site. 

A3: Alteration, modification & strengthening of the existing roof & structure 

Over haul existing roof coverings and structural timbers as necessary, replace defective and 

missing tiles, treated timber battens, roofing felt, lead valleys, flashings, facia boards, soffit/ 

barge boards and rainwater goods etc as necessary to match existing. Repoint/ rebuild 

defective masonry walls/ chimneys etc as necessary. Repair/ replace defective roof timbers as 

necessary. Existing timbers to inspected, repaired, replaced and treated as necessary by a 

specialist with a warrant backed guarantee against insect & fungal attack. 

Alteration/modification/strengthening of the existing roof structure/structural members/ walls etc 

should only be carried out/repaired/ replaced/ supported or removed in strict compliance with 

details and calculations received from a suitably qualified person. These details must be 

approved by building control before works commence on site. 

Trussed rafter roofs constructed using a series of complex trusses should only be altered, 

modified and converted in compliance with details and calculations carried out by a suitable 

qualified and experience property professional. No trussed rafter should ever be cut or modified 

in any way until a new supporting structure is in place which has been designed by a suitably 

qualified and experienced specialist designer. Further information for loft conversions with 

trussed rafter roofs can be obtained from TRADA at: www.tra.org.uk 

- 10 -

Diagram 1: Typical plan layout of a loft conversion with dormer pitched roof (not to scale) 

Existing walls with a 

threshold U value worse 

than 0.7, upgrade U value 

to 0.55 for cavity walls & 0.3 

for solid walls as follows: 

13mm vapour checked 

plaster board & skim 

75 x 50mm timber studs at 

400mm ctrs 

fixed to wall 

Thermal insulation fixed 

between studs as guidance 

details 

Proposed dormer 

roof omitted for 

clarity of layout 

Internal sound insulated stud 

partition as guidance details 

FD 20 fire 

door 

13mm vapour checked plaster board & skim 

12mm structural plywood skin & fixings to s/engineers details & 

calculations 

100mm timber studs at 400mm ctrs 

Thermal insulation fixed between studs as guidance details 

Load bearing studs supported by structural beams to 

s/engineers details & calculations 

- 11 - 

13mm vapour 

checked plaster 

board & skim 

75 x 50mm timber 

studs at 400mm ctrs 

fixed to wall 

Insulation fixed 

between studs as 

guidance details 

Smoke alarm 

30 minutes fire 

resisting (& 

sound 

insulating) stud 

partition to 

protect stairs as 

guidance 

details 

Stairs & handrail 

as guidance 

details 

Load bearing stud with thermal 

insulation as detailed below 

EXISTING SEPARATING 

WALL 

Upgrade sound 

insulation to separating 

walls between dwellings 

as necessary as 


ADJOINING 

UNHEATED ROOF 

SPACE

Diagram 2: Typical section through a loft conversion with dormer pitched roof (not to 

scale) 

Roof insulation -see options 

in guidance notes 


plaster board with 

skim finish 

Roof insulation & ventilation 

as detailed on other 

roof pitch 

12mm plywood gusset screwed 

High level roof vents equal to 

a continuous 5mm air gap with 

fly screen if not breathable 

type felt 

If existing rafter undersized fix 

additional rafters alongside 

existing -birds mouthed over 

& fixed to structural stud 

joist 

hanger 

Ceilings to achieve 


resistance from under 

side 

Eaves ventilation required equal to a 

continuous 25mm air gap with fly screens 

both sides of roof if not breathable type 

felt 

Structural stud partition as 

s/engineers details, insulated as 

detailed in guidance notes, with 

13mm 

v.c.plaster board and skim finish 

Structural beam to s/engineers 

details & calculations 

Existing roof coverings 

Trimming joists & 

rafters to 

s/engineers details 

& calculations 

Ceiling joists- see guidance 

notes for sizes 

Floor joist sizes - see guidance 

notes for sizes suitable for spans 

and spacing for noggins 

Sound insulation - see guidance notes 

22mm thick moisture resistant t & g floor boards 

Note: see guidance notes for fire safety 

requirements, stairways /guarding 

details & checking exisitng foundations 

& lintels to support new storey loadings. 

Diagram 3: Typical section through a loft conversion with dormer flat roof (not to scale) 

Bitumen bedded stone chippings covering the whole roof surface to a depth of 13mm 

To achieve a class AA designation in close proximity of boundary for spread of flame 

Treated flat roof joists fixed to beam with heavy duty galvanized hangers, 

fixed to treated wall plates bolted to web of beam. Flat roof joist sizes 

and spacing to suit clear spans as guidance notes 

Strip back & refix roof coverings with new roofing felt & treated battens 

as necessary, dress flat roof membrane over plywood & tiling fillet 

(150mm min above flat roof) to provide water proof junction. Provide 

temporary protection & support as guidance notes 

Suggested ridge detail- steel ridge beam supported on pad stones into 

load bearing walls/intermediate load bearing columns, with 50mm 

deep treated timber plate bolted to top of beam, rafters birds mouthed 

over plate and mechanically fixed. 

