45 Access for maintenance CI/Sfb: (75) UDC: 624.059 Uniclass: MX22 KEY POINTS: Health and safety considerations are of the highest priority Design that does not take maintenance into account is unacceptable
particular building types in non-industrial areas. For industrial areas and cities the interval between cleans should be halved.
Contents 1 Method and frequency of cleaning 2 Access 3 Internal access 4 External access 5 Roof suspension systems 6 Bibliography
2 ACCESS
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2.01 Internal or external access? Type of access is decided by: and frequency of cleaning • Method and running costs • Capital cleaned by tenants or professional window cleaners • Whether Safety requirements • Appearance of equipment when not in use. •
1 METHOD AND FREQUENCY OF CLEANING 1.01 Method The methods by which windows and facades are to be regularly cleaned and maintained must be considered at an early stage of design, and the necessary equipment incorporated into the structure. Recent incidents and subsequent legislative measures reinforce this, and failure to ensure proper provision may result in very expensive remedial work. Regular washing with cold or warm water (sometimes with a mild detergent) is normally adequate, applied either by swab with chamois leather to dry and scrim to polish; or by squeegee, which is much quicker over large areas and when used from cradles. Between 400 m2 and 500 m2 in eight hours is average, using a squeegee in ideal conditions. 1.02 Frequency Table I shows some recommendations for frequency of washing according to locality, and Table II gives frequency of washing
A general guide to selecting external types of access is shown in 45.1. When selecting internal types of access, take into account possible problems: of window (especially high-rise housing) • Type of cleaning adjacent exterior cladding • Method draughts and disruption to air-conditioning when opening • Freak windows to furniture and activities; possible damage to • Disruption property cost of providing opening windows (for cleaning from • Relative inside) against cost of cradle (for cleaning from outside) (beware cleaners, especially tenants, having to lean out to • Safety clean adjacent fixed lights). Cleaning the internal glass face is usually no problem unless inaccessible. Often two separate contractors are given the work of cleaning the inside and outside faces. Cleaning the outside from the outside will usually give better results, and can effect long-term savings over the extra cost of providing opening windows to allow cleaning from inside.
Table I Recommended frequency of cleaning per year Location
Ground floor facing street
Other windows
Rooflights
London postal area and smoky industrial areas of large cities Semi-industrial towns Non-industrial towns
16
8
2
12 8
6 4
2 1
Table II Recommendations for frequency of washing of particular building types Type of building
Side windows
Rooflights
Offices Public offices, banks, etc Shops
Every 3 months 2 weeks Outside every week Inside every 2 weeks Outside daily Inside every week 3 months 3–4 months 2 weeks 4 weeks 2 months 4–6 weeks
Every 12 months 3 months 6 months
Shops (in main streets) Hospitals Schools Hotels (first class) Factories (precision) Factories (heavy work) Domestic (by contract)
3 months 6 months 12 months 3 months 3 months 6 months –
Ground-floor windows facing streets should be cleaned at twice this frequency
45.1 Chart for selecting system for external access 45-1
45-2
Access for maintenance
3 INTERNAL ACCESS 3.01 Ergonomics Human dimensions related to window cleaning are shown in 45.2 to 45.5. and Table III.
3.02 Types of window To avoid accidents with small children, all opening windows, except possibly those less than 1.5 m above the ground outside, should now be fitted with devices to prevent them normally opening to leave a gap more than about 100 mm. This device has to be removeable for cleaning purposes, but the method should obviously be child proof. When any degree of leaning-out to clean windows is involved, a safety harness linked to an internal anchorage must be used. Two such examples are shown in 45.6.
45.2 Exterior reach to adjacent fixed light through opening light. Shaded area is average acceptable size for ease of cleaning
45.6 Two situations where cleaning access is from the inside, but when a properly anchored safety harness should be used 45.3 Interior reach to fixed, reversible or pivot window casements should have offset pivot hinges to give • Side-hung minimum 100 mm gap, set well forward of the frame which
• • • • 45.4 Reach becomes less over bench or worktop
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should not be fixed more than 100 mm in from the external face. Consider using Continental-type inward-opening casements which solve most window-cleaning problems. Double-opening windows have both side hinges and hopper hinges allowing for easy cleaning and safety. Hopper windows opening inwards must be low and narrow for easy cleaning. If high and large, they can be dangerous. Vertical and horizontal sliding sash windows should not be used for internal cleaning. Horizontal and vertical pivot windows are satisfactory for internal cleaning if they can be fully reversed and securely fixed with locking bolts both when reversed for cleaning and open normally for ventilation. Sliding projecting windows can be dangerous for internal access cleaning unless maximum depth is 750 mm, but even then cleaning can be hazardous.
