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WCB Standards

WCB Standard: WPL 1-2004 Design, Construction and Use of Wood Frame Scaffolds

© Workers' Compensation Board of British Columbia. All rights reserved. No part of this document may be copied, reproduced, or distributed for profit or other commercial enterprise, nor may any part be incorporated into any other publication, without written permission of the Workers' Compensation Board of B.C.

1. Scope
This Standard applies to the design, construction, use, and maintenance of job constructed wood frame scaffolds.

This Standard does not cover shore or lean-to scaffolds.

2. Definitions

"building tie" means a connection between a standing scaffold and a permanent structure;

"double-pole scaffold" means a scaffold with both ends of the bearers supported by connections to posts or uprights;

"guardrail" means a guard consisting of a top rail 102 cm to 112 cm (40 in to 44 in) above the work surface, and an intermediate rail located approximately midway between the underside of the top rail and the top of the toeboard, if one is provided, or the work surface if no toeboard is provided;

"heavy duty" means intended to support both workers and stored or stacked materials, such as bricks and masonry;

"light duty" means intended to support workers, their personal hand tools and material for immediate use only;

"running scaffold" means a double-pole scaffold comprised of 2 or more bays;

"scaffold or scaffolding" means any temporary work platform and its supporting structure used for supporting workers, or materials, or both;

"single-pole scaffold" means a scaffold with the outer ends of the bearers supported on ledgers secured to a single row of posts or uprights, and the inner ends of the bearers supported on or in a wall;

"toeboard" means a guard with a top at least 10 cm (4 in) above the floor or platform, and the space between the bottom of the toeboard and the floor or platform not exceeding 13 mm (1/2 in);

"work platform" means an elevated or suspended temporary work base for workers.

3. Responsibilities
  1. Employers must ensure that scaffolds used by their workers are in safe condition, regardless of who erected the scaffolds.
  2. A scaffold must be erected, altered and dismantled by, or under the direct supervision of, qualified workers.
  3. A scaffold must be inspected daily before use and after any modification.
  4. A damaged scaffold component must not be used until it has been effectively repaired.
4. Lumber for structural components
  1. Unless otherwise specified in this Standard, lumber used to construct scaffolding must be graded Number 2 or better Douglas fir-larch, hemlock-fir, spruce-pine-fir or coast-Sitka-spruce.
  2. All lumber must be graded and marked to the National Lumber Grades Authority Standard Grading Rules for Canadian Lumber or other grading rules acceptable to the board.
5. Scaffold stability
  1. A scaffold must be erected with vertical members plumb and ledgers and bearers level.
  2. The lower end of the vertical support of a scaffold must be supported by firm and adequately sized foundations or sills.
  3. The poles, legs and uprights of a scaffold must be securely and rigidly braced to prevent swaying and displacement.
  4. A scaffold must be effectively guyed or secured to a building or structure if the height of the scaffold exceeds 3 times its minimum base dimension.
  5. If building ties or guys are used
    • (a) the first level of ties or guys must be placed at a height not exceeding 3 times the scaffold minimum base dimension, and additional building ties or guys placed at vertical intervals not exceeding 6 m (20 ft), and

      (b) building ties or guys must be placed at longitudinal intervals of every third bay or 6.4 m (21 ft), whichever is less, and at each end of the scaffold.
  6. Each building tie must be capable of resisting a working load of 4 kN (900 lbs), applied horizontally and perpendicular to the structure, or a proportionately equivalent load where ties are spaced closer together or guying is employed.
  7. If a scaffold is enclosed by a tarp or other cover for protection against climatic conditions, bracing for the scaffold must be installed in accordance with the instructions of a professional engineer to meet design criteria for wind or other weather induced loads that may be imposed.

Note: For the purpose of compliance with subsection (2), if changing weather conditions may cause freezing or thawing of the ground or other surface supporting a scaffold, adequate precautions need to be taken to ensure the continued suitability of the supporting surface. For compliance with subsection (6), CSA Standard CAN/CSA-S269.2-M87, Access Scaffolding for Construction Purposes, provides some examples of typical details for building ties.

6. Guardrails and toeboards
  1. Except as provided by subsections (2) and (5), a work platform 3 m (10 ft) or more above grade or floor level must have guardrails on all open sides and ends.
  2. If an edge of the work platform is adjacent to a structure that provides equivalent protection to guardrails, then guardrails may be omitted on that edge and there may be an open space between the work platform and the structure of up to 30 cm (12 in).
  3. Toeboards must be provided if there is a danger from tools, materials, equipment and debris falling off the edge of the work surface, or there is a danger of slipping off the work surface due to the environment or work practices being used.
  4. If material is stacked or stored on a platform or walkway, or near a floor opening, toeboards must be increased in height or solid or mesh panels of appropriate height must be installed to prevent the material from falling.
  5. Subsections (1) and (3) do not apply to a walkway or a platform that is on a performance stage or scenic unit and will be visible to the audience during a rehearsal or performance, provided that effective measures are taken to protect performers and other workers from injury.

