My whole house is 3/4" t&g. Subfloors and roof decking is 6 inch wide
material, exterior wall sheathing is 10" wide.
Interior walls are also 3/4" thick - 3/8 plaster over 3/8" x 8" t&g
brown-paper covered gypsum-like material. Seriously, it's t&g gypsum
1956 colonial in western NY. Just a tad over-built. <g>
Since I wouldn't know how much I might need, I would wait 'til I
started the tear off before making the call on that sort of thing. I
would hate to show up with several sheets of plywood that I might not
need to use, or worse yet, guess at the thickness, but I am guessing
that things vary quite a bit regionally. I see mostly 3/4" as
sheathing, and sometimes thicker on really old (turn of the century)
He was on the roof though? Depending on how he inspected, he may have lifted
shingles and been able to tell from edges. Also, you dont say how much he
is replacing. If he' really replacing (as in all the wood layer), it doesnt
matter if he matches what used to be there.
Thats reasonable. Best to tell him too. Oh, I'd get a second estimate and
a 3rd <g>.
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.
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