Scaffolding in New Zealand - Best Practice Guideline for
SECTION 4: TUBE AND FITTING SCAFFOLDING - Continued
4.7. Erecting working and access platforms
4.7.1 Specifications of working platforms and access platforms
A platform is a structure or deck on a scaffold to support workers, material or plant.
Working platforms and access platforms (other than suspended work platforms) should be erected using either scaffold planks or prefabricated platform units. Each working platform should be designed and constructed to support the intended loads imposed on it. Every working platform should be decked as close as practicable to the work face of the structure it is being used with.
Working platforms
Working platforms need to be wide enough to accommodate workers, materials and plant - a minimum of 675mm wide (deck width) for non proprietary scaffolds, but maintaining a clear unobstructed access of not less than 450mm wide for all scaffolds. For example, if material or plant 500mm wide is intended to be stacked on the working platform, the working platform (deck width) would have to be a minimum of 950mm wide. This will allow a minimum clear unobstructed access of not less than 450mm.
Access platforms
Access platforms should be a minimum of 675mm wide for non proprietary scaffolds.
4.7.1.1 Proximity to the working face
Planks or decking forming the surface of a work or access platform should be as close as practicable to the work face. The maximum permissible gap between the working platform and the work face is 300mm. As a rough guide, then, a scaffold standard with 48.3mm outside diameter should not exceed 250mm from the work face to the standard. If the scaffold is required to be more than 300mm from the working platform, inside guardrails or an alternative means of edge protection is required (see figure 32).
The maximum gap permitted on a working or access platform itself is 50mm.
Figure 32: Proximity of
scaffolding to the working
face
4.7.1.2 Inside planks
On a planked light duty tube and fitting scaffold it is acceptable to have one or two inside planks cantilevered onto an extended putlog tube or transom. Generally on a butt planked scaffold the putlogs are connected to the ledgers with single (putlog) couplers. Do not use double flap or butterfly single couplers on any cantilevered tube unless it is supported by a brace preventing uplift. If you are required to erect three or more inside planks on a butt plank scaffold the cantilevered tube needs to be supported by a brace. Under sling an additional ledger under the cantilevered putlog tubes or transoms with double couplers (R/A couplers) then attach the brace to the lower ledger as shown in figure 33. Planks must be secured to prevent displacement.
Figure 33: Inside planks and their support
4.7.1.3 Guardrails and midrails
Guardrails, including midrails, must be provided on the exposed sides and end of all working platforms regardless of height. The height of the midrail should be equidistant between the top guardrail and the working platform or alternatively equidistant between the top of the toeboard and the top of the guardrail.
For non proprietary scaffolds, the height of the top guardrail must be no less than 0.9m and no more than 1.1m from the platform.
When secured to the standard or upright member, each guardrail must be capable of independently sustaining at any point a 700N (71kg) vertical force or a 450N (46kg) horizontal force without failure, undue deflection, or permanent reset of the position of the guardrail.
Guardrails for H-Frame scaffolds should have the intersection of the cross braces at approximately 1.0m above the working platform.
The midrail should then be placed at approximately 0.5m above the working platform. Midrails may be excluded on lifts that do not include working platforms.
4.7.1.4 Toeboards or kickboards
A toeboard or equivalent protection must be fitted to the outside and end of every platform. The toeboard must protrude a minimum of 150mm above the working platform to prevent dislodgement of materials and tools.
Toeboard should be secured to standards with wire, single couplers or specialised toeboard fittings. Ideally toeboards should extend no less than 150mm above the intended tools or materials stacked on the working platform e.g. if materials are stacked 350mm high on a working platform, toeboards should be a minimum of 500mm high.
Scaffolds erected in high pedestrian areas should use both toeboards and screening.
4.7.1.5 Maximum height of scaffolds and working platforms
The maximum height of a scaffold constructed in accordance with these guidelines is 33.0m to the top-working platform. Scaffolds that exceed 33.0m in height must be constructed to: a chartered engineer's design statement, certificate or letter; or a producer statement where such a statement is required to be provided to a Building Consent Authority for the issue of a Building Consent or a Code Compliance Certificate in relation to the Building Act 2004; or, for proprietary scaffolds, the manufacturer's specifications.
