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Re: Wood Diaphragm Edge

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If shear loads are low enough, Simpson H10 clip to attach truss or rafter at
eave to top plate of wall, has shear transfer capability.  If located at
every roof framing/wall intersection and roof framing is 24" oc, then
lateral load is V/2 (lb/ft).  Top plates of wall serve as diaphragm chords.

For higher shear loads, wood structural panel roof sheathing should be
nailed to blocking between trusses or rafters, then blocking should be
toenailed to top plate, or connected with Simpson A35 or similar flat plate
for shear transfer to top plates. I would not use blocking that has holes
for ventilation, for diaphragm blocking. Nail lateral load would be affected
by lack of nail penetration into framing at holes; also horizontal shear
capacity of blocking is affected by holes.  Better to "double up" on nailing
at alternate blocking members (without ventilation holes), to transfer shear
at these locations. My house roof has "bird hole" blocking between every
other (alternate) trusses.

John Rose/APA, Tacoma, WA

Jim Kestner wrote:

> We typically provide solid blocking in every 3rd space between roof
> trusses to bring the roof diaphragm load down to the shear wall. The
> Architect says he has to have venting in every truss space and does not
> understand why we need this blocking. We suggested that he have a
> continuously vented soffit and add venting between the trusses where the
> blocking is not required.
>
> I thought about using Simpson H1 clip to help take the load down to the
> wall, but then you still don't have sufficient edge nailing on the
> diaphragm.
>
> Any suggestions?
>
> Jim Kestner, P.E.
> Green Bay, Wi.
>