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Discussion Starter · #1 ·
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.


Remodeling Contractor
3,590 Posts
You are close to the limits here and an engineer will allow for snow loads for the worse known conditions in your area. Better to be a bit over than under built.

17,248 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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