On Apr 6, 11:52 am, Wayne Whitney wrote:
On 2008-04-06, DerbyDad03 wrote:

I have 3/4" tongue & groove under the shingles, not plywood. He didn't
look in the attic.

If you are in a high wind or seismic area, you may wish to consider
going over all the T&G 1x with 1/2" plywood to improve the shear
resistance of the roof. Of course, the wall sheathing would be more
important to strengthen, but it is presumably not accessible.

At $45/sheet? You're pretty free with the guy's money. The house has
been standing for 50 years, so there's little benefit to be gained
from an extra layer of sheathing. I also don't like adding weight to
a roof unnecessarily.

R