Dimensions for guardrails are shown in Tables 1 and 2. Sample guardrails are shown in Figure 1.

Figure 1 - Single Pole Wood Scaffold (Light Duty)

Dimensions for light duty single pole wood scaffold

7. Lumber planks
  1. Except as provided elsewhere in this Standard, solid wood scaffold planks used as work platforms must be cut from Douglas fir-larch, hemlock-fir, spruce-pine-fir or coast-Sitka-spruce species, and

    (a) for a maximum span of 3 m (10 ft), must be

    (i) graded "Select Structural - Scaffold Plank" not less than 38 mm x 235 mm (2 in x 10 in nominal),

    (ii) graded "Select Structural - Joists and Planks" not less than 38 mm x 235 mm (2 in x 10 in nominal),

    (iii) graded "No. 2 and Better - Joists and Planks", not less than 48 mm x 251 mm (2 in x 10 in rough sawn), or

    (iv) graded "No. 2 and Better - Joists and Planks", not less than 38 mm x 235 mm (2 in x 10 in nominal), provided the planks are doubled (one on top of the other), or

    (b) for a maximum span of 1.8 m (6 ft) and light-duty work only, must be graded "No. 2 and Better - Joists and Planks", not less than 38 mm x 235 mm (2 in x 10 in nominal).
  2. Any lumber graded in accordance with subsection (1)(a)(ii), (iii), (iv), or (b) must be hand picked for minimal knots and straight grain to ensure that it is suitable for use as a scaffold plank.
  3. Each lumber scaffold plank must

    (a) be visually inspected for defects before each installation and not used if found to be defective,

    (b) except as noted in subsection 1(b), be supported at intervals not exceeding 3 m (10 ft) for lightduty activity and 2.1 m (7 ft) for heavyduty activity,

    (c) have its ends extend not less than 15 cm (6 in) and not more than 30 cm (12 in) beyond the supporting member, and

    (d) for light duty activity, support no more than one worker unless it is connected to the adjoining plank.
  4. (4) A work platform must

    (a) consist of lumber or manufactured scaffold planks placed side by side to provide a work surface with a minimum nominal width of 50 cm (20 in), except that a nominal 30 cm (12 in) wide work platform is acceptable for use with ladder jacks, and

    (b) as far as possible, completely cover the area between front and rear vertical supports or the rear guardrail, and in no case leave more than one opening in the work platform area, and the opening must be no greater than 25 cm (10 in) in width.
8. Manufactured planks
  1. A manufactured scaffold plank must meet the requirements of

    (a) CSA Standard CAN/CSA S269.2-M87, Access Scaffolding for Construction Purposes,

    (b) ANSI Standard A10.8-1988, American National Standard for Construction and Demolition Operations - Scaffolding - Safety Requirements,

    (c) ANSI Standard A14.7-1991, Safety Requirements for Mobile Ladder Stands and Mobile Ladder Stand Platforms,

    (d) CSA Standard CAN3-Z271-M84, Safety Code for Suspended Powered Platforms, or

    (e) the written requirements of a professional engineer.
  2. A manufactured scaffold plank must be used in accordance with the manufacturer's instructions and limitations, except as provided in subsection (3).
  3. A scaffold plank fabricated at the jobsite must be made to a design certified by a professional engineer to meet the requirements of CSA Standard CAN/CSA-S269.2 M-87, Access Scaffolding for Construction Purposes, and a copy of the design must be available on site.
9. Securing planks

Each lumber and manufactured scaffold plank installed for use must be secured against dislodgement.

10. Sloping platforms

A work platform which slopes from one end to the other must be

(a) sloped not more than 1 vertical to 5 horizontal, and

(b) fitted with cleats on its upper surface, at not more than 40 cm (16 in) intervals or other equally effective measures must be used to ensure adequate footing for workers using the platform.

11. Access to scaffolds
  1. Access to otherwise inaccessible working levels of a scaffold up to 9 m (30 ft) above a floor or grade must be provided by a vertical or portable ladder, or stairway, attached to the scaffold.

