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Brian, Architect
Category: Home Improvement
Satisfied Customers: 3123
Experience:  Licensed Architect- 17 years, L.E.E.D. AP
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how to build a stairwell using floor trusses and location ...

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how to build a stairwell using floor trusses and location and quanity of support posts for stairwell parrallel to trusses adjacent to foundation wall diagrahm helpful


Welcome to Just Answer.

Regardless of where the stair is located, you need to use conventional framing for the stair opening. 1-3/4"x "depth of floor" LVL's would be best at framing the opening, since they are stronger than the typical 2x's; they should span the same length as the the truss joist when running in the same direction. The joists parallel to the stair should be doubled and so should the headers. Everything should be held together with metal joist/ beam hangers and the truss joists can end at the headers, to be held up with metal hangers. No posts are needed. Here is an example of a framed stair opening, except I would use doubles around the entire perimeter, and these would be solid wood. The rest of the framing would be the open trusses.


If you need further help or clarification on this question, please reply to this post.

Best of Luck, Brian


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Customer: replied 9 years ago.
thanks for replying. my trusses will span 32 feet 16" o.c. the trusses are 24" deep. i've gotten different answers from different truss plants about this question. will lvl come 24" deep and is that safe to span 32' without columns at stairwell.(one side is adjacent to foundation and opening is 6 ft back from front of foundation, opening 40"x14', then another 12 ft behind stairwell to back of foundation. (using lvl you mean this part of plan is independent from trusses?(not connected to them at all) also is 3/4" osb subfloor nailed and glued ok on these 24" trusses 16" o.c. thanks alot

Sorry, I didn't realize that the trusses were spanning 32 feet and that they are 24 inches deep......these are larger than typical framing. LVL's may come that deep but it is not worth getting them 32 feet long and 24 inches deep.....they would way a ton and it is not economical.

I would put in (2) 3" steel round columns, if you can, to help support the opening; these should sit on a thicker concrete footing and not just the concrete slab. I would still frame the opening with LVL's.....(2) 1 3/4"x 11 7/8"; these would sit on the foundation wall and the two columns. The truss joists can then attach to LVL's with joist hangers. The 3/4" OSB subfloor is adequate for spanning 16"o.c. Here is a diagram that I drew, based on what I imagined you were saying.


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