OSHA 1926.451(c)(2): scaffold footing, base plates and mud sills
Under 29 CFR 1926.451(c)(2), supported scaffold poles, legs, frames and uprights must bear on base plates and mud sills or another adequate firm foundation. Footings must be level, sound, rigid and able to carry the loaded scaffold without settling, and unstable objects may not be used as supports.
Official text
(c)(2) Supported scaffold poles, legs, posts, frames, and uprights shall bear on base plates and mud sills or other adequate firm foundation. (i) Footings shall be level, sound, rigid, and capable of supporting the loaded scaffold without settling or displacement. (ii) Unstable objects shall not be used to support scaffolds or platform units. (iii) Unstable objects shall not be used as working platforms. (iv) Front-end loaders and similar pieces of equipment shall not be used to support scaffold platforms unless they have been specifically designed by the manufacturer for such use. (v) Fork-lifts shall not be used to support scaffold platforms unless the entire platform is attached to the fork and the fork-lift is not moved horizontally while the platform is occupied.Read the full section on eCFR
(c)(3) Supported scaffold poles, legs, posts, frames, and uprights shall be plumb and braced to prevent swaying and displacement.Read the full section on eCFR
(f)(3) Scaffolds and scaffold components shall be inspected for visible defects by a competent person before each work shift, and after any occurrence which could affect a scaffold's structural integrity.Read the full section on eCFR
What it requires, in plain English
- Each leg, post, frame or upright bears on a base plate and mud sill or other adequate firm foundation.
- Footings are level, sound, rigid and capable of supporting the loaded scaffold without settling or displacement.
- Unstable objects are not used to support scaffolds or platform units, or as working platforms.
- Poles, legs, frames and uprights are plumb and braced to prevent swaying and displacement.
Where it shows up on site
- Frame legs set on concrete blocks, bricks or stacked lumber
- Base plates sitting directly on soft or freshly backfilled soil with no mud sill
- Mud sills that have washed out or settled after rain
Verify on site before you call it
A photo rarely shows every fact a standard depends on. Confirm these in person before treating the condition as a violation:
- Is the scaffold a supported scaffold bearing on the ground or a lower surface?
- What is under the base plates outside the photo: mud sills, slab, or soil?
- Has the ground been disturbed, backfilled or wetted since erection?
- Are the legs plumb, or has any leg settled?
Typical corrective actions
- Clear the scaffold until a competent person checks the footing.
- Replace blocks, bricks or other unstable supports with base plates on mud sills or another firm foundation.
- Re-level and plumb the scaffold, and brace it against sway and displacement.
- Re-inspect the footing after rain, excavation nearby, or any event that could cause settling.
Common questions
Can you set a scaffold on concrete blocks?
1926.451(c)(2)(ii) states that unstable objects shall not be used to support scaffolds or platform units. Legs must bear on base plates and mud sills or another adequate firm foundation that will not settle or shift under the loaded scaffold.
Are mud sills required under every scaffold?
The rule requires base plates and mud sills or other adequate firm foundation. Where the scaffold bears on a surface that is already level, sound and rigid, that surface can serve as the firm foundation, provided the footing meets (c)(2)(i).
Turn the observation into a notice
Record what the photo shows, confirm the on-site checks above, and identify the responsible company and due date. Use the fillable construction safety notice template or follow aworked example from observation to verified fix. Cirqify can draft the notice from your circled photo for you to review.
Related standards
This guide summarizes federal OSHA construction standards for general information. It is not legal advice. States with their own OSHA-approved plans may set different or additional requirements; see federal and state coverage.