![]() The log standard is silent on where that is measured, only specifying that max taper is 1/8" per foot. I also wasn't sure on that I didn't know if it should be 40 and that was snow load and roof weight or if it was just snow weight and I had to add an extra 10 or 20 for the weight of the roof itself.įiguring tributary area 2' spacing x 10' span x 55 psf = ~1100 lbs total load up with a 6.8" dia in a sawn round timber beam (SRTB). Some other calculators said "horizontal span" this one just said "span". This might also be of interest to from: Don P on January 01, 2021, 07:59:49 PM Holler if any of that is unclear or just plain wrong. but I wouldn't, I'd just be conservative and stay a little bigger. If this has no brittle finishes like plaster you can use the bending strength diameters and accept more sag. That will yield a roof with a max deflection of L/360. So your minimum small end dia inside the bark, ignore the max 3/10 dia flat, is ~6-1/4", midspan, where bending moment is maximum is ~6-13/16" min. For round beams Hahney says that is midspan dia and I feel that is a safe assumption for SRTB's bearing the taper rules in mind. I'm using a span of 115" and coming up with a 6.8" dia in a sawn round timber beam (SRTB). That would be a combined live load of 40psf + a dead load of 15psf for a total of 55psf.įiguring tributary area 2' spacing x 10' span x 55 psf = ~1100 lbs total load Being steep, so longer along the slope, I'm going to use 15psf. ![]() Technically that is calculated on the slope but in common practice most folks use the same run of the roof. The dead load is usually assumed to be 10-15 psf. ![]() Next, you used the snow load of 40psf but neglected the weight of the materials themselves. At a 12/12 pitch and a 14' rafter length, the horizontal run is 10'. I see a couple of problems, see if this checks out.įirst is the snow load is taken on the horizontal span of the roof.
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