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Suggestions/advice on vapor barrier product to use?

justinlstine | Posted in General Questions on

In the basement of my house (built in 1900) in NE Ohio…Half of the basement floor is finished, the other half is dirt floor covered by a few inches of crushed stone gravel. I had a mold issue, so looking to put a vapor barrier over the gravel floor. Also am getting slightly elevated radon level about about 4.9 to 5.1. I’m hoping maybe to solve both issue with one fix. Here’s my dilema…I’m looking for a vapor barrier material that would withstand occassionally walking across it. The furnace is located on the gravel side of the basement, as well as we use that area for storage (holiday decorations, etc). There wouldn’t be heavy traffic, but would need to walk over to change furnace filters, swap out holiday decorations, etc. Can anyone recommend a product that would act as a vapor/moisture barrier that could withstand some foot traffic? Thanks for the help!

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Replies

  1. justinlstine | | #1

    Also, the barrier would be installed on top of the gravel, so looking for something that wouldn't be easily punctured by the crushed stone gravel underneath. Thanks

  2. GBA Editor
    Martin Holladay | | #2

    Justin,
    1. Remove the stones.

    2. Install 20-mil pool liner or Tu-Tuf on bare dirt.

    3. Install a walkway above the vapor barrier (plywood or OSB).

    More information here: Building an Unvented Crawl Space.

  3. charlie_sullivan | | #3

    Depending on how aggressive you are about dehumidifying after you stop the moisture from flowing in, you might get mold on the wood if it's laying on the ground even above the plastic. It will be cold from the ground and thus more likely to get condensation that wood at a higher temperature would. So you might include some EPS foam insulation either above or below the 20 mil plastic to thermally isolate the wood from the concrete. And/or you might use cement board (tile backer board) as it is more moisture tolerant and mold resistant. Pressure treated plywood might be another option, but I'm not actually sure how mold resistant it is, or how the prices compare.

    If you include EPS foam below the plastic, that could also save you some work, because you wouldn't need to haul gravel out, and as a bonus, if you do a large area, it will help reduce your heat loss to the ground in the winter, and, by keeping the space a little warmer in the summer, make it a little easier to dehumidify. You could then do the walls too if you want.

    You will get a huge benefit by laying the plastic down, both on moisture and radon, but you might want to seal the edges with caulk or tape to essentially eliminate the influx of both.

  4. justinlstine | | #4

    Thank you both for the responses. I've attached photo of the area. Ideally, it would be nice to not remove the gravel as there is quite a lot, and being in the basement having to go upstairs. Would putting eps down first, and then the vapor barrier (have heard good things about tu tuf), be an ok way to go? I would be afraid the moisture would eventually lead to mold on the foam?

  5. justinlstine | | #5

    Here's a second photo

  6. GBA Editor
    Martin Holladay | | #6

    Justin,
    If you put the vapor barrier on top of the stones, it may last a long time. Or not -- depending on how much traffic it sees.

    Certainly the best approach would be to install a thin concrete slab (a "rat slab") over the new vapor barrier.

    Installing rigid foam is optional -- but it's certainly true that the rigid foam would protect the vapor barrier from the sharp stones.

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