huangyhg

rafter cuts on structural ridge
i'm working on a project with a structural ridge of 3-1 3/4x18" lvls. is it bad practice to cut a flat spot on the rafters to sit on top of the structural ridge or does that take away from the rafter weight load?
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generally, rafters are framed to the side of the ridge beam, but not a problem to cut flat spot on bottom if you are framing such. check shear at the cut point to make sure you have adequate section.
as an alternative, you may want to consider something like a simpson vpa clip, which would save the tedious cutting of flat notches in the rafters
it depends on what your rafters are. if you are using engineered lumber for rafters such as lvl or wooden i-beams you don't want to notch them. if you are using sawn lumber it is ok.
the problem with notching the lvl lumber is that you create a stress concentration that can split the engineered lumber easier than it would split sawn lumber.
notching a rafter to sit on top of the ridge beam is the same as notching the bottom (birds mouth) to sit on the top plate. to be sure, check your remaining section as ron said.
pylko, i respectfully disagree. notching the top of a rafter to bear on the ridge beam creates a wedge between the bearing surface and a short line of grain, which is vulnerable to splitting with loss of bearing. it is generally a poor practice. notching the bottom creates no such problem, so long al the level cut is fully supported by the plate. also, notching the top creates the need for blocking.
generally you can notch a dimensional rafter (i.e. 2 x 12) for a load bearing ridge no more than one-fourth the depth of the rafter used. so for a 2 x 12 that would mean a notch no deeper than 2-13/16". note: you cannot notch a wood-i joist.

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