4 EXTERNAL ACCESS 4.01 Manual cleaning: access from ground Type of access can be initially assessed from 45.1. Manual cleaning methods with access from the ground include:
45.5 Dimensions of fixed light heights and guard rails for domestic buildings
foot: maximum window height 1.8 m providing there are no • On awkward projections. part ladder: up to 3 m, but awkward with long horizontal • Single windows (use travelling ladders – see para 4.02. Long-handled squeegee can sometimes be used instead.
Access for maintenance
45-3
Table III Access to external faces from the inside Note: shaded area indicates glass face Good
Satisfactory
Bad
(2) Outward opening with extending hinges
(3) Outward opening
Casement
(1) Inward opening Double opening hopper
(4)
(5) Inward opening
(6)
(7) Outward opening
Vertical slide
(8)
(9)
Horizontal slide
(10) Top corner reach possible (see 45.2)
(11) Corner reach not possible
Horizontal pivot
(12) Completely reversible
(13) Not completely reversible and too high (see 3)
Vertical pivot
(14) Completely reversible
(15) Not reversible but at correct height (see 45.3)
(16) Not reversible and too high (see 44.3)
(Continued)
45-4
Access for maintenance Table III (Continued) Good
Satisfactory
Bad
(17) Top-hung opening in
(18) Top-hung opening out is impossible to clean
Top hung
Fixed adjacent
(19) Corner reach possible
(20) Corner reach impossible
(21) Centre reach possible
(22) Centre reach impossible
(24) Inward opening casement
(25) Top-hung opening. Too large and distorts when held by corner
Access to internal faces Double glazing
(23) Fully reversible pivot
over 3 m must be secured. Maximum 9 m, safe inclina- • Single stepladder in the form of a mobile trestle. Maximum • Ladders tion 83 . Securing can be with mechanical anchorage, as to the height is 5.4 m. ground, 45.7. The top of the ladder can be restrained using • Lightweight portable scaffolding. Height is maximum three times proprietary ‘D’ wheels, 45.8a. These rubber wheels with holleast base dimension unless weighted, tied back to building, or
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lows between the rib and the hub are stiff enough to stay round, 45.8b, when the ladder top to which they are fixed is moved up or down the wall. When the ladder is in use, the wheel is pressed against the wall and becomes the D-shape that holds it securely, 45.8c. Mechanical ladder on mobile chassis. Can be either freestanding or leant against a wall. More rigid than simple ladders but still only gives access to limited areas.
45.7 Ladder with feet supported and fixed in natural ground
outriggers fitted. Special scaffolds can be made to suit building design. Provides safe, rigid platform leaving both hands free.
45.8 Ladder with top restraint (Ladderfix Ltd). a ‘D’ wheels fitted to ladder. b D wheel able to roll. c D wheel under load
Access for maintenance
staging in light, hinged aluminum alloy sections each • Zip-up 2.14 m high 1.6 m long 1.35 m wide. Height is maximum four
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times least base dimension, but outriggers and restraint can increase this ratio. Again, variations are possible to suit building design. Mobile folding and telescopic platforms, only for use as secondary access for difficult areas. Generally of fixed height between 12 m and 15 m.
4.02 Manual cleaning using permanent access There are five main possibilities: but only if all windows can be reached, otherwise • Balconies: some other forms of access will be needed. and ledges: if continuous, more useful to a professional • Sills window cleaner than a balcony. Construction Regulations 1966
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suggest 630 mm as minimum width, but some cleaners will accept 300 to 500 mm width. A ledge from which a fall of 2 m or more is possible must be provided with either a guard rail or a continuous safety harness anchorage, as in 45.9. Ledges requiring the operative to clip, unclip or reclip his safety harness while on the ledge are not acceptable. Catwalks: mainly for lateral movement. Must be level and nonslip. Maximum gradient of 20 . with regularly spaced stepping laths for sloping roofs; above 20 needs steps. Internal catwalks need 2 to 2.15 m headroom. Minimum footing width 630 mm (870 mm if materials put on gangway): guard rails between 900 mm and 1150 mm above platform when more than 2 m
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45-5
above ground; toe boards 150 mm deep with maximum distance of 750 mm between the board and lowest guard rail. Fixed ladders: use steps up to 70 , rungs over 70 pitch, 45.10. and 45.11. Vertical ladders not recommended, but where necessarily used must be caged. Use landings every 6 m height positioned to break fall, or use metal mesh safety cage over the ladder. Travelling ladders: with top and bottom fixings on continuous rail or channel to allow ladder to slide along and round the facade. Useful for long bands of glazing up to 4.5 m high; can be fixed at almost any angle.
