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gcz
Joined: 27 Aug 2004
Posts: 2
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 Posted: Fri Aug 27, 2004 1:12 am Post subject: how to do calcs for wood truss, i-beam config |
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can someone tell me what i'll need to do the calcs for a wood truss, i-beam configuration, doug fir 2*4 and plywood web for the deflection/load on a 20 ft span?
i want to use up my form lumber to make a flat roof that is all deck.
(gable roof can cost 25% of framing labor/material and is really just an expensive umbrella to keep rain off the ceiling - instead, i want it all to be usable space)
the house is in the mountains, never any snow, just views - have to take advantage of the natural beauty and not waste usable space on the lot! |
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JWmHarmon
Joined: 15 Apr 2004
Posts: 115
Location: Ohio
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| Posted: Mon Aug 30, 2004 3:24 am Post subject: Plywood box beam alternative |
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You may want to consider a plywood box beam instead of an I-joist if you are making your own built-on-site rafters.
The link below refers to a garage box beam to support roof loads. it includes tables that you may be able to adapt for your application. It might be wise to seek the advice of a structural engineer for such a project.
The link below shows construction details for the box beam.
A box beam uses dimension lumber such as 2X4's sandwiched at the top and bottom between two sheets of plywood. The plywood is nailed or glued and nailed to the outside edge of the dimension lumber. You can include insulation inside the box as you manufacture it.
http://www.apawood.org/pdfs/managed/Z416.pdf |
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gcz
Joined: 27 Aug 2004
Posts: 2
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| Posted: Tue Sep 07, 2004 1:22 pm Post subject: |
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thank you jwmharmon - that was a perfect doc for box joists
if only i could find a similar document fot i-joists!
i checked all over the apa site...
looks like i'll have to have a chat with the neighborhood structural engineer and put out some cash |
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jimhenry
Joined: 17 Sep 2004
Posts: 2
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| Posted: Fri Sep 17, 2004 12:02 pm Post subject: box beams |
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| residential building code has perscriptive path design for box beams. also, look for a SIP (structurally insulated panel) mfg in your area - they will likely have them |
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