High level roof vents equal to a continuous 5mm air gap with fly 

screen if not breathable type felt increase to 25mm to cross 

flat roof (excludes warm roofs) 

If existing rafter undersized fix additional rafters alongside 

existing -birds mouthed over & fixed to structural stud 

Roof insulation -see options in guidance notes 

13mm vapour checked plaster board with 

skim finish 

joist 

hanger 

Ceilings to achieve 


resistance from under 

side 

Eaves ventilation required equal to 

a continuous 25mm air gap with 

fly screens both sides of roof if 

not breathable type felt 

Lay fiberglass insulation between 

joists and additional layer across joists 

(or other approved) as guidance 

details. Ensure 50mm clear 

air space to underside of non 

breathable felts at eaves junction 

Lay 150mm fiberglass insulation 

between joist and additional 

170mm accross joists or other 

approved (U value 0.16). Ensure 

50mm clear air space to underside 

of non breathable felts at eaves 

junction 

Ceiling joists-see guidance 

notes for sizes 

Structural stud partitions as 

s/engineers details, insulated as 

detailed in guidance notes, with 

13mm v.c.plaster board and 

skim finish 

Structural beams to s/engineers 

details & calculations 

Floor joist sizes - see guidance 

notes for sizes suitable for spans 

and spacing for noggins 

Sound insulation - see guidance notes 

22mm thick moisture resistant t & g floor boards 

- 12 - 

Roof insulation -see options 

in guidance notes 

Dormer roof constructed as typical roof 

section detail and supported on timber 

wall construction with finishes to match 

existing or as stated in planning permission. 

See guidance noted for construction details. 

Trimming joists and rafters supporting dormer 

roofs to s/engineers details and calculations. 

Double glazed window and means of escape 

openings as detailed in guidance notes 

Code 5 lead flashings 

High level roof vents as main roof 

Eaves ventilation required 

equal to a continuous 25mm 

air gap with fly screens both 

sides of roof if not breathable 

type felt 

Roof insulation and eaves 

ventilation as detailed on other 

roof pitch 

NOTE: Alterations to existing 

roof structure including removal 

of structural members etc must 

be in compliance with structural 

engineers details & calculations 

which must be approved by 

building control before works 


NEW FLAT ROOF 

Single ply polymeric or three ply built up felt roofing in bitumen water proof 

coverings applied by flat roofing specialist as spec. 

22mm external quality plywood decking or other approved 

Treated timber firing strips cut to 1:60 min gradient- laid with falls to gutter (allow 

50mm min air gap in depth of firing strip from u/side of deck to top of insulation 

50mm min air gap 

Note: see guidance notes for fire safety requirements, stairways /guarding 

details & checking exisitng foundations & lintels to support new storey loadings. 

Insulation fitted below roof deck (cold roof & will require cross ventilation as 

detailed) or insulation fixed above deck (warm roof and will not require any 

ventilation). See guidance notes for flat roof insulation options 

13mm plasterboard with foil backing or 500g polythene to provide a vapour check 

50mm welted drip on galvanized plate to centre line of gutter fixed to 75mm deep 

timber nosing piece 

Matching Upvc gutters, facia/barge board with 25mm continuous air gap 

with insect screen 

Timber lintel to s/engineers details & calculations 

Matching double glazed window fitted with means of esape 

openings in bedrooms (or inner rooms) see guidance noted for 

details 

Matching painted render on stainless steel lath with drained cavity 

or vertical tile cladding on insulated stud walls - see guidance 

notes for details 

Code 5 lead flashings (and soakers to tile/roof junction) 

Proprietary high level roof vents equal to a continuos 5mm air gap 

fitted with insect screen 

NOTE: Alterations to existing roof structure 

including removal of structural members 

etc must be in compliance with structural 

engineers details and calculations 

which must be approved by building 

control before works commence on site.

A4: New pitched roofs 

Pitched roof coverings 

Roof covering to consist of matching 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-tear able 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. 

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. 

- 13 -

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 the 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. 

Table 1: Spans for Common Domestic Timber Rafter Sizes at 400mm spacing 

(Strength Class C24) 

Slope of Roof (degrees) 

15-22 22-30 30-45 

Size of Rafter 

Maximum clear span (m) 

Breadth X Depth (mm) 

47 100 

47 125 

47 150 

47 170 

47 195 

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 

Table 2: Spans for Common Domestic Timber Ceiling Joist Sizes at 400mm spacing 


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

Slope of Roof (degrees) 

Size of Purlin 

Breadth X Depth 

(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 

- 14 -

Table 4: 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 

Diagram 4: 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 

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 

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. 

