Three multi-story limits in 1926.754(b)
29 CFR 1926.754(b) sets three limits candidates swap:
- (b)(1): no more than 8 stories between the erection floor and the uppermost permanent floor, unless the design maintains structural integrity.
- (b)(2): no more than 4 floors or 48 ft (14.6 m), whichever is less, of unfinished bolting or welding above the foundation or uppermost permanently secured floor.
- (b)(3): a fully planked or decked floor, or nets, kept within 2 stories or 30 ft (9.1 m), whichever is less, directly under any erection work.
8 stories is not the unfinished-bolting limit.
Work the whichever-is-less math
For (b)(2) and (b)(3), multiply the stories by the floor height, then take the smaller figure.
- 14 ft floors, (b)(2): 4 × 14 = 56 ft. 48 ft is less, so 48 ft governs. 56 ft skips the comparison; 112 ft (8 × 14) wrongly applies the 8-story rule.
- 12 ft floors, (b)(3): 2 × 12 = 24 ft. 24 ft is less than 30 ft, so 24 ft governs. Answering 30 ft ignores the comparison; 48 ft is (b)(2); 15 ft is the fall-protection trigger in 1926.760(a)(1).
Perimeter columns: 48 in
Under 1926.756(e), unless constructibility does not allow it, a perimeter column may not be erected unless it extends at least 48 in (1.2 m) above the finished floor, so perimeter safety cables can be attached. It must also have holes or devices for the cables at 42 to 45 in above the finished floor and at the midpoint between the floor and the top cable.
The trap: 42 in is the low end of the top-cable hole height, not the column extension, and 18 in is the offset for the 300 lb eccentric load in 1926.755(a)(2).
Opening covers: twice the weight
Under 1926.754(e)(3), roof and floor opening covers must support, without failure, twice the weight of the employees, equipment and materials that may be on them at any one time. They must be secured against displacement and painted with high-visibility paint or marked HOLE or COVER. Just the expected weight leaves no margin.