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What is the best material to use on top of plywood for water proofing?
Babak K
July 27, 2020Updated: Sept. 25, 2020
If cost was not a concern, what would you recommend is the best material (durable, high quality) to use for Water Resistive Barrier on top of Plywood? I have heard mixed reviews on Zip Systems as something production builders use since it's easy to install but don't know which type of material is good? E.g. Asphalt felt, Plastic houewrap, Liquid-applied WRB, Rigid Foam, Delta Dry etc.
For help choosing a weather barrier for the exterior of a home see here –
Choosing a house wrap, which is best?
In our 2015 LEED Platinum Demo house we installed a peel and stick weather barrier / exterior air barrier, see our how to install an air barrier properly DIY video. ZIP systems are a good ‘all-in-one house sheathing / weather barrier product, but you wouldn’t put that over existing plywood. Are you still in the design phase or have you started building already?
Thanks Mike! I'm still in the design phase. Hasn't started constructionyet. I read the article you referenced, very insightful. Also watched the viedeo. So would you say Plywood + Peel and sticks (Vent SA from Cosella-Dörken) is the best way to go for optimal outcome? Any tips on which materials to use? Plywood thickness, tape or fluid-applied gun, which brand?
Hi Babak, Plywood is a bit of a in improvement over OSB as sheathing if you're looking for the ideal wall assembly to allow walls to dry. The Vent SA is a great product we were really happy with, though that doesn't mean there aren't others. If it's hard to source near you, you may have luck finding a comparable product for a lower price. Online you should be able to find spec sheets to compare products. As for the thickness of plywood I'd leave that more to the designer to determine. As you saw in the video, we applied the primer to the sheathing with a roller in preparation of the peel and stick membrane.