- 15 - 

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

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 5: Insulation laid horizontally between and over ceiling joists 

(Vented cold roof achieving a U-value of 0.16 W/m².k) 

Product K -Value Position in roof 

Crown Wool & 0.036-0.037 150mm between joists & 

Rock-wool Roll 

Alternatives TBA 

150mm laid across joists 

Table 6: Insulation fixed between/under rafters 

(Vented cold roof achieving a U-value of 0.18 W/m².k) 


Kingspan Kooltherm K7 0.020 100mm friction fixed between 

rafters & 

Or other approved with a K 

value of 0.020 


0.021 42.5mm fixed under rafters* 

* 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 7: Insulation fixed between/over rafters 

(Warm roof achieving a U-value of 0.18 W/m².k) 


Kingspan Kooltherm K7 




0.020 50mm fixed between rafters & 

55mm fixed over rafters 

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

breathable roofing membrane as manufacturers details 

- 16 -

Diagram 5: 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 

Diagram 6: 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) 

13mm vapour checked plaster 

board & skim 

- 17 - 

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 

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

Roof ventilation 

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) 

A5: 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 coverings: 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 or in compliance with the Lead Sheet Associations technical guidance sheets 

available from: www.leadsheet.co.uk. 

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 Table 14 below to form a 

‘warm roof’ (or alternatively insulation fixed between/under joists in compliance with Table 13 

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 9 below. 

Surface finish to flat roofs: to consist of bitumen bedded stone chippings covering the whole 

surface to a depth of 12.5mm to achieve a class AA, AB or AC 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 13 & 14 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 ie insulation above the structural deck do not require 

ventilation. 

- 18 -

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. 

Diagram 7: 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 

Water proof coverings applied by flat roofing specialist as spec. 

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 

Table 8: 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 

- 19 - 

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 

Insulation to achieve a min U value of 

0.2, fixed above or below structural 

decking as above tables 

Plasterboard with vapour check 

Welted drip 

Rain water gutters, facia/ 

barge board 

25mm continuous air gap 

with insect screen

Table 9: Insulation Fixed Between/Under Flat Roof Joists 

(Vented ‘cold roof’ achieving a U-value of 0.18 W/m².k) 


Kingspan K7 

Kingspan K18 

Or other approved with a 

K value of 0.020 

0.020 

0.021 

- 20 - 

140mm between joists (2 x 70mm) 

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 10: Insulation Fixed above Flat Roof Joists 

(Non vented ‘warm roof’ achieving a U-value of 0.18 W/m².k) 

Product K -Value Insulation fixed above deck 

Kingspan Thermaroof 




0.020 120mm fixed above deck in a single 

layer 

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.

A6: New external walls 

Cavity walls (U-value 0.28 W/m².k - area weighted average value) 

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 dry lining. Where 

required external natural stone facings to be tied to external block work with wall ties as detailed 

below and foundation widths increased by 150mm. 

Walls to be built with 1:5/6 cement mortar and tied with BBA approved stainless steel wall ties 

suitable for cavity width at maximum spacing of 750mm horizontal (increased to 600mm if 

retaining partial fill insulation using proprietary retaining rings as manufacturers details), 450mm 

vertical and 225mm at reveals, verges and closings for cavities up to 100mm wide. 

Cavity width and insulation details to be constructed as Table 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. 

Table11: 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 40 mm Kingspan 90mm 100 mm insulation 

Kooltherm K8 or 

block (k value 0.15 or 

Other approved with 


lower) 

50mm 50 mm Kingspan 100mm 100 mm dense 

Kooltherm K8 or 

concrete block (K 


Full fill 

Other approved with 


value 1.13) 

n/a 115mm full fill glass n/a 100 mm insulation 

fiber (K value 0.037) 

block (k value 0.15 or 


Suitable for full fill 

lower) 

- 21 -

External timber framed walls with render finish (U-value 0.28 W/m².k - area weighted 

average value) 

Render finish (to comply to BS 5262) - to match existing or as specified to be 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- ‘Tyveck 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: 100/150mm x 50mm head & sole 

plates and vertical studs at 400mm ctrs, to s/engineers details & calculations. Thermal insulation 

board in compliance with table below to be tightly friction fixed between studs with 13mm 

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 8: 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) 

100 x 50mm treated stud at 400mm 

ctrs 

Thermal insulation as guidance 

details 


board & skim finish 

100 x 50mm soleplates fixed to base 

Construction details as 

guidance 

External timber framed walls with cladding finish (U-value 0.28W/m².k - area 

weighted average value) 

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 100 X 50mm 

timber studs at 400mm ctrs with 100 X 50mm timber head & sole plates & 2 rows noggins and 

diagonal bracing as S/Engineers details. Studs exceeding 2.5m high to be designed by 

Structural Engineer. Thermal insulation board in compliance with table below to be tightly 

friction fixed between studs with 13mm 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. 