If the involvement of a chartered engineer is required, generally you will have to provide the following information:
- Detailed plan view, showing dimensions and scaffold bay layout.
- Detailed cross section of the scaffold in relation to the work face, showing transverse bracing and plank levels.
- Detailed elevation showing longitudinal bracing and position of ties.
- Detailed section of the proposed ties and what the ties are connected too.
- Detailed list of scaffold components and their weights.
- Screening information, such as weight and porosity, may be required to work out the wind load on the scaffold.
- The intended use of the scaffold.
- The duty loading of the scaffold.
The engineer may also require soil samples to ascertain the load capacity of the ground the scaffold is to be erected on and for the design of adequate soleboards. Note that if a scaffold exceeding 33.0m to the top working platform is altered structurally by the scaffolder without approval of the engineer the liability for the scaffold design transfers directly to the scaffolder making the unauthorised changes.
For the stability of scaffolds above 33.0m additional transverse bracing (dogleg or parallel), ties and double or secondary standards (installed within 300mm of each primary standard) are generally required up at least one third of the scaffold height. Secondary standards can be attached to the ledgers of the scaffold with double couplers (R/A) or to the primary standards with swivels. Double standards or secondary standards help reduce the loads imposed on the primary standards.
4.7.2 Use of planks in erecting a platform or decks
A platform on a scaffold is to support workers and/or materials and plant. A platform can be made from a variety of materials such as: standard timber scaffold planks, prefabricated ply decks, aluminium grill decks, aluminium space or span decks, steel decks or planks.
For non proprietary scaffolds, the platform must be a minimum of:
Light duty: 675mm wide
Medium duty: 675mm wide
Heavy duty: 675mm wide
All scaffolds must maintain a clear and unobstructed access of not less than 450mm.
Planks or decking forming a platform should be of uniform thickness, slip resistant, pitched at an angle not exceeding 7 degrees to the horizontal (slope 1 to 8) and secured to prevent displacement in normal use and positioned to avoid significant gaps and trip hazards. Planks should be butted not lapped except at returns, curved faces or unusual profiles. Lapped planks other than returns, curved faces or unusual profiles, should be fitted with wedge cleats to reduce the risk of tripping. End overhang of planks must be 80mm minimum to 220mm maximum (see figure 34).
Figure 34: Butted planks
The securing of planks or decking against displacement is achieved by attaching them/it to the scaffold structure (putlog, transom, ledger, or rung etc). This can be done using:
- Lashing or similar.
- Wire.
- Steel or plastic strapping.
- Scaffold fittings.
- Spring loaded hook arrangements etc.
This significantly reduces gaps in working platforms and prevents planks lifting due to trap ends and wind uplift etc. Toeboards running across a working platform can also be used to secure the platform to prevent vertical uplift.
Ideally securing planks and decking will also prevent the unauthorised removal or movement of decking by the end user of the scaffold and at least automatically show if a plank or decking forming a platform has been moved between inspections.
Plank failure
Plank failure or breakage is a significant hazard in scaffolding. To reduce plank failure butt scaffold planks on a scaffold as opposed to lap planking the scaffold. For example on a light duty butt planked scaffold with 2.4m bays, three putlogs would support 1 x 3.0m long plank (maximum putlog spacing on a butt planked scaffold = 1.42m) but it is recommended that 1.2m be used. On a lap planked scaffold only 2 putlogs support the 3.0m long plank at 2.4m centres.
If a shock (impact) load was applied to a butt plank scaffold and the same shock (impact) load was applied to a lap plank scaffold the risk of a plank failure is significantly increased on a lap plank scaffold due to the greater putlog spacings.
4.7.3 Duty loadings on working platforms
The duty live loading for a scaffold is calculated as the maximum load permitted (men and materials) in any one scaffold bay.
4.7.3.1 Light duty working platforms
The maximum duty loading per bay permitted on a light duty scaffold is 225kg (2.2 kN).
