Guidelines for the Removal of Typical Unauthorized Building Works ...

emoved portionGuidelines for the Removal ofTypical Unauthorized Building Works andGeneral Maintenance of External Walls

1. Preamble1.1 These guidelines provide guidance for the safe removal of typicalunauthorized building works (UBW) and general maintenance ofexternal walls.1.2 Removal of UBW is a kind of demolition work and is controlled underthe Buildings Ordinance. The removal work may generally beclassified into two types :(a) Those involving the demolition of a building or of anysubstantial or significant part of a building under an orderissued by the Buildings Department (BD)(i) An owner is required in such cases under the BO to appointa Registered Specialist Contractor (RSC), an AuthorizedPerson (AP) and a Registered Structural Engineer (RSE) tocarry out the work and to advise and ensure that necessarysafety measures are provided.(ii) In these cases, BD will specify in the relevant removal orderthat the appointment of these parties is required.(b) The removal of UBW which does not involve the demolition ofa building or of any substantial or significant part of a buildingunder an order by BD(i)In these cases, BD would not specify in the removal orderthat the appointment of RSC, AP and RSE is required.Instead, an owner would be asked in the removal order toappoint a contractor to ensure that the safety measures inthese guidelines are provided before and during the removalwork.

2. General2.1 Any person responsible for the removal of UBW, which is a kind ofdemolition work, or for general maintenance works is required toensure that the works are carried out in a safe manner.2.2 All works shall be carried out by competent and experienced contractorspecialized in the trade.2.3 Advice should be sought from building professionals for major repairor removal works involving e.g. UBW of solid constructions,appendages or advertisement signs with projections greater than 1mfrom the external wall, and for erecting scaffolds exceeding 15m inheight.2.4 Precautionary measures should be taken whilst working at high level,to prevent accidental falling of workers or building materials. Workersmust therefore wear a safety belt and keep it attached to a secureanchorage when working at high level. The removal of UBW mustproceed in the reverse order of construction. Adequate temporaryprops and ties should be provided to support and secure theconstruction elements before they are dismantled.2.5 Before commencing any removal work, a contractor should carry out ageneral survey of the UBW to be removed. The objective is to assessthe general condition of the UBW, how it was constructed, how itshould be removed and to ascertain the potential danger the removalwork may pose to public safety. The contractor should also find out ifthe UBW is over a public thoroughfare, another UBW or over abuilding which is occupied.2.6 He should then work out the necessary measures to protect publicsafety and the occupants of a building. These measures may includethe provision of temporary support to the UBW before it is removed,the provision of temporary platform under the UBW to protectmembers of the public or occupants under the UBW to be removed, theerection of catchfans to prevent the accidental falling out of smalldebris from the removal work, and whether the public area can betemporarily fenced off or the affected pedestrians diverted.2.7 All demolition operation should be carried out manually using handheldtools.2.8 Contractors should also observe the safety requirements issued by theLabour Department for the protection of workers, and the safety of thepublic when building material containing asbestoes is removed fromany UBW.

Figure 1: Truss-out bamboo scaffold

2.9 Reference should be made to the Code of Practice for ScaffoldingSafety published by the Labour Department on the safety requirementsand recommendations on planning, erection, maintenance, anddismantling of scaffolding.2.10 If a contractor has any doubt over the structural condition of an UBWor over the adequacy of the safety measures he proposes to provide, heshould not hesitate to consult the case officer of BD whose name andtelephone number are shown on the warning letter or covering letterattached to the relevant removal order.3. Warning3.1 It is an offence under s40(2B) of the BO for any person to carry outbuilding works in a manner resulting in injury to persons or damage toproperties. A person convicted of such offence is liable to a maximumfine of $250,000 and to imprisonment for three years.4. Typical UBW4.1 The following guidelines are provided for the removal of typical UBWin Hong Kong.(a)Unauthorized cages and small canopies projecting from externalwalls of buildings(i)Before the commencement of any removal work, a protectiveplatform should be erected under the UBW to prevent theaccidental falling of any debris or dismantled parts of theUBW. A typical detail of such a platform is provided in fig 1.(ii) Any household belongings, flower pots, etc in the UBWshould be removed before the removal of the UBW.(iii) Any timber or metal sheeting covering the UBW should beremoved first and retrieved into the main building to exposethe structural members of the UBW to be removed. This willassist the contractor to better assess how the UBW wasoriginally constructed and affixed to the main building, andhow the UBW should be removed.(iv) The steel structural members of the UBW should be cut byoxy-acetylene torch to small pieces and retrieved into themain building to complete the removal works.