- 22 -

Diagram 9: Typical section through external timber framed walls with cladding 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 

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. 

- 23 - 

100 x 50mm treated stud at 400mm 

ctrs 

Thermal insulation as guidance 

details 


board & skim finish 

100 x 50mm soleplates fixed to base 

Construction details as 

guidance

A7: Internal load bearing walls 

Internal load bearing timber stud walls 

Load bearing timber stud walls to be in compliance with details and calculations by a suitably 

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


Typically load bearing stud walls not exceeding 2.5m high are to be constructed of 100 x 50mm 

C24 soft wood studs fixed vertically at 400mm ctrs with head and sole plates and intermediate 

noggins fixed at 600mm, with thermal insulation friction fixed air tight between studs as detailed 

in table below, with 12mm thick structural plywood glued & screwed to the full height & width of 

the room side face of the stud wall and finished with 15 mm plasterboard and skim. Insulated & 

draught proofed access hatches to be formed between studs. New rafters to be birds mouthed 

over and mechanically fixed to head plate, and mechanically fixed to existing rafters by an 

approved method. 

Diagram 10: Typical section through internal load bearing timber stud wall supporting 

roof loads (not to scale) 

Table 12 : Insulation requirements to exposed timber framed walls (U-value 0.28 W/m².k) 

Insulation Type Minimum Thickness mm 

Kingspan Kooltherm K12 or other 

90 mm 

approved with a K value of 0.020 


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 

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. 

- 24 - 

New rafter fixed alongside existing, birds mouthed 

over & mechanically fixed over new stud 

100 x 50mm timber head plate 

100 x 50 vertical timber studs at 400mm ctrs 

Thermal insulation friction fixed tightly between studs 

12mm structural plywood glued & screwed to studs 

15mm vapour checked plaster board & skim 

100 x 50 timber sole plate 

New structural beam supporting load bearing stud 

to s/engineers details & calculations

A8: Internal non load bearing partitions 

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 studs, fixed 

vertically at 400mm ctrs with head and sole plates and intermediate noggins fixed at 600mm 

with a minimum of 25 mm of 10Kg/m² proprietary sound insulation quilt suspended in the stud 

and finished with 15 mm plasterboard and skim both sides. 

- 25 -

A9: Upgrading existing external walls 

Where existing external walls are to be used as part of the loft conversion and have a threshold 

U-value worse than 0.7, the U-values should be upgraded to 0.55 for cavity walls & 0.3 for solid 

walls. Upgrade walls typically using 75 x 50mm soft wood studs at 400mm ctrs fixed vertically to 

existing walls with mechanical fixings (with a strip of damp proof course between stud & wall if 

there is a risk of moisture penetration), thermal insulation to be friction fixed air tight between 

studs as detailed in table below and 15 mm vapour checked plasterboard fixed to studs with 

plaster skim finish. Existing solid external walls less than 328mm thick in rendered stone or 

brick or less than 250mm thick in rendered blockwork, should be tanked internally with a BBA or 

other approved tanking system to prevent the ingress of moisture into the building. 

Diagram 11: Typical plan layout of upgrading existing walls in loft conversion (not to 

scale) 

Table 13: Insulation requirements for upgrading existing external walls 

External wall type Insulation Type Minimum 

Cavity walls with threshold Uvalue 

worse than 0.7, upgrade U- 

value to 0.55 

Solid walls with threshold U-value 

worse than 0.7, upgrade U-value 

to 0.30 

Existing walls with a 

threshold U value worse 

than 0.7, upgrade U value 

to 0.55 for cavity walls & 0.3 

for solid walls as follows: 


plaster board & skim 

75 x 50mm timber studs at 

400mm ctrs fixed to dpc 

strip & existing wall 

Thermal insulation fixed 

between studs as guidance 

details 

Solid external walls less than 

328mm thick rendered 

stone/brick or less than 

250mm thick rendered 

blockwork to be tanked 

internally with a BBA 

approved water proof 

tanking system to prevent 

ingress of moisture into the 

building 





- 26 - 

Thickness mm 

60 mm 

70mm

A10: Separating (party) walls & floors between dwellings 

( 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-value of 0.2 W/m 2 .K. 

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. 

