Blocking question

[msquared48]

Anyone know a code stipulation stating that blocking is still required for a plywood roof diaphragm using T&G plywood?

This a repair going from 1/2" OSB to a 3/4" diaphragm, where access from the bottom is problematical as it is a food processing complex..

Mike McCann, PE, SE (WA)

 

[Ron]

My understanding is that it's either/or....blocking or T&G.

 

[KootK]

From the perspective of in plane shear capacity, your T&G would still have to be considered an unblocked diaphragm. For most thicknesses, your tongue is only 3/8" long which doesn't facilitate the installation of any shear transfer nailing. An exception to that is monstrously thick 1-1/8" T&G which has a 7/8" tongue that, supposedly, you can get some shear nailing into. Still sounds a bit dodgy to me.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

maybe you spec some epoxy on the tongue?

 

[Triangled]

kinda like KootK,
i understand two issues going on:
1. unsupported edge of sheathing, which may be addressed with T&G, plywood edge clips or plywood edge blocks
2. blocked diaphragm shear values, for which i haven't considered as yet any alternative to nailed/stapled wood
code requirement

roofing membrane may have an unsupported sheathing edge requirement ...