Scaffold trigger versus edge trigger
Scaffolds have their own fall protection trigger. 29 CFR 1926.451(g)(1) requires fall protection for scaffold workers more than 10 ft above a lower level. Subpart M's 6 ft trigger does not apply to scaffolds.
Residential construction at an unprotected side or edge is different: 1926.501(b)(13) requires guardrails, safety nets or personal fall arrest at 6 ft or more.
Worked case: a worker on a supported scaffold 9 ft up and a framer at an unprotected second-floor edge 9 ft up. The edge worker is over 6 ft and must be protected. The scaffold worker is under the 10 ft scaffold trigger and is not required to be. Trap: protecting both applies the 6 ft edge trigger to the scaffold, the common error. Protecting only the scaffold worker reverses the two rules.
Scaffold toprail height
Scaffold toprails are not built to the 42 ± 3 in guardrail figure. 1926.451(g)(4)(ii) sets two ranges for supported scaffolds, based on when the scaffold was manufactured or placed in service:
- Before January 1, 2000: 36 to 45 in above the platform.
- After January 1, 2000: 38 to 45 in.
Trap: a 1995 scaffold gets the older 36 to 45 in range, not 38 to 45 in. The 39 to 45 in range is the Subpart M guardrail (42 ± 3 in), which does not govern scaffold toprails, and "42 in exactly" ignores the allowed range entirely.
Capacity: the 4x rule
1926.451(a)(1) requires each scaffold and scaffold component to support its own weight plus at least 4 times the maximum intended load.
Worked case: a plank with a 750 lb maximum intended load must support 750 × 4 = 3,000 lb plus its own weight.
Traps from neighboring factors:
- 6 times is for suspension ropes and their connecting hardware (1926.451(a)(3) to (a)(4)); 750 × 6 = 4,500 lb is wrong for a plank.
- 3.3 times is the extra-heavy-duty Type 1A ladder factor (1926.1053).
- 2 is the safety factor for a qualified person's personal fall arrest system (1926.502(d)(15)).