How long can CDX be exposed for?
lightnb
| Posted in General Questions on
I haven’t been able to find a definite answer for this online. At what point does CDX “exposure 1” plywood warping, swelling, or delaminating go from “its our fault because we manufactured it wrong” to “its your fault for not covering it up fast enough”?
ie. It started raining before we could get the tar paper on, and it rained for five days straight and there’s issues. Defective material?
But what is the reasonable/allowed number of days for exposure to wet weather? 5 days of rain max? 10 days of rain? 30 days of rain? 6 months of rain?
This is climate zone 4a.
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Replies
I have a good test case for this: a doghouse roof. I put it on two years ago and then got busy and never put the shingles on (to match the main house). One side is a different lot number from the other, but both are CDX roof sheathing rated plywood. One side is just fine, no delamination at all, just discolored with that cape cod gray look.
The other side is a different story: some of the plys have wrinkled and buckled. A roofing contractor I frequently work with even said it shouldn’t get that bad. It only took a few months to start having problems on that side.
I’d say if you had five days of rain, and it got really messed up, then you probably had a bad lot. The exposure rating is supposed to let the material be exposed for a reasonable period of construction, which I’d think should be at least a few weeks to a few months. Unless you had some kind of major deluge for five days with a long period of mugginess after so the material could never dry out, I think you have a case with the manufacturer.
Whether or not they’ll do anything about it is another story entirely.
Bill
Lightnb,
By necessity we frame in the rain here in the PNW. I've occasionally had a few small spots of delimitation on subfloors, but never on wall sheathing. As Bill said, If you are experiencing widespread failure there is something wrong with the plywood. It's rated for exterior exposure during construction.
In my case should I be contacting Boise Cascade or the yard I purchased the plywood from?
I’d try the yard first, but you’ll probably end up talking the manufacturer in the end.
Bill
I built an outhouse in 1974 and sheathed the walls with CDX plywood. Never covered it with asphalt felt or siding. After 47 years exposed to Vermont weather, it looks fine. No delamination.
Of course, these days, they don't make CDX like they used to.