Fastening into T & G sheathing diaphragms

[Structintern3]

Hey guys, I'm working on a project with a floor diaphragm with a 4" slab over 1 1/8" T&G Sheathing and a roof diaphragm of just the sheathing. I'm designing kickers for storefront headers into the diaphragm (relatively small nonstructural interior header loads) and am not sure if I can just fasten into the sheathing and count on it? What is you guys' experience fastening your partitions and such into a T&G diaphragm, is there somewhere I can find values for this?

Thank you in advance!

 

[phamENG]

A 4" slab over wood structural panel floor sheathing? You mean a concrete slab? Why?

Setting aside the odd (to me) construction choice...it depends which of those things is your diaphragm. Is the concrete slab the diaphragm, or is the sheathing the diaphragm? You just have to follow the load path. If the concrete is the diaphragm and you fasten to the sheathing...you need another connection to go from sheathing to the concrete.

 

[milkshakelake]

@phamENG Unless I'm mistaken, I think OP means to support the kickers, not generally use the concrete as a diaphragm. If I'm wrong about that, I'll modify my answer, because there's a way to do it.

@Structintern3 Depends if the kickers are going into the underside or top side.

Top side connection: Since 4" is a lot, if the forces are compression+shear only, you can probably fasten directly into the slab and not worry about fastening to the T&G sheathing. If it's tension/compression+shear, you're better off fastening into the T&G diaphragm. As for capacity, I don't know about T&G specifically but NDS has tables for allowable load capacity in psf for thick plywood, and I'd assume it's similar. If you have a linear load, you can probably just extrapolate to psf. If it's concentrated loads, I'd use a plate to spread the load and connect directly to joists. The plate would be invisible because it's covered by the 4" concrete. The plate would also have a tangential benefit of being a kind of shear key to laterally tie the concrete and T&G together in that area.

Bottom of T&G connection: Why not run a horizontal plate/beam and connect directly to joists? Then you don't have to worry about the diaphragm vertical flexure capacity.