1926.451(c) Criteria Supported

Supported scaffolds consist of one or more platforms supported by outrigger beams, brackets, poles, legs, uprights, posts, frames, or similar rigid support. Requirements differ depending on the type being used. The structural members: poles, legs, posts, frames, and uprights must be plumb and braced to prevent swaying and displacement.

  • Supported scaffolds with a height to base width ratio of more than 4:1 must be restrained by guying, tying, bracing, or an equivalent means.
  • Follow the manufacturers’ recommendation or the following placements must be used for guys, ties, and braces.
  • Install guys, ties, or braces at the closest horizontal member to the 4:1 height and repeat vertically with the top restraint no further than the 4:1 height from the top.
  • Vertically – every 20 feet (6.1 m) or less for scaffolds less than 3 feet (0.91 m) wide; every 26 feet (7.9 m) or less for scaffolds more than 3 feet (0.91 m) wide.
  • Horizontally – at each end; at intervals not to exceed 30 feet (9.1 m) from one end.
  • Supported scaffolds’ poles, legs, posts, frames, and uprights must bear on base plates and mud sills, or other adequate firm foundation.
  • Except when used only as a walkway, the platform is the work area of the scaffold. Therefore, an inspection of a scaffold platform requires safety checks of both the platform structure and how the platform is used by the workers. The work at height regulations defines a working platform as any platform used as a place of work or as a means of access to or egress from a place of work, including any scaffold, suspended scaffold, cradle, mobile platform, trestle, gangway, gantry and stairway that is so used.
  • Keeping Upright – Once a scaffold is built, even if it is compliant with every other standard relating to footings, structure, capacity, etc., it still will not provide a safe work platform if it does not remain upright. As a rule, a scaffold becomes inherently unstable once its height is four times its minimum base dimension, even if it is plumb and square. Extreme weather or damage to structural components can also affect a scaffold’s stability.

Electrical Hazards

Because they may be built in proximity to overhead power lines, and because they are often made of metal, scaffolds can put workers at risk of electrocution. This risk can be removed through proper clearance and maintenance.

Forklifts can support platforms only when the entire platform is attached to the fork and the fork-lift does not move horizontally when workers are on the platform.

Front-end loaders and similar equipment can support scaffold platforms only when they’ve been specifically designed by the manufacturer for such use.

Specific Requirements for Supported Scaffolds

  • When platforms are being moved to the next level, the existing platform must be left undisturbed until the new bearers have been set in place and braced before receiving the new platform.
  • Couplers must be made of a structural metal, such as Drop-forged steel, malleable iron or structural-grade aluminum.
  • The use of couplers made from gray cast iron is prohibited.
  • Tube and coupler scaffolds over 125 feet in height must be designed by a registered professional engineer. They also must be constructed and loaded in accordance with that design.

Specific Requirements for Supported Scaffolds

  • Transverse bracing forming an “X” across the width of the scaffold must be installed at the scaffold ends, and at least at every fourth runner vertically.
  • Bracing must extend upward diagonally to opposite sides of the scaffold, such as from the inner posts or runners to the next outer posts or runners, or vice versa.
  • Building ties must be installed at the bearer levels between the transverse bracing.
  • Meet the requirements of on straight run scaffolds, longitudinal bracing across the inner and outer rows of posts must be installed diagonally in both directions.
  • Extend upward from the base of the end posts to the top of the scaffold at approximately a 45-degree angle.
  • On scaffolds whose length is greater than their height, longitudinal bracing must be repeated beginning at least at every fifth post.
  • On scaffolds whose length is less than their height, longitudinal bracing must be installed from the base of the end posts upward to the opposite end posts, and then in alternating directions until reaching the top of the scaffold.
  • Bracing must be installed as close as possible to the intersection of the bearer and post or runner and post where conditions do not permit the attachment of bracing to posts, bracing must be attached to the runners as close to the post as braces, bearers and runners.
  • Cross bracing must be installed between the inner and outer sets of poles on double pole scaffolds.
  • Diagonal bracing must be installed in both directions across with the entire outside face of double- and single-pole scaffolds.  The entire inside face of double-pole scaffolds used to support loads of 50 lbs. or more per square foot.
  • Runners and bearers must be installed on edge.
  • Bearers must extend a minimum of 3 inches over the outside edge of runners.
  • Runners must extend over two poles at minimum.
  • Be supported by bearing blocks securely attached to the poles.
  • Braces, bearers, and runners must not be spliced between poles.
  • Bearers must be installed transversely between posts.
  • When bearers are coupled to posts, the inboard coupler must bear directly on the runner coupler and be as close to the posts as possible.
  • Bearers must extend beyond the posts and runners and provide full contact with the coupler.
  • The bottom bearers must be located as close to the base as possible.

Specific Requirements for Runners

  • Runners must be installed along the length of the scaffold, located at level heights on both the inside and outside post.
  • On outside posts, tube and coupler guardrails and mid-rails may be used in lieu of outside runners.
  • Runners on straight runs must be Interlocked to form continuous lengths.
    Coupled to each post.
  • The bottom runners must be located as close to the base as possible.