Scaffold Guardrail System Check (OSHA 1926.451(g)(4))
The guardrail scaffold-takeoff says is taken off separately, and two things make it more than a tape check.
Example
You enter
- Top rail height above the platform (in) 42
- Midrail height above the platform (in; 0 to skip) 21
- Toeboard height (in; 0 = none) 4
- Top rail capacity (lbf; 0 to skip) 200
- Midrail capacity (lbf; 0 to skip) 150
- Scaffold type other
- Band used for 'approximately midway' (in) 3
You get
- Midrail target (in) 21
- Midrail offset (in) 0
- Required toprail (lb) 200
- Required midrail (lb) 150
Checked against published worked examples from: Occupational Safety and Health Administration.
Details, formula, and sources
ScopeThe midrail is specified by RELATION, not a number -- approximately midway between the top edge and the platform -- so the target MOVES with the top rail, and a shop standard set for a 45 in rail sits 3.5 in high under a 38 in one. And the capacities are PAIRED: 200 lbf on the top rail for scaffolds generally, 100 lbf for single- and two-point adjustable suspension, and 150 lbf on the midrail where the top rail carries 200, 75 lbf where it carries 100. Top edge 38 to 45 in, and never under 36. Toeboard at least 3.5 in from its top edge to the walking surface -- though WHETHER one is required is falling-object protection under 1926.451(h) and a different question. OSHA is public domain, so the values are quoted.
Formula or tabletop rail passes at 38 in <= height <= 45 in; the midrail target is top rail height / 2, tested against a user-set band because the standard says approximately midway; required top rail capacity is 200 lbf for all other scaffolds and 100 lbf for single- and two-point adjustable suspension scaffolds; the midrail capacity is 150 lbf where the top rail requirement is 200 lbf and 75 lbf where it is 100 lbf; toeboard height >= 3.5 in.
Source and editionOSHA 29 CFR 1926.451(g)(4), Subpart L - Scaffolds. A US federal regulation in the public domain, so the values are quoted directly rather than paraphrased.
Free access29 CFR is published in full at no cost by OSHA and the eCFR. Nothing here is licensed.
What governsEstimate. AHJ and licensed professional govern.
API field namestop_rail_height_in, midrail_height_in, toeboard_height_in, toprail_capacity_lb, midrail_capacity_lb, scaffold_type, midrail_tolerance_in, midrail_target_in, midrail_offset_in, required_toprail_lb, required_midrail_lb
- Top edge height 38 to 45 in for scaffolds placed in service after 2000; never under 36 in29 CFR 1926.451(g)(4)
- Midrail approximately midway - a moving target, tested against a user-set band29 CFR 1926.451(g)(4)
- Top rail capacity 200 lbf generally; 100 lbf for single- and two-point adjustable suspension29 CFR 1926.451(g)(4)
- Midrail capacity 150 lbf where the top rail requirement is 200 lbf; 75 lbf where it is 100 lbf29 CFR 1926.451(g)(4)
- Toeboard height at least 3.5 in from its top edge to the walking/working surface29 CFR 1926.451(g)(4)
- Toeboard trigger falling-object protection under 1926.451(h) - not determined herestated scope limit