2 x 12 span
2 x 12 span
(OP)
Will a 2x12 douglas fir garage(75 psf)floor joist span 20 feet at 16 o.c. if I install 2 rows of blocking and use 5/4 t&g subfloor?
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RE: 2 x 12 span
Mike McCann
MMC Engineering
RE: 2 x 12 span
RE: 2 x 12 span
RE: 2 x 12 span
Space them at 12" o.c. and your bending stress is under 800 psi so would be okay for No 2's but still deflection may control.
RE: 2 x 12 span
RE: 2 x 12 span
Just out of curiosity where did you come up with 800psi for 12" spacing? I just did a quick check and got over 1400 psi (and that's for no load other than the 75psf).
M=75*20*20/8*12=45000lb-in.
S=1.5*11.25*11.25/6=31.64in^3
fb=M/S=45000/31.64=1422psi
Again, that's neglecting any other load besides the 75 psf, which he's likely considering as a LL.
OP-
This tells me that the 16" spacing won't work, the 12" spacing probably won't work (depending on the grade) for strength and/or deflection.
RE: 2 x 12 span
Mike McCann
MMC Engineering
RE: 2 x 12 span
RE: 2 x 12 span
At least we got the thing doing it two different ways (I do My/I...guess its no different than using section modulus it just rearanges variables..