Upgrading sound insulation of existing separating walls 

Existing wall should be at least 100mm thick, of masonry construction and plastered on 

both faces. With other types of existing wall the independent panels should be built on 

both sides. 

Construct new independent frame fixed at least 10mm from one side of the existing wall 

using either; 100 x 50mm timber studs at 400mm ctrs fixed onto head & sole plates or to 

a proprietary galvanised metal frame, fixed as manufacturers details. Fix 50mm thick 

ROCKWOOL RWA 45 sound insulation or other approved (min density 16kg/m3) friction fixed 

between studs 

Fix two layers of 15mm thick dB checked wall board with staggered joint and plaster skim 

finish to the independent frame using mechanical fixings. Note- allow a minimum 

distance of 35mm between face of existing wall & inner wall board face. 

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. 

- 27 -

A11: Additional provisions for 3 storey buildings/extensions 

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 to 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. 

A12: 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 the 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. 

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. 

Diagram 12: Typical section through a loft floor (not to scale) 

Steel beam to s/engineers 

details & calculations with 

100 x 50mm timber plate 

bolted to top flange. 

(beam fixed above existing 

ceiling joists on pad stones) 

- 28 - 

22mm thick moisture resistant t & g floor boards fixed to joists 

Floor joists fixed between existing joists. Joists sizes, 

spacing & noggins suitable for clear spans as guidance 

notes & tables 

100mm thick sound insulation as guidance notes 

Ceilings to achieve 30 minutes fire resistance from 

under side 

Heavy duty galvanised hangers supporting floor 

joists. Hangers fixed to timber plate bolted into 

web of beam using 12mm high tensile bolts at 

800mm ctrs

Diagram 13: 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 

specification) 

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 

Table 14: Spans for Common Domestic Floor Joist Sizes (Strength Class C24) 

Size of joist 


(mm) (mm) 

47 97 

47 120 

47 145 

47 170 

47 195 

47 220 

75 220 

Spacing of joist (mm) 

400 450 600 


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 15: Spans for Common Trimmer Joist supporting Trimmed Joists 


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 16: 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 

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 

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 

- 29 - 

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

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 

mineral wall sound insulation quilt. 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. 

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-value 0.22w/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. 

Table 17: Insulation requirements to exposed intermediate floors 

U-value 0.22 W/m².k 

Insulation Type Minimum Thickness 

Jablite Jabfloor 70 

Celotex & Kingspan 

Polyfoam 

Rockwool Rockfloor 

- 30 - 

125 mm 

70 mm 

100 mm 

120mm

Part B: Fire safety & means of escape 

Means of escape from single storey dwelling with new second storey 

The conversion of Bungalows or similar single storey building to form a new first floor do not 

require a protected hall, landing or fire doors, but the supporting floor must still be provided with 

30 minute fire resisting construction. The stair may be positioned in a ground floor room such as 

living room, provided there is an external door that opens directly to the outside for means of 

escape. All rooms or bedrooms on the first floor (except bathrooms or toilets) must be directly 

accessible off the stair landing. Smoke detection must be installed as detailed below, with an 

additional interlinked heat detector at ceiling level in kitchens which are open to the stairs at 

ground level. 

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 

the guidance sections below & ADB1- par 2.6 (a) or (b). 

- 31 -

Means of escape from two storey dwellings with new third storey 

4 options are available: 

Option 1: Protected stairway 

The new and existing stairs, landings and hallway from the new 3 rd storey down to the ground 

floor must be protected and enclosed in 30-minute fire resisting construction and the protected 

stairs must discharge directly to an external door as diagram below. 30 minutes fire resisting 

construction is required to the underside of the new upper storey floor. 

DINING KITCHEN 

ALL PARTITIONS 

ENCLOSING THE STAIRS 

IS TO HAVE 30 MINUTES 

FIRE RESISTANCE 

INCLUDING GLAZING* 

LOUNGE HALL 

FD20 

FD20 

SD 

UP 

BED 2 BED 3 

Key to works indicated on diagram above 

FD 20: 20 minute fire resisting door to BS 476-22:1987 fitted with intumescent strips rebated 

around sides & top of door or frame excludes toilets/bathrooms/en-suite providing the partitions 

protecting the stairs has 30 minutes fire resistance from both sides. Existing doors can be 

upgraded with proprietary intumescent paint/paper system. (Note: self closing FD30 fire door 

with intumescent strips, smoke seals & 100mm high fire resistant thresholds is required 

between the dwelling/garage) 

SD/HD: Interlinked mains operated smoke alarm/heat alarm with battery back up fitted at ceiling 

level to BS 5446 & installed to BS 5839 pt6 

Note: Where applicable, any glazing in walls enclosing the protected stairs is to have 30 

minutes fire resistance and located 1.1m min above the floor level, and unlimited in the fire 

doors. No glazing is permitted elsewhere including between the dwelling & garage unless 30 

minutes fire insulated glazing & beading system is installed. 