Figure 2: Double row bamboo scaffold andworking platform over pavementNetWorkingplatformTarpaulinToeboardRakerShopStandardLedgerTransomPavement

(b) Unauthorized canopies and structures over public pavement orlanes(i)(ii)A timber or steel platform should be erected immediatelyunder the UBW to be removed. Typical details of suchplatform are provided in fig 2 and 3. Where any part of theprotective platform or scaffolding should be near thecarriageway, sufficient warning signs should be provided todrivers of motor vehicles.Where upon consulting the police, pedestrian traffic can betemporarily suspended or diverted from the pavement overwhich an UBW is to be removed. These measures should betaken to better protect the safety of the pedestrians.(iii) Demolition should generally be top down, i.e. in the order ofroof covering, beams, walls and columns.(iv)(v)Any household articles, furniture, etc in the lane structureshould be removed to reduce the loading before thedismantling of any structural members.Any timber or steel decorative sheeting on the UBW shouldbe removed in the first instance to expose the structuralmembers and the manner in which they are supported bythe main building.(vi) If the lane structure is constructed of heavy building materialsuch as bricks or concrete, these should be broken up inpieces, put into small bags and lowered onto the groundlevel as soon as they are dismantled.(vii) Where the structural members are heavy, temporary supportshould be provided underneath the members before they arecut into manageable size for removal.

Figure 3: Independent tied metal scaffold Through tie

(c)UBW erected on top of another UBW(i)(ii)Before the commencement of the removal of the UBW at thetop, all the occupants of the UBW below must be evacuated.Staff of BD will be able to assist where necessary byobtaining a Closure Order from the courts.A contractor should take note that any excessive loadingfrom building material dismantled from the UBW at the topcould cause the UBW at the bottom to collapse. Therefore,any building material or debris from the removal worksshould be put into bags and lowered to ground level as soonas they are dismantled.(iii) Similar methods of demolition and safety measures, as forthe removal of UBW over service lane provided aboveshould be followed.(iv) In addition, a double scaffolding should be provided aroundthe external perimeter of the UBW to be removed to providea working platform for the workers and as a protectivemeasure against the accidental falling of any small debris asindicated in fig 4.(d) Rooftop and flat roof structures(i) Before the commencement of any removal works, theexternal perimeter of the structures should be enclosed bydouble scaffolding to provide a working platform and toprevent the accidental falling of any small debris asindicated in fig 4.(ii) Where the UBW is adjacent to the external walls of the mainbuilding, a catchfan should be erected to protect the fallingoff of any small debris from the demolition works. Catchfanshall be installed at a vertical distance of not more than 10mbelow the working platform. A typical detail of suchcatchfan is provided in fig 5.(iii)The sequence of demolition should generally follow thosefor lane structures.(iv) Therefore, any debris from the demolition work should beput into small bags and transported through the mainbuilding to ground level as soon as they are removed fromthe UBW.(v)Any excessive loading could cause a danger to the mainbuilding.

Figure 4: Proper working platform on adouble row bamboo scaffoldNetStandardToe board :at least 200mmTransom (endprotrudes beyondledger for notless than 300mm)LedgerWorking platformat least 400mm wideGuardrail : at aheight of between 900mmand 1150mm above platform

Figure 5: Typical detail for bamboocatchfan and screen coverScreen tie at every 2mhorizontally andvertically over lappingwidth not less than300mmNetAnchor boltScreen tie atcatchfanWall tieSteel wires with anchor boltmaximum spacing 3m0.5mmmetal sheetAnchor boltNetTarpaulinBamboo with effectivediameter not less than 40mmBamboo maximumspacing 200mm centresWall tie1.5m(minimum)Notes :1. Bamboo for the construction of scaffold,and catchfanshall have an effective diameter not less than 40mm,2. Metal sheet, net and tarpaulin shall be fastened to thebamboo deck at 4 corners of the sheet or at spacingno less than 1.5m apart whichever is less.

5. Repair of external wall finishes,architectural features, windows etc5.1 Whilst carrying out general maintenance work to external walls ofbuilding, owners should ensure that such works are carried out withproper regard to public safety. A double bamboo scaffold withsuitable tarpaulin, netting and working platform should be erected onthe external walls to prevent the accidental falling of any debris beforethe commencement of any maintenance and repair work on externalwall. The scaffold shall be erected in double rows with transomsbetween the rows to provide a working platform at all working levelswhere work can be carried out safely. Bracing should be provided allover the inner and outer scaffold planes. Sufficient ties to the buildingstructure shall be provided to ensure stability.5.2 Catchfans shall be installed at a vertical distance of not more than 10mbelow the working platform, and at vertical intervals of not more thaneight storeys apart. A minimum clear headroom of 5.5m above streetlevel (within 500mm distance from edge of carriageway) should bemaintained to prevent any obstruction to vehicular traffic.5.3 Typical double row scaffold with working platform and catchfan hasalready been given in fig 4 and 5.Buildings DepartmentApril 2002