  2. Access to otherwise inaccessible working levels of a scaffold over 9 m (30 ft) above a floor or grade must be provided by

    (a) a stairway erected for the full height of the scaffold,

    (b) a temporary passenger hoist approved for use under the Elevating Devices Safety Regulation,

    (c) an attached vertical ladder, with rest platforms at least every 9 m (30 ft) which are fully guarded except at the ladder location, or
  3. A worker must not climb scaffold members between landings.
12. Vertical ladders
  1. A vertical ladder providing access to working levels of a scaffold must

    (a) be adequately fastened to the scaffold,

    (b) be configured so that its siderails extend approximately 1 m (3 ft) above the working level,

    (c) have rungs spaced at 30 cm (12 in) on centre, and

    (d) have a clear space of at least 15 cm (6 in) behind each rung.
  2. A ladder attached to a scaffold must be positioned so that its use will not cause the scaffold to become unstable.
13. Spacing of components

The horizontal spacing between uprights, guardrail posts and bearers in a wood scaffold must not exceed

    (a) 3 m (10 ft) for a light duty scaffold, and

    (b) 2 m (7 ft) for a heavy duty scaffold.
14. Bracing of uprights

Adjacent uprights must be connected with horizontal runners (ledgers and bearers) to ensure that the unbraced vertical length of an upright does not exceed 2.4 m (8 ft).

15. Cross bracing

A scaffold must be adequately supported in two directions by a system of diagonal cross braces secured to the uprights as close to the ledgers as possible.

16. Single-pole components

Components of a light duty single-pole wood scaffold must have minimum nominal dimensions conforming to Table 1 and grade and species in accordance with section 4.

17. Double-pole components

Components of a double-pole wood scaffold must have minimum nominal dimensions conforming to Table 2 and grade and species in accordance with section 4.

A sample sketch of a light duty double pole scaffold is shown in Figure 2.

Table 1: Single-pole scaffolds
Component Nominal dimensions (inches)1
Uprights - up to 6 m (20 ft) 2 x 4
- 6 m to 15 m (20 ft to 50 ft) 4 x 4
Bearers - 90 cm (3 ft) maximum span 1 x 6
- 1.5 m (5 ft) maximum span 2 x 6
Ledgers 1 x 6 or 2 x 4
Braces 1 x 6 or 2 x 4
Wall scabs and bearer blocks 2 x 6
Guardrails (top rail) 2 x 4 (up to 2.4 m (8 ft) span)
2 x 6 (2.4 m - 3 m (8 ft - 10 ft) span)
Guardrails (intermediate rail) 2 x 4
Toeboards 1 x 4
Scaffold planks As required by section 7 or 8

Table 2: Double-pole scaffolds
  Nominal dimensions (inches)1
Component Light duty Heavy duty
Uprights - up to 6 m (20 ft) 2 x 4 2 x 6
- 6 m to 15 m (20 ft to 50 ft) 4 x 4 4 x 6
Bearers - 1.5 m (5 ft) max. span 2 - 1 x 6 or
1 - 2 x 6
2 - 2 x 6 or
1 - 2 x 10
Ledgers 1 x 6 or 2 x 4 1 x 6 or 2 x 4
Braces 1 x 6 or 2 x 4 1 x 6 or 2 x 4
Guardrails (top rail) 2 x 4 (up to 2.4 m (8 ft) span)
2 x 6 (2.4 m - 3 m (8 ft - 10 ft) span)
2 x 4
Guardrails (intermediate rail) 2 x 4 2 x 4
Toeboards 1 x 4 1 x 4
Scaffold planks As required by section 7 or 8 As required by section 7 or 8

1 In Tables 1 and 2 dimensions are nominal sizes for surfaced dry lumber and have actual dimensions in millimetres as follows: 2 x 4 is 38 mm x 89 mm, 4 x 4 is 89 mm x 89 mm, 4 x 6 is 89 mm x 140 mm, 1 x 6 is 19 mm x 140 mm, 2 x 6 is 38 mm x 140 mm and 2 x 10 is 38 mm x 235 mm.

Dimensions for light duty double-pole scaffold
18. Extension of uprights
  1. A wood upright may only be extended using a butt joint, strengthened by two wooden splice plates not less than 1.2 m (4 ft) long.
  2. The splice plates for wood uprights must have a minimum thickness of 38 mm (2 in nominal) and must have the same width as the spliced members.
  3. The combined cross-sectional area of the splice plates must be at least that of the vertical upright member.
19. Laminated uprights

When wood uprights are fabricated by the lamination of two or more pieces of material to obtain the required cross-sectional dimensions, the distance between joints must be at least 1.2 m (4 ft). A sample laminated upright is shown in Figure 3.

20. Bearer supports
  1. The inner ends of bearers on single-pole scaffolds must be supported by bearer blocks, and securely fastened to wall scabs.
  2. Manufactured bearer supports must be of a design acceptable to the board, and be secured to solid wall materials.
  3. Bearer hooks which engage holes in the wall sheathing must be adequately supported by stiffeners secured to wood studs or blocking.

Note: Sample bearer connections are shown in Figure 3.

Figure 3 - Bearer Connections At Wall and Laminated Upright, Single Pole Scaffold

Bearer connections at wall and laminated upright for single-pole scaffold

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