The 225kg is calculated as a Uniformly Distributed Load (UDL) over the full bay. The maximum point load or concentrated load permitted is 100kg per bay as part of the maximum 225kg.
Additional requirements for a light duty working platform
Maximum standard spacing for light duty non proprietary scaffolds (see figure 35):
Longitudinal standard spacing - 2400mm (bay length).
Transverse standard spacing - 1575mm (bay width).
The minimum width of a working platform is 675mm for non proprietary scaffolds while maintaining unobstructed access of 450mm for all scaffolds.
The maximum number of working platforms useable concurrently in any one bay is:
Scaffold height up to 13.5m high - 4 lifts or working platforms per bay.
Scaffold height up to 33.0m high - 2 lifts or working platforms per bay.
Maximum putlog spacing is 2.4m
Figure 35: Light duty working platforms - maximum and minimum standard spacings
4.7.3.2 Medium duty working platforms
The maximum duty loading per bay permitted on a medium duty scaffold is 450kg (4.4 kN).
The 450kg is calculated as a Uniformly Distributed Load (UDL) over the full bay. The maximum point load or concentrated load permitted is 150kg per bay as part of the maximum 450kg.
Additional requirements for a medium duty working platform
Maximum standard spacing for medium duty non proprietary scaffolds (see figure 36):
Longitudinal standard spacing - 2400mm (bay length).
Transverse standard spacing - 1275mm (bay width).
The minimum width of a working platform is 675mm for non proprietary scaffolds while maintaining unobstructed access of 450mm for all scaffolds.
The maximum number of working platforms useable concurrently in any one bay is:
Scaffold height up to 13.5m high - 2 lifts or working platforms per bay.
Scaffold height up to 33.0m high - 1 lifts or working platforms per bay.
Maximum putlog spacing is 1.2m
Figure 36: Medium duty working platforms - maximum and minimum standard spacings
4.7.3.3 Heavy duty working platforms
The maximum duty loading per bay permitted on a heavy duty scaffold is 675kg (6.6 kN).
The 675kg is calculated as a Uniformly Distributed Load (UDL) over the full bay.
The maximum point load or concentrated load permitted is 200kg per bay as part of the maximum 675kg.
Additional requirements for a heavy duty working platform
Maximum standard spacing for heavy duty non proprietary scaffolds (see figure 37):
Longitudinal standard spacing - 1800mm (bay length).
Transverse standard spacing - 1275mm (bay width).
The minimum width of a working platform is 675mm for non proprietary scaffolds while maintaining unobstructed access of 450mm for all scaffolds.
The maximum number of working platforms useable concurrently in any one bay is:
Scaffold height up to 13.5m high - 2 lifts or working platforms per bay.
Scaffold height up to 33.0m high - 1 lifts or working platforms per bay.
Maximum putlog spacing is 0.9m
Figure 37: Heavy duty working platforms - maximum and minimum standard spacings
4.7.3.4 Special duty scaffolds
A special duty scaffold is a working platform that does not comply with the general requirements of a light, medium or heavy duty working platform with respect to loadings and/or dimensions. Special duty scaffolds should be notified to the DOL. There is a template for this in the appendix at the end of these guidelines.
Some examples of special duty scaffolds include:
- Bay widths that do not meet the minimum or maximum width requirements.
- Bay lengths that do not meet the minimum or maximum width requirements.
- Lift heights that do not meet the minimum or maximum height requirements.
- The exclusion of one or both guardrails.
- The exclusion of toeboards or kickboards.
- Vertical ladder on non proprietary scaffolds.
- Scaffolds with a gap greater than 300mm to the workface without inside guardrails.
- Limited access scaffolds.
- Concentrated weight scaffolds.
- Special duty loading platforms.
- Special duty cantilever scaffolds.
- Special duty hanging scaffolds.
- Special duty falsework (propping).
- Non proprietary scaffolds over 33.0m.
- Scaffolds erected from proprietary equipment that fall outside the manufacturer's specifications.
- Special duty bridging scaffolds.
- Special duty roof saddle scaffolds.
