Scaffold General Requirements – 1926.451(c) Criteria for Supported Scaffolds

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.

Image result for supported scaffolds. Size: 145 x 160. Source:

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.

Platform – 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 define 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 general 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.