BED 1 

- 32 - 

FD20 

FD20 

ALL PARTITIONS FD20 





LANDING 

SD 

BATH 

UP 






NEW BEDROOM 

FIRE SEPARATION AT 

SECOND STOREY LEVEL 

FD20 

SD 

ALTERNATIVELY THE FIRE 

SEPARATION CAN BE PROVIDED AT 

THE BOTTOM OF THE STAIRS AT 

FIRST FLOOR LEVEL 

ENSUIT 

UP

Option 2: Protected stairway with alternative exits at ground floor level 

The new and existing stairs, landings and hallway from the new 3 rd storey down to the ground 

floor must be protected and enclosed in 30-minute fire resisting construction and the protected 

stairs must give access to 2 or more FD20 fire doors on the ground floor that discharge into 

different rooms which are separated from each other by 30 minute fire resisting construction 

both of each must have external doors for escape as diagram below. 

KITCHEN/DINING ROOM 






LOUNGE 

U/SIDE OF STAIRS TO 

HAVE 30 MINUTES 


FD20 

FD20 

SD 

UP 

cupb 

BED 2 BED 3 

BED 1 








SD/HD: Interlinked mains operated smoke alarm/heat alarm with battery backup fitted at ceiling 






FD20 

- 33 - 

FD20 

ALL PARTITIONS FD20 





LANDING 

SD 

BATH 

UP 






NEW BEDROOM 



FD20 

SD 



THE BOTTOM OF THE STAIRS AT 


ENSUIT 

UP

Option 3: Fire separated 3 rd storey with alternative external/internal fire exit 

The new top 3 rd storey should be separated from the lower storeys by 30 minute fire resisting 

construction and provided with an alternative escape route leading to its own final exit as 

diagram 3. 

The external stairs must not be within 1.8m of any unprotected opening at the side of the stairs, 

and no openings are permitted below the stairs- unless the opening is fitted with 30 minute fire 

resisting glass and proprietary bead system and is permanently sealed shut- subject to 

adequate ventilation. 

The external stairs is subject to obtaining planning permission etc where necessary before the 

works commence on site. (Please contact the FODDC planning department for further 

information). 

The alternative fire exit can also be formed internally as a protected stairway. 

DINING KITCHEN 

LOUNGE HALL 

SD 

UP 

BED 2 BED 3 

BED 1 








SD/HD: Interlinked mains operated smoke alarm/heat alarm with battery back up fitted at ceiling 






- 34 - 

LANDING 

SD 

BATH 

UP 

EXTERNAL FIRE EXIT STAIRS 

(CAN BE AN INTERNAL 

PROTECTED STAIRS) SEE 

GUIDANCE NOTES 

NEW BEDROOM 



FD20 

SD 




PARTITIONS ENCLOSING THE STAIRS IS 

TO HAVE 30 MINUTES FIRE RESISTANCE 

INCLUDING ANY GLAZING* 

ENSUIT

Option 4: Residential sprinkler systems for means of escape 

Where fire safety requirements of the building regulations cannot be met for loft conversions, 

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 4 options 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. 

Fire doors 

All rooms onto the protected stairs (except bathrooms or toilets providing the enclosing walls 

have 30 minutes fire resistance) are to be provided with FD20 (or FD30) fire doors to BS 476- 

22:1987 fitted with intumescent strips rebated around sides & top of door or frame with 

intumescent strips. Any glazing within the fire door or stairway enclosure is to have 30 minutes 

fire resistance including the beading as detailed in above options. 

Existing solid/hardwood doors may achieve the required 20 minutes fire resistance or can be 

upgraded with proprietary intumescent products applied as manufacturers details to achieve 20 

minutes fire resistance, as agreed with building control before works commence on site. Contact 

Cotswold Intumescent Products on: 01453 731006. A copy of the purchase invoice will be 

required by building control on completion to confirm product used. 

Doors between garages and dwellings to have 100mm high fire resisting threshold step down 

into the garage, FD30 fire door & frame fitted with an approved mechanical self closing devise, 

intumescent strips and cold smoke seals. 

Smoke 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) 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. 

- 35 -

Fire resistance to new storey floor 

The new 3 rd storey floor storey should be separated from the remainder of the house by 30 

minute fire resisting construction e.g. a minimum of 12.5 mm (if existing or 15mm if renewed) 

plasterboard and skim to ceilings and sides of stud walls and provided with a 20 minute fire door 

with intumescent strips at either the bottom or top of the new stair leading to the loft conversion. 

