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. The log standard is silent on where that is measured, only specifying that max taper is 1/8' per foot. 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.