An example is if you require a single plank scaffold to access a restricted area between two buildings. The regulations require you to notify the scaffold as a special duty scaffold to the DOL stating the reason you cannot provide a minimum of 450mm clear access.
Additionally some special duty scaffolds require the design to be checked by a chartered engineer. For instance:
- Non proprietary scaffolds over 33.0m high.
- Scaffolds that exceed the maximum permitted height for proprietary scaffolds.
- Scaffolds using screening in very high wind areas.
- Scaffolds that require the supporting structure to be checked by a chartered engineer with regard to point loads, tie spacings etc.
- Scaffolds erected directly from a supporting structure, roof, verandah or balcony.
4.7.4 Permitted loads on scaffold tube
4.7.4.1 Galvanised steel tube 48.3mm outside diameter; 3.2mm wall thickness
Table 10 gives the loads that are permitted in New Zealand to be applied to galvanised steel scaffold tubes with 48.3mm OD x 3.2mm wall thickness complying with BS 6323.1. It takes into account a 15% reduction for reuse and the self-weight of the tube.
| Tube as a Beam | Tube as a Strut | |||||
|---|---|---|---|---|---|---|
| ClearSpan | Simply supported beam | Cantilevered beam | Strutlength | Concentric load | ||
| Point load | UDL | Point load | UDL | |||
| mm | kg | kg | kg | kg | mm | kg |
| 225 | 917 | 1835 | 229 | 459 | ||
| 300 | 687 | 1373 | 172 | 343 | 300 | 3870 |
| 450 | 456 | 914 | 114 | 228 | ||
| 600 | 343 | 684 | 86 | 171 | 600 | 3740 |
| 675 | 304 | 610 | ||||
| 900 | 230 | 456 | 900 | 3522 | ||
| 1125 | 181 | 363 | ||||
| 1200 | 170 | 341 | 1200 | 3190 | ||
| 1350 | 159 | 301 | ||||
| 1500 | 134 | 270 | 1500 | 2770 | ||
| 1575 | 128 | 254 | ||||
| 1800 | 110 | 221 | 1800 | 2275 | ||
| 2050 | 98 | 196 | ||||
| 2100 | 94 | 187 | 2100 | 1809 | ||
| 2250 | 88 | 173 | ||||
| 2400 | 82 | 162 | 2400 | 1442 | ||
| 2700 | 72 | 143 | 2700 | 1164 | ||
| 3000 | 64 | 127 | ||||
Notes
Cantilevered spans (beam) exceeding 600mm are not recommended.
UDL = Uniformly Distributed Load.
Example
The bold type above demonstrates the following using a clear span of 600mm:
- A 600mm tube simply supported at either end 600mm apart can sustain a maximum Safe Working Load (SWL) at one point (Point load) of 343kg and can support a maximum Uniformly Distributed Load (UDL) of 684kg.
- A 600mm tube cantilevered from a single support can sustain a maximum SWL at one point of 86kg and can support a maximum UDL of 171kg.
- A 600mm tube used as a strut or prop can sustain a load of 3740kg.
4.7.4.2 Aluminium scaffold tube 48.3mm outside diameter; 4.45mm wall thickness
Table 11 gives the loads that are permitted in New Zealand to be applied to aluminium scaffold tubes with 48.3mm OD x 4.45mm wall thickness complying with AS/NZS 1576.3. It takes into account a 15% reduction for reuse and the self-weight of the tube and limits the deflection of beams to 1/150 of the span.
