Cupped Floors... in Winter

Craig DeWitt Headshot
efflorescence in crawl space

I got called to this house to look at a cupped floor (in the winter no less), but the complaint was really about work done to correct crawl space moisture. The flooring contractor was actually concerned about the exposed soil in the crawl space and recommended that the crawl space be fixed before the floors went in. Yay for him. The homeowners then made a few inquiries and got a few quotes. The quotes ranged from a little over $3,000 for plastic ground cover and a dehumidifier to $14,000 for total encapsulation with taped ground cover, wall insulation, a sump system and dehumidifier. They chose something in between that included covering the soil with a patented flow-able concrete/vermiculite material specially designed to make crawl spaces dry.

The crawl space was treated, the floors went in, and things were great for a month or so. Then the floors started to cup. The crawl space repair people came back, fixed some soft spots, coated the surface with something, and swapped out the dehumidifier for a bigger one. The crawl space stayed wet.

The first thing I noticed was all the efflorescence on the concrete stuff in the crawl space. The photo shows my pen lying on the concrete mix next to some efflorescence.

efflorescence in crawl space

Now, efflorescence forms when water moves through concrete and evaporates from the surface. So water, and a lot of it, was moving through this fancy crawl space soil sealing material. I checked the patent and sales literature, which said that sometimes a plastic liner is installed under the concrete mix to help control moisture. This house had none.

So their $12,000 system failed for lack of a plastic ground cover. In reality, the concrete mix's only function was to hold the plastic down.  It couldn't, wouldn't, and didn't stop the water. The cheapest solution is to have a plastic ground cover installed over this fancy concrete mix. The homeowners want the stuff out of their crawl space, and their money back. And as usual, I probably won't hear the rest of the story.

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