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2x12 joist span

5573 Views 3 Replies 4 Participants Last post by  Scuba_Dave
Is anybody out there an engineer?
I am working with a structural engineer who has made some seriously over-designed changes to the structure of my house. I was initially surprised, but made the changes because I want the seal on my drawings, so I can submit them to L&I for approvals.
I am at the end of the revisions, and she tells me that "upon a third review, the roof framing of 2x12 @ 16" oc will not work."

2 story structure. It is a flat roof, 1/2":12". 3/4" T&G deck, 2" polyiso - mechanically fastened, single ply epdm - fully adhered. Ceiling attached.
Joists are hung from 2x12 ledgers, HY-20 epoxy connections @ 16" oc into 8" CMU - solid grouted with #4 rebar @ 16" oc and horizontal ladders every other course.

Live 20psf, Dead 10 psf, ceiling attached, L/240

The span is 15'-1", with 1.5" bearing - joist hangers.

Why won't this work?
I have looked at all kinds of span tables and every source, including
ICC-IRC says it should work.

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· Banned
17,249 Posts
AH - flat roof - that will do it probably
I'm at 6/12 for a slope w/2x12's
Better slightly over-designed then under designed
To span 18' I went with I-joists
I even went one size bigger then spec to make the attic floor stiffer. You really don't want a lot of flex & drywall cracking

Where are you located?
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