Are people doing non-PT plywood strips for rainscreen as in moist costal zones like BC and the Pacific Northwest?
finePNW
| Posted in General Questions on
I see a lot of discussion around PT furring for rainscreens, and folks tend to agree that in typical situations non-PT 1×4 (or similar) is robust. Is this true of Exposure 1 plywood strips of any thickness, and do folks use non-PT plywood strips in super rainy locations like the PNW or, better yet, BC where rainscreens have been required by law for decades already?
I’ve got a lot of 5/8” Exposure 1 plywood leftover after sheathing that I’d love to put to good use. Bonus points for reducing my crew’s poison exposures.
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Replies
finepnw,
For years both treated and regular exterior plywood strips were available in lumberyards here in BC, but now I only see the pt ones. Why that change occurred I don't know.
There are two schools of thought around how you detail siding and trim. Martin has always advocated not sealing the gaps (for instance between windows and trim) to allow drying. On rain-screens that comes with more wetting of the rain-screen furring. I prefer to entirely seal the outer layer of cladding and allow any necessary drying to occur into the cavity. Doing that I would have no hesitation in using regular plywood.
Interesting about the local lumber yards in BC and thanks for your thoughts on non-PR plywood! I’ll have to see if I can find any articles from Martin that indicate what he uses for furring.
finePNW,
I think Martin's approach was for walls without rain-screens, which makes sense. Without a cavity to dry into you don't want to trap moisture.
I don't see a problem with non-pt furring for a couple of reasons.
- It is located in an ideal place, where it is both protected by the cladding, and can dry easily.
- The furring is really just a spacer. Compared to the cladding, sheathing or framing, a bit of moisture damage to the furring doesn't affect much.