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 18: 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 

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 19: Fire resistance to common elements of structure etc 

Building element Fire resistance 

- 36 - 

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: 13mm 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 

13mm 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 20: 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. 

IMPORTANT NOTE: Means of escape windows – are not required where the stairs is 

protected as detailed above 

- 37 -

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. 

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 

Part E: Resistance to the passage of sound 

New Internal walls & floors in loft conversion 

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 . 

New/existing party walls and floors in loft conversion 

Sound insulation details for new party walls and floors and upgrading of existing party walls 

and floors to be carried out in accordance with the relevant details contained within this 

guidance and Approved Document E . 

- 38 -

Part F: Ventilation 

Purge (natural) ventilation 

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. 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 in two 

story buildings, direct access to a protected stairs (or protected route to inner rooms) is 

acceptable in compliance with the guidance above. Escape windows are not required where 

protected routes are provided in compliance with this guidance. 

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. 

Background ventilation 

Background ventilation to be provided equivalent to 8000mm² to habitable rooms and 2500mm 2 

to wet rooms via hit and miss or 2 stage catches fitted to windows 

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) 

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 

- 39 -

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. 

Where a building is converted into a new dwelling, the bath should be fitted with an in line 

blending valve fixed at 48 degrees centigrade. 

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 

- 40 -

Part H: Drainage and waste disposal 

H1: Foul water drainage 

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 double sealed with 

holding down bolts to covers & 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. 

- 41 -

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. 

- 42 -

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. 

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 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 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. 

- 43 -

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 


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 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. 

- 44 -

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

field (not to scale) 

Diagram 15 : 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 


2000mm min separation 

- 45 - 

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

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 21: 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. 

- 46 -

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) 

- 47 -

Table 22: 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 extension (good air tightness) 

In existing building (if air tightness 

improved- use figure for new extension) 

Enclosed stove with no flue draught 

stabilizer 

In new extension (good air tightness) 

In existing building (if air tightness 

improved- use figure for new extension) 

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 

300mm 2 /kW for first 5kW & 850mm 2 / 

kW of balance of appliance rated out 

put 

550mm 2 /kW of appliance rated out put 

550mm 2 /kW for appliance rated out put 

Above 5kW 

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 23: 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 

- 48 -

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. 

- 49 -

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. 

- 50 -

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. 

- 51 -

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 

` 

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. There is no minimum stair width for new 

extensions or replacement stairs in existing dwellings. 

Handrails must be provided on one side of the stairs, at a height 900-1000mm above 

floor/nosing levels and continuous throughout their length. 

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. 

- 52 - 

top surface of tread 

rise 

top surface of tread

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 

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

External stairs & landings 

As internal stair guidance details above 

Handrail & guarding 

at least 900mm high 

above pitch line 

tread 

non climable balustrades 

& no gaps to exceed 

100mm 

rise 

All guarding must 

resist a horizontal 

force of 

0.36kn/m 

outer string 

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. 

- 53 - 

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

Part L: Conservation of fuel and power in existing dwellings 

Listed buildings, conservation areas & ancient monuments 

If the proposed energy efficiency requirements will unacceptably alter the character or 

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

conservation area, then the energy efficiency standards 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 in compliance with paragraphs 3.6- 3.14 of AD L1B. 

Areas of external windows, roof windows & doors 

Area of external windows, roof windows & doors should not exceed the sum of 25% of 

the usable internal floor area of the extension, plus the total area of any windows or 

doors which as a result of the extension works, no longer exists or are no longer exposed 

in compliance with paragraph 4.2 of ADL1B. 

Where necessary, SAP Calculations to be sent to building control to confirm design 

flexibility where area of external windows, roof windows & doors exceed 25% of the 

usable floor area. 

Building control can provide SAP calculations to confirm design flexibility where the area 

of external windows, roof windows & doors exceed 25% of the usable floor area if 

required. Please contact Building Control on 01594 810000 for more details 

New thermal elements 

External glazing 

External glazing insulation details to comply with U-values for external windows, doors & 

roof lights in compliance with paragraphs 4.19- 4.22 & Table 1of ADL1B as follows: 

Table 24: U Values for new external windows & doors including roof windows 

Fitting Insulation standard U value: W/m 2 .K 

Windows, roof window or roof light 1.6 (or WER as Band C of par 4.22 of ADL1B) 

Doors with more than 50% glazing 1.8 

Other doors 1.8 

Replacement windows/doors 1.2 centre pane- if external appearance of facade 

or character of the building is to be maintained 

Typically, double glazed units with 16mm air gap and factory sealed with low-E coating & Argon 

filled in timber or Upvc frames will achieve a U-value of 1.6. Manufacturers details will be 

required for other types of frames to confirm minimum U values in compliance with the above 

table. All external doors, windows, roof lights to be draft stripped 

Closing around window & door openings 

Checked rebates should be constructed to window/door reveals or proprietary finned insulated 

closers should be used. Checked rebates are where the outer skin masonry/skin projects 

across the inner skin by at least 25mm, the cavity is closed by an insulated closer and the 

window or door is fully sealed with mastic or similar externally. 