| Tube as a Beam | Tube as a Strut | |||||
|---|---|---|---|---|---|---|
| ClearSpan | Simply supported beam | Cantilevered beam | Strutlength | Concentric load | ||
| Point load | UDL | Point Load | UDL | |||
| mm | kg | kg | kg | kg | mm | kg |
| 225 | 1633 | 3266 | 3229 | 354 | 225 | 6750 |
| 300 | 1224 | 2449 | 199 | 531 | 300 | 6527 |
| 450 | 816 | 1632 | 88 | 236 | 450 | 6082 |
| 600 | 612 | 1224 | 600 | 5637 | ||
| 675 | 544 | 1007 | 675 | 5414 | ||
| 900 | 354 | 566 | 900 | 4746 | ||
| 1125 | 226 | 361 | 1125 | 3595 | ||
| 1200 | 198 | 317 | 1200 | 3159 | ||
| 1350 | 156 | 250 | 1350 | 2496 | ||
| 1500 | 126 | 202 | 1500 | 2020 | ||
| 1575 | 114 | 183 | 1575 | 1834 | ||
| 1800 | 87 | 139 | 1800 | 1404 | ||
| 2050 | 68 | 109 | 2025 | 1109 | ||
| 2100 | 63 | 101 | 2100 | 1032 | ||
| 2250 | 55 | 88 | 2250 | 899 | ||
| 2400 | 48 | 76 | 2400 | 790 | ||
| 2700 | 37 | 59 | 2700 | 624 | ||
| 3000 | 29 | 47 | 3000 | 505 | ||
Notes
Cantilevered spans (beam) exceeding 450mm are not recommended.
UDL = Uniformly Distributed Load.
Example
The bold type above demonstrates the following using a clear span of 450mm:
- A 600mm aluminium tube simply supported at either end 450mm apart can sustain a maximum Safe Working Load (SWL) at one point (Point load) of 816kg and can support a maximum Uniformly Distributed Load (UDL) of 1632kg.
- A 450mm aluminium tube cantilevered from a single support can sustain a maximum SWL at one point of 88kg and can support a maximum UDL of 236kg.
- A 600mm aluminium tube used as a strut or prop can sustain a load of 6082kg.
4.7.5 Butt plank scaffold
When erecting a typical butt plank scaffold the base lift has putlogs connected with double couplers to the standard beneath the ledger. The ledger is connected to the standard with double couplers. The putlogs for butt planking are connected on top of the ledger with single couplers.
This allows for the base lift to have the ledgers connected to the standards and the putlogs under the ledgers to act as check clips. This provides additional strength in both the transverse and longitudinal plane via use of double couplers.
All additional lifts are erected with the ledger connected to the standard with double couplers and the putlogs for butt planking connected to the ledger with single couplers. A putlog must be within 300mm of the standards.
Figure 38 shows putlogs connected to the standards beneath the base ledgers. All the other putlogs are connected to the ledgers with singles.
Figure 38: Putlog positioning for butt plank scaffolds
4.7.6 Access to working platforms
Access to working platforms must be adequate and safe for the working conditions and type of work to be carried out. Especially consider the number of people using a scaffold and whether they need to carry materials or tools to the work platform. Some of the options for providing access to working platforms are outlined below.
4.7.6.1 Ladders
Depending on the application, ladders are traditionally made from aluminium, timber or fibreglass. In providing ladder access to working platforms:
- Ladders should be pitched at a slope of not less than 1 in 4 and not more than 1 in 6. Though it is not recommended, it is acceptable to have a pitched ladder stop at the working platform height if sufficient guardrails (stop ends) are in place that can be used to hold onto for access and egress to and from the ladder.
- If possible ladders should be securely tied to prevent movement top and bottom.
- Ladders should extend at least 1.0m above the working platform, landing or exit point.
- Ladders must be in good structural condition.
- The maximum height between working platforms or landings must not exceed 5.1m or a maximum of 2 lifts.
- Ladders must be offset to prevent a single continuous ladder. This reduces the distance a person could fall to a maximum of 5.1m (2 lifts).
- Where possible ladders should be erected in an independent scaffold bay. This is the preferred method, as it does not interfere with the working platform.
- All ladder access openings in a platform must be protected by either a hatch, gate or by tortured path.
Gaining and securing external ladder access
It is acceptable to secure a ladder to the outside of a scaffold from ground level to the 1st and 2nd lift (5.1m maximum working platform). This is usually achieved by extending a putlog to which the top of the ladder is then secured.
