Vapor barrier over interior CMU piers in a crawlspace-what is the point?
JeffS1
| Posted in General Questions on
In online photos and in actual crawlspaces that have been conditioned I mostly see the vapor barrier run to the top (or with termite inspection gap) of interior CMU piers, three/four feet above the ground surface. Why is this done? Code only requires it be run up the foundation walls 6″ in my CZ3A. Is wicking the reason? I never see this discussed.
Thanks for any insights. Jeff
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Replies
Because you want to control moisture and keep moisture out of the crawl. Moisture migrates through concrete, both cast in place and CMU. So you bring the vapor barrier up as far as you can, so moisture migrating up the piers has less surface area to dissipate out into the crawl. As you noted, they can't take it to the top because they have to leave the termite gap...and even in areas without termites, it is easier to terminate the vapor barrier sheet good on the vertical surface.