Sealing Measures 

All external door and window frames, service penetrations to walls, floors 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. 

- 54 -

External Walls, roofs, floors & swimming pool basin 

External Walls, roofs, floors & swimming pool basin to comply with new thermal element 

requirements in compliance with paragraphs 5.1- 5.6 & Table 2 of ADL1B as follows: 

Table 25: U Values for new external walls, roofs, floors & swimming pool basin 

Element Insulation standard U value: 

W/m 2 .K 

Walls (exposed & semi exposed) 0.28 

Pitched roof & dormer windows with 

insulation at ceiling level 

0.16 

Pitched roof & dormer windows with 

0.18 

insulation at rafter level 

Flat roof or roof with integral insulation 0.18 

Floors 0.22 

Swim Swimming pool basin (walls & floor) 0.25 

See Part A: Structure for wall, roof & floor construction details incorporating the above insulation 

requirements. 

Renovation/upgrading of existing thermal elements 

Where the existing walls, roof, floor, windows or doors is to be retained and become part of the 

thermal envelope or renovated or subject to a material change of use and are un- insulated 

below the threshold values in column (a) of table below then the thermal elements should be 

thermally renovated/upgraded to the U values in column (b) in table below. (Note: this only 

applies where the area to be renovated is more than 50% of the surface area of the individual 

element and 25% of the total building envelope, and is technically and functionally feasible with 

a simple payback of 15 years +), as follows: 

Table 26: Renovation/upgrading of existing thermal elements 

Element (a) Threshold 

Cavity walls (where suitable for filling with 

insulation) 

Solid walls 

Floors 

Pitched roof- insulation at ceiling level 

Pitched roof- insulation between rafters 

Flat roof or roof with integral insulation 

- 55 - 

U-valueW/m 2 .K 

0.7 

0.7 

0.7 

0.35 

0.35 

0.35 

(b) Upgraded 

U-valueW/m 2 .K 

0.55 

0.30* 

0.25** 

0.16 

0.18 

0.18 

* Lesser standard acceptable where reduces floor area by 5% 

** Lesser standard acceptable where new work would effects existing-adjoining 

floor levels. 

Note: Insulation details and method of upgrading existing thermal elements to be agreed 

with the building control surveyor before works commence 

Payback report 

Building control can provide a payback report for the renovation/ upgrading of thermal 

elements if required– please contact Building Control on 01594 810000 for further 

details.

Energy efficient lighting 

Fixed internal lighting 

fixed internal energy efficient lighting in new extensions must not be less than 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 

Fixed external lighting 

Fixed external energy efficient lighting in new extensions must consisting of either; 

(i) Lamp capacity not greater than 100 lamp-watts per light fitting and fitted with 

automatic switch off between dawn and dusk and when lit area becomes unoccupied; 

or 

(ii)Lamp efficacy greater than 45 lumens per circuit-watt; and fitted with automatic switch 

off between dawn and fitted with manual controls. 

Consequential improvements 

(applies to existing buildings with a total useful floor area over 1,000m 2 ) 

Consequential improvements (additional work) are required to make an existing building 

more energy efficient which has a total useful floor area exceeding 1,000m 2 and 

is subject to an extension or provision of fixed building service in compliance with 

paragraphs 6.1- 6.5 of ADL1B & section 6 of ADL2B 

Commissioning of fixed building services 

Copy of commissioning certificate for fixed building services is to be sent to Building 

control within 5 days of completion of the commissioning work being carried out (or within 

30 days for works commissioned by a person registered with a competent persons 

scheme) 

Providing information -building log book 

Log book containing the following information is to be provided in the dwelling on 

completion: 

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 

- 56 -

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 18: 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 

- 57 -

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. 

- 58 -

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. 

- 59 -

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 copy right 

Guidance notes copy right & 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 

- 60 -

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 Fax: 01452 396763 Email: 

buildingcontrol@gloucester.gov.uk 

Stroud District Council 

Building Control Services, Ebley Mill, Westward Road, Stroud, GL5 4UB 

Tel: 01453 754518 Fax: 01453 754511 Email: building.control@stroud.gov.uk 

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) 

- 61 -

building control guidance domestic loft conversions - Forest of Dean ...

Create successful ePaper yourself

Delete template?

Save as template?