OSHA Guardrail Wood Grading

emart0429 · Mar 14, 2025

Sorry if this has been asked and answered before, but I'm not finding it in any searches. I'm looking at fall protection requirements in OSHA Part 1926 and run into an appendix B which lists wood, pipe, and steel rail sections OSHA says meets their requirements for guardrail. Here's a link to the sections: 1926 Subpart M App B

The question I have is on the requirements for the wood members. It lists a 1500 lb-ft/in2 construction grade lumber. Here's a quote from App B, "Wood components shall be minimum 1500 lb-ft/in2 fiber (stress grade) construction grade lumber; the posts shall be at least 2-inch by 4-inch (5 cm × 10 cm) lumber spaced not more than 8 feet (2.4 m) apart on centers; the top rail shall be at least 2-inch by 4-inch (5 cm × 10 cm) lumber."

What is "1500 lb-ft/in2 construction grade lumber?" Construction Grade DF-L or HF (most popular materials around here) only have a Fb value of around 1000 lb/in2 which makes me wonder why OSHA has the units listed as lb-ft/in2?

Anybody have any experience with this?

Thanks,
Erik

SWComposites · Mar 14, 2025

emart0429 said:
lb-ft/in2

is probably referring to a bending capability rather than a stress value. but yeah, weird units.

ANE91 · Mar 14, 2025

Here’s a guess while you wait for someone with the knowledge:

I don’t see a single species with construction grade F_b greater than 1,500 psi. That’s the first clue. They’re likely referring to adjusted design values (F’_b), not reference design values (F_b). Moreover, OSHA doesn’t care if you spring for Select Structural over Construction. Why would they?

fel3 · Mar 14, 2025

"lb-ft" may be a corruption of "lbf" for pound-force, which is the numerator in psi.

emart0429 · Mar 17, 2025

Thanks for the feedback everyone. Seems like we're all on the same page and all questioning exactly what OSHA is referring to. Glad I'm not just missing the boat somehow.

I guess the other item I could argue to justify the "high" 1500 psi (assuming that's what they meant) reference would be that I would typically treat OSHA loads as strength level loading instead of ASD. So, by the time you add the adjustment factors to bump up from ASD wood stresses to LRFD wood stresses it wouldn't be that difficult to find a 1500 psi minimum rated material.

Anyway, thanks again for the input.

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