Crawl space vapor barrier.

I’m in California. Every home in my area is either a slab or a crawl. Going through the training I’m a bit lost on the crawl space vapor barrier. Should EVERY crawl space have the full plastic lined vapor barrier installed or only the ones that are encapsulated? If so, do you mark that as a defect or just ‘monitor’?

thanks all!

Just recommend installation of a vapor barrier on the dirt, by a qualified professional and move on to something else.

Of something is supposed to be there and is not, you would not “monitor” it. You would recommend installation by a qualified professional.

Here is some info on different types of crawlspaces: https://www.nachi.org/bbsystem/usrfiles/C/CI-Crawlspace_00-774.pdf

1 Like

Fantastic info Larry, Thank you. Do vapor barriers only apply to sealed crawls? or do vented ones need them to?

Thank you again for your time.
-Jason

info on crawl spaces

You might want to check with your AHJ for your area.

About California Ventilation Building Codes | Home Guides | SF Gate
The California building code states all underfloor areas must be aired by openings in the exterior foundation walls. The openings must have a total area of 1 square foot for every 150 square feet of underfloor.

http://www.cityofconcord.org/pdf/permits/building/trifold.pdf

Very rarely do I ever find a vapor barrier.

Seen less than a handful since I started in Nor Cal.

You might want to check with your local building codes.

Vapor barriers are not only not installed, they are NOT recommended in Southern California due to our very dry climate.

You’re much farther North, so it may be different.