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Strong Odor After Crawlspace Encapsulation

Donna54 | Posted in General Questions on

I also have this problem and know water and lots of it at times is flowing under the encapsulation.  A drainage system with sump pump to pump out any water was installed under the encapsulation however, while it works it doesn’t take care of all the water.  I see evidence of that.  The company that installed the encapsulation came back out and sprayed foam around the A/C unit where the water is coming in but it still isn’t stopping the water.  I am working with my HVAC company to have the A/C unit moved further away from the house as it is in a low spot.  I have a landscape company that will install a drainage system on the outside of the house to direct the water away from that low area.  Bottom line is I read that black mold can cause a urine smell which of course alarmed me.   If indeed there is mold under the encapsulation, what has to be done to remediate it? I do have a dehumidifier.

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  1. Jon_R | | #1

    Keep your crawlspace at a low humidity (with the dehumidifier). Also install a small exhaust fan so odors will be directed outside.

    1. Donna54 | | #3

      Thanks for the info.

  2. user-2310254 | | #2


    In general, you want to have the ground sloping away from the foundation. If that's not possible, you can sometimes have the land graded to create sways that help to channel water away from the foundation. Gutters with downspout extension also are a good idea.

    When your liner was installed, was the crawlspace wall insulated and were the vents closed? If you did these things and the crawl space still has a lot of humidity, you might need to install a dehumidifier.

    Mold under the encapsulation shouldn't be an issue as long as the liner is completely sealed. But high humidity could cause mold to grow elsewhere in the crawl space.

    1. Donna54 | | #5

      Hi Steve,
      Yes the walls were insulated (over the vents too)and a dehumidifier was installed. I see its running when I go in the crawl space and doesn't feel damp until after a heavy rain. While there is tape at seems, they didn't tape 100% along all seems and since we are in a red clay area, I see where water finds it's way at those areas and see puddles of water standing at times. I am hoping the landscaper will correct the sloping issue and can finally put an end to water going under the house. Once we can stop the water I think I am hearing the odor will go away.

      1. user-2310254 | | #7

        I would tape all the seams. Otherwise, you are attempting to bail out a boat that has a hole in the bottom.

        1. 1869farmhouse | | #11

          I have to second this! An encapsulation is an all or nothing proposition. One should work to achieve 100% seal knowing that maybe 98% is the best possible real world outcome.

  3. Expert Member
    Peter Engle | | #4

    There is another obvious possibility for urine odors - rodents. Even a small amount of rodent feces/urine on top of a plastic floor covering can generate a lot of odor if the crawlspace is damp. Have you had any rodent activity?

    1. Donna54 | | #6

      I am not seeing any evidence of rodent droppings underneath or inside the house. But maybe setting a mouse trap would be a good idea. Thank you.

  4. brian_wiley | | #8

    In researching a liner system for my own encapsulation project, I ran across several forum posts (on other forums) as well as some posts on crawlspaceninja that associate liners that have a built-in mesh reinforcement with a “cat pee” smell. It was totally anecdotal, but also enough of them to make me think twice about getting reinforced liner. It may be worth a look though.

    Also, having done mine in two sections, I would strongly second Steve’s comment about the need for taping all seams. I got interrupted on my project and left a small section unfinished for a couple of weeks. The musty crawlspace smell persisted until the very last area was completely taped on mine, even though the entirety of the floors and walls were covered.

    1. Expert Member
      BILL WICHERS | | #10

      That sounds strange to me. Reinforced liners have a mesh sandwiched between two layers of the same material as the liner (typically polyethylene). That means the mesh isn't exposed to the air, so it should have no impact on the smell of the liner. My guess is people claiming the mesh liner smells probably did a rip out and replace of an old liner, and the smell isn't from the new liner, it's from something that was either exposed or disturbed (or both) during the remove/replace process.


      1. brian_wiley | | #12

        I agree. I can’t think of any logical reason why that would occur when the supposed offending part is itself encapsulated, but it also came up in so many places that it seemed hard to ignore on some level. There has to be a more logical reason (exposure during the remediation process like you said) though.

  5. Expert Member
    KOHTA UENO | | #9

    Bottom line is I read that black mold can cause a urine smell which of course alarmed me.

    As another possible source of this odor--fiberglass insulation often has binders that emit a 'cat pee' or similar smell, especially when wet or heated. Is there fiberglass insulation installed in the crawl space?

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