On Feb 14, 6:14*pm, "
wrote:
On Feb 14, 5:10*pm, jamesgang wrote:

On Thursday, February 14, 2013 2:58:20 PM UTC-5, wrote:
I'm going to have to replace some sections of roof sheathing as part of a re-roof project. What is there now is 1/2" plywood. I guess it's been OK because it's lasted almost 30 years. Is 1/2" still OK as far as code goes, etc? The part that is a problem was due to not being vented correctly, which I'm going to fix. It's actually one entire section of roof where that whole section needs to be replaced. I'm going to get quotes and want to make sure everything is spec'd. What is typically used now for roof sheathing? Is OSB ok? is at as good or better than plywood? Oddly looking at Lowes and HD, it doesn't look like they have sheathing in 1/2". Closest is 15/32. I guess maybe lumber yards have true 1/2"?

Nobody has true 1/2" any more. *OSB is fine. *Stronger and cheaper. *OSB is used for almost all new construction. *Get the little clips to keep it spaced properly. *Why'd the original fail? *Should have lasted longer than 30 years. *Get wet?

It failed on one section that is a cathedral ceiling. The other
two sections have normal attics. *And the dumb asses did
not vent the cathedral part. *I guess I could have put a
ridge vent in, but I'm not sure it would have made much
difference. *I doubt they put baffles in and without them
the insulation is likely blocking the air flow all the way
from top to bottom in each bay. *Fortunately it's only
about 900 sq ft.

I did some googling on OSB vs CDX *plywood. *Seems
they are similar. *OSB is less expensive, more water
resistant. *But it appears if it does get wet enough, then
it won't return to the same thickness when it dries.
Plywood is easier to get saturated, but when it dries out,
it's more likely to return close to original size.

Looks like it will be 15/32. *I doubt that will make any
difference in aligning with any sheets that are still there.
It may not matter. *I think in the bad section, probably
going to have to pull it all to so as to put in the missing
baffles for air flow. * After tear off, there might be a sheet
or two that needs to be replaced on the rest of the roof,
so the 1/2 vs 15/32 would only be an issue there and I
doubt it matters.

Looking at the cost of various materials, one killer is the
ice barrier that I believe is now required by code for the
lower areas. *And I have long eaves, which requires more
of it because as I understand it, the ice barrier needs to
extend up 2 ft beyond where the roof meets the heated
walls. *That means I need two passes, each 3ft wide.
That stuff goes for like $79 for a 3ft by 36 ft roll of the
product made by Grace. * That's $790 just for that.
The freaking shingles for the whole 43 sq are only $1400.
Maybe there are other products that are less expensive?
Ice damming here hasn't been a problem in 18 years....

Just found out the Owens Corning has an ice barrier
product that is less than half the cost of the Grace one.
A lot more reasonable at $330.