In terms of securing access from an external ladder, there are two options both involving the installation in the scaffold of an inward opening self closing gate or barrier. A prefabricated self closing gate may be installed at the lift height to allow and protect access. This is the preferred method of access for external ladders up to the second lift. Alternatively gaining access to working platforms from a ladder on the outside of the scaffold can be achieved by a short length of tube (approximately 1.2m) with swivel couplers to form a gate arrangement. You lift the gate to gain access to the working platform and put it back in place to maintain the guardrail to prevent falling from the working platform.
Prefabricated ladder gate arrangement
Figure 39 shows an external ladder used up to the second lift of a scaffold (5.1m maximum height) with a prefabricated self closing gate installed at the lift height to allow access. This is the preferred method of access for external ladders up to the second lift.
Figure 39: Prefabricated ladder gate
Swivel fitting ladder gate arrangement
Figure 40 shows an external ladder used up to the second lift of a scaffold (5.1m maximum height) with the top guardrail attached with a swivel fitting that can be raised to access the working platform and lowered to protect the working platform. This gate must also be self closing.
Figure 40: Swivel fitting ladder gate
Gaining and securing internal ladder access
Internal ladder access is acceptable if the ladder access hole is placed in part of the working platform and the minimum 675mm working platform width is maintained. Any hole or void in a working platform must either have adequate guardrails or a trapdoor arrangement must be used. This is to prevent stepping into the hole or void.
Vertical ladders should be avoided if possible. They can be used on a special duty scaffold if access is restricted, such as in a tank or ducting. Guardrailing or trapdoor systems must be used in conjunction with vertical ladders.
Ladder hatch arrangement
Figure 41 shows a ladder protruding through a working platform with a hatch arrangement to ensure that no void is left in a working platform. It may be necessary to support the outside of the hatch if the hatch does not have an outside plank to support it. A single coupler can be attached to the outside ledger to accomplish this. The hinge arrangements can be standard hinges or heavy duty carpet or similar. It is recommended that the hatch be lapped a minimum of 32mm onto the adjacent planks.
Figure 41: Internal ladder hatch
Tortured path
Above the second lift of a scaffold all ladders must be erected within the framework of the scaffold or in a dedicated ladder access bay. The opening to the work platform can be protected by the ladder hatch arrangement as shown in figure 41. For a dedicated ladder access bay creating a barrier that a person must walk around to access the ladder opening is called a tortured path. This can easily be erected using tube and fittings or proprietary components. The objective is to prevent a person stepping back from a platform into the ladder opening (see figure 42).
Figure 42: Tortured path method for constructing ladder access bays
4.7.6.2 Stairs
Traditionally stairs are made from aluminium, timber or steel. They usually come in a 'stair unit' comprised of a number of stairs.
Stair units are usually attached to a scaffold by hooking over a tube or by sitting in a transom on a system type scaffold. Other connecting methods, while used, are not as common. Stairs are usually placed in a separate bay against a working platform. Sloping guardrails must be used to give something to hold onto when ascending or descending the stairs.
Stairs generally come in 1.5m lifts as they can be fitted within a 2.4m long bay maintaining the correct step dimensions and landing dimensions to turn around on. Because 1.5m rise stairs do not match normal scaffold lifts it may be necessary to provide a stepping platform from the working platform to the stairs.
Stair units that come in 2.0m lifts must either use a bay length of greater than 2.4m or the landings must be extended or cantilevered from the 2.4m bay.
Stairs can be made up using stair brackets, planks and tubes. While this is acceptable, structures must be checked to ensure all steps are level, secure from movement, and can take the live loads imposed - like a 100kg man running down the stairs! Using ply from the front edge of the top step to the back edge of the lower step forms a complete unit that will prevent the step from rotating forward or backwards.
Access from a stair unit to the work platform must be maintained like a ladder access. A guardrail or gate arrangement must be kept in place to prevent people walking from a working platform into a stair opening.
Figure 43 shows a proprietary aluminium mobile stair access tower.
Figure 43: Proprietary mobile stair access tower
Figure 44 shows both a typical external ladder access tower and an external stair access tower attached to the same scaffold. Each forms a separate access bay.
Figure 44: Combined ladder and
stair access
Footnotes
[3] This is the preferred tie method in most circumstances
