Wood flooring over wet slab

Old 02-22-15, 01:11 AM
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Wood flooring over wet slab

I am under contract with a house that has a slab foundation that is wet. I haven't been able to do too much exploratory work, but as far as I can tell so far the current flooring consists of a sheet of 6 mil directly on the slab, 2x4 sleepers with foam board in between and plywood on top. It is deteriorating in spots (you can fall through if you jump) I'm not sure why it's wet yet (condensation, high water table) but the gutters are dumping at the side of the house and the property is graded all wrong with no drainage. I plan on fixing that immediately and taking it from there.

I no expert yet, but I am thinking another part of the problem is the 6 mil plastic directly on the slab. Isn't this going to draw moisture and condensation up? I've seen a few websites recommending doing this to draw moisture out as a test. Wouldn't I be better off leaving air down there so things can breath? I was thinking of doing it again except without the 6 mil plastic on the slab or maybe skipping the plastic. Perhaps a product like DriCore would serve me well.

Any thoughts on all of this? I would love to be able to install hardwood to add more of a "cabin" feel to this tiny house of mine.
Old 02-22-15, 04:13 AM
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Welcome to the forums! My best advice is to RUN !! Unless you can find out why the slab is wet, rid it of everything damaged by moisture, and start over with a guaranteed dry slab, it will be a money pit from the day you sign the contract.

Moisture is one problem. The inevitable mold problem will be even larger.
Old 02-22-15, 06:25 AM
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I agree with Chandler on this one.
In addition to what he mentioned if it's an older home several other things that was often done years ago was to run steel or copper tubing for the supply's through the slabs, at some point it's all going to leak and have to be reran through the walls or over head.
I've even seen the metal duct for the heat ran through the slabs.
Guess what, it all rust out and grows mold that gets blown through out the house.
If it's that wet what do you think this did to the bottom plates and bottom sections of the studs in the wall?
Old 02-22-15, 06:25 AM
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I've seen a few websites recommending doing this to draw moisture out as a test.
The poly doesn't draw the moisture out, it is already there. The poly merely traps it prior to evaporation. Many say they have a dry slab only to have moisture present when they do this test. I'm with Larry, proceed with extreme caution. You are lucky that you know in advance, the sellers are hoping to dump their problems on you.

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