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Re: Plywood rigid diaphragms

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Michael said:

"This is a good idea, but if you still have some wood shrinkage at the sill
plate or the floor joist, now the bolts are no longer tight in the post holes
and you may have the 1/16" oversized hole effect again.  In evaluating
existing buildings, you may find that the actual post hole is greater than
1/16" and that the combined shrinkage of the rim joists and wall sill plate
and double top plate may be 1/2" or more.  This shrinkage can play havic with
the shear wall deflection"

How about cutting the sill plate so that the post with the holdown bears
directly on the slab. On the second floor, cut the sill plate and dbl top
plate, add a solid blocking between 2nd floor wall post and 1st floor wall
post with the grain parallel to the post grain. This will reduce wall
deflection due to wood shrinkage.

OR..... How about asking Simpson or any other hardware company to come up with
a holdown anchor/nut/bolt assembly that selfs tighten as wood shrinks. Maybe a
friction type nut that works one direction only and as the wood shrinks, the
nut moves down on the anchor bolt but is restrained from moving upward.
Technically, if all present Holddowns causes shear wall deflection to exceed
the code allowable, we can say that none of these holddown are in compliance
with the code and we can force the manufacturers to come up with an approved

Ernie Natividad