Thread: Vapor Barrier Needed?

Does a dirt floor crawlspace still need a vapor barrier if there are concrete joists and a concrete floor above the crawlspace area? Would moisture still evaporate through the concrete floor into the living space above? My thinking would be no, but I'm not sure.

Thanks

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Mr. Bacon,

Isn't concrete porous, wick water? Poured slabs have a continuous vapor barrier. Is the concrete water sealed underneath?

All concrete slabs below habitable areas/spaces should be provided with a vapor barrier. A concrete slab sitting on grade is nothing more than a very large tampon when it comes to wicking moisture out of the sub-soil. There is a jurisdiction in my area that has for years required a 2-ply asphaltic hot-mop VB below garage slabs due to the propensity of folks for eventually converting their garages to family rooms and/or sleeping rooms.

Originally Posted by Jerry McCarthy

All concrete slabs below habitable areas/spaces should be provided with a vapor barrier. A concrete slab sitting on grade is nothing more than a very large tampon when it comes to wicking moisture out of the sub-soil. There is a jurisdiction in my area that has for years required a 2-ply asphaltic hot-mop VB below garage slabs due to the propensity of folks for eventually converting their garages to family rooms and/or sleeping rooms.

Man and I thought everything was big in Texas

Jerry, very... er... descriptive explanation.
Jim

Jerry, My wife flipped last night when I hot mopped her box of Tampons. That was bad advice. Thanks alot

I apologize if I offended anybody with my description of what a slab foundation is capable of related to women’s hygiene products.
However, let's take another example. You ever notice when a newspaper is left on your lawn for any length of time and when you pick it up it's all wet where it was in contact with the grass?
Or, how about when you stand on the sandy beach and after a couple of minutes you move your foot and where your footprint was fills with liquid?
This is a natural phenomenon and slab foundation are notorious in drawing moisture from the soils.

Mr. McCarhy,

Just poking a little fun. You were direct and accurate both good qualities. I was trying to
get Mr. Bacon to think about his question. Could have added to my post wasn't half of
Chicago built on a drained swamp?