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pttcc 08-22-2010 02:48 PM

distance from plywood shear wall to foundation
 
I have two contractors who gave me different opinion what to do.

The outside of my shear wall will be flush to the outside of concrete foundation. So plywood will sit on top of concrete foundation. I don't know if I need to leave a gap between them.

A contractor told me I need to leave at least 1/2 inch to avoid moisture. Another told me plywood needs to be on top of foundation directly to have a strong shear wall.

I know this is only about half an inch. But still I still want to do it right. btw, I live at San Jose, California.

Any help will be appreciated. Thanks!

Joe Carola 08-22-2010 03:13 PM

Quote:

Originally Posted by pttcc (Post 489540)
I have two contractors who gave me different opinion what to do.

The outside of my shear wall will be flush to the outside of concrete foundation. So plywood will sit on top of concrete foundation. I don't know if I need to leave a gap between them.

A contractor told me I need to leave at least 1/2 inch to avoid moisture. Another told me plywood needs to be on top of foundation directly to have a strong shear wall.

I know this is only about half an inch. But still I still want to do it right.

Any help will be appreciated. Thanks!

Plywood cannot touch the foundation. A gap is necessary. 1/2" might be code where your from, I don't know. Bottopm line is that there has to be a gap between plywood and foundation.

Gary in WA 08-22-2010 07:00 PM

"A contractor told me I need to leave at least 1/2 inch to avoid moisture. Another told me plywood needs to be on top of foundation directly to have a strong shear wall."---------- To get shear and uplift resistance with a APA structural plywood sheathing or panel siding, it needs to be installed even with the bottom of the p.t. plate. There is single row and double row nailing, with different ratings for the on-center applications of the fasteners. The double row requires the row of fasteners to be 1/2" up from the bottom edge, 1/2" between rows, and 1/2" from the top edge of the plate.



To avoid moisture and create a thermal break, add a sill sealer under the bottom plate: http://docs.google.com/viewer?a=v&q=...Sf-fmaa9ayOUVg

APA: http://www.apawood.org/pdfs/download...naged/H335.pdf

Check with your local B.D. if still in doubt.

Be safe, Gary

pttcc 08-23-2010 11:18 PM

Thanks, Joe and GBR.

I went to BD today. The inspector told me: don't leave gap. stay flush with pt mud plate/sill plate. :)


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