What thickness of vapor barrier paint do you need to apply instead of a poly vapor barrier?


The thickness of vapor retarding latex paint - Is measurement wet or dry?

Kim Boas Published: July 24, 2020, 10:36 a.m.Last updated: Aug. 6, 2020, 4:14 p.m.

I am applying a vapor retardent latex primer to my concrete basement floor and would like to know if one coat is thick enough.  The thickness cited in an ecohome article was 0.00031. The technical data for the paint has a wet thickness that matches the article but a much smaller dry thickness.  

Responses (3)

Kim Boas
Kim Boas July 24, 2020, 4:53 p.m. Reply

I'll be putting latex floor paint over the vapor barrier primer.  Since the house I recently moved into has an open stairwell to the basement, there is a musty / mildew smell. I've foamed and put 6 mil poly in the open crawlspace connected to the basement and painted the bare concrete walls with drylok. The floor was painted with latex, so I couldn't use the drylok floor paint. The latex vapor barrier paint seemed like a reasonable option.  

Mike Reynolds
Mike Reynolds July 25, 2020, 11:56 a.m. Reply

I wouldn’t be comfortable weighing in too much for or against, I’m just not sure how well it will work since it really isn’t the intended purpose. Not to say it won’t work, but if it’s a really damp floor I wonder how well the paint will hold or if it will end up chipping or something. It isn’t a bad idea as a starting place since it’s a pretty cheap way to try to solve the problem, but you may get better insight from checking with a manufacturer. You may also want to check with a paint or floor finishing store to see if they have ideas too. Worst case scenario is that it doesn’t work, and from there maybe you may have to do an actual poly vapor barrier and a floating floor of some kind. How old is the house? I’m just wondering if there may be a vapor barrier under the concrete if its reasonably new, if its pretty old there wouldn’t be, so it would be a lot more humid and that may affect how well it works.

I assume you've already gone the dehumidifier route? That's the first step to  instantly lowering basement humidity, just mentioning it in case you don't have one.