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Old 03-31-2009, 08:12 AM   #1
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2x12 joist span

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.



phillybr is offline   Reply With Quote
Old 03-31-2009, 08:20 AM   #2
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Why didn't you ask your engineer? It may involve snow load.


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Old 03-31-2009, 09:27 AM   #3
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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.
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Old 03-31-2009, 09:38 AM   #4
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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?
Scuba_Dave is offline   Reply With Quote

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