5 ROOF SUSPENSION SYSTEMS 5.01 Temporary systems These are usually hired and erected and dismantled each time. There are two systems: system as shown in 45.12. Rather unwieldy and • Counterweighted limited; roof structure and parapet must be capable of taking load. davits as shown in 45.13. Same problems as the counterweight • Fixed system but safer, although horizontal traverse is more difficult. There are also a few proprietary portable gantry systems. 5.02 Permanent systems: trolley units A permanent system is usually desirable and for frequent cleaning soon covers the extra initial cost; but unless carefully designed and integrated with the structure and facade it can look very unsightly.
a
b 45.9 A continuous wire cable with harness-clip that rides through the anchor fixings (Latchways plc). a Fixing to a wall. b In use
45-6
Access for maintenance
45.13 Fixed davits on a roof with parapet
45.10 Fixed ladder leading to interior catwalk
45.11 Recommended dimensions for fixed ladders and landings, based on Construction Regulations 1966 (with additional information from Industrial Data Sheet 53) (Australian Department of Labour). a up to 70 x ¼ head clearance, min 1050 mm for 60 slope, 950 mm for 70 slope z ¼ steps, minimum width 100 mm, 200 to 250 mm rise flight width 450 to 750 mm. b over 70 with cage
45.12 Cradle using counterweight system To balance C T ¼ W O for safety C T should not be less than three times W O
45.14 Hand-operated roof trolley travelling on twin track. The boom can be lowered to the horizontal to deal with projections on the face of the building
45.15 Bosun’s chair in performed plastic
Access for maintenance
45-7
45.16 Standard timber cradle. a Side elevation. b End elevation. c Plan
a
b
c
d
45.17 Mullion guides. a Standard mullion. b Roller on guide to prevent lateral movement. c Casters on guide to prevent outward movement. d Standard roller
In all cases roof structure and finishes must be able to carry the imposed loads. There are two elements to consider: the roof trolley system and the suspended chair or cradle (see para 5.03) There are two trolley systems:
operated cradle. A typical standard timber cradle is • Manually shown in 45.16. Not recommended for heights over 30 m. cradle. Sizes range from 1.8 to 9 m width; • Power-operated materials can be steel, aluminium or GRP.
roof trolley consisting of a continuous rail, often RSJ, • Manual positioned about 450 mm in front of the wall face, to which the
In all cases some form of manual or mechanical chair or cradle restraint, and of independent safety harness for the occupants, must be provided. The only method to provide continuous restraint is a mullion guide, 45.17.
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cradle is attached by ropes and castors. The most common is a pair of continuous rails, fixed to the roof about 750 mm apart, on which runs a cantilevered trolley, 45.14. Powered roof trolley is the most efficient and safest and is essential for heights of over 45 m. It is also the most expensive, but can be relatively cheap for large buildings. It must be considered at the very earliest design stages. The general principle is the same as the manual trolley except that the unit is powered. Power supply needed is 440 V three-phase.
5.03 Suspended units There are two basic types: chairs and cradles: Bosun’s chair, 45.15, extensively used for awkward areas and • always used with manual gantries. A modern version is the facing bicycle, with pedals to work the winch.
6 BIBLIOGRAPHY General The Construction (Health, Safety and Welfare) Regulations 1996 BS 5974: 1990, Code of practice for temporarily installed suspended scaffolds and access equipment BS 6037: 1990, Code of practice for permanently installed suspended access equipment BS 8213: Part 1: 1991, Code of practice for safety in use and during cleaning of windows and doors SI 1998/2307 Lifting Operations and Lifting Equipment Regulations 1998
45-8
Access for maintenance
SI 1997/831 Lifts Regulations 1997 SI 1999/3242 Management of Health and Safety at Work Regulations 1999 SI 1998/2306 Provision and Use of Work Equipment Regulations 1998 SI 1999/1148 Water Supply (Water Fittings) Regulations 1999
Health and Safety Executive publications HSG 150 Health and safety in construction GS 42 Tower scaffolds CIS No 5 Temporarily suspended access cradles and platforms GS 31 Safe use of ladders, step ladders and trestles