Replies

1. Expert Member
   BILL WICHERS | Jan 28, 2019 10:31pm | #1

   There is a product called “natures miracle” that is sold in pet stores. It’s an enzymatic cleaner that breaks down urine. Try cleaning the liner with that, then wash with water, then use a bleach solution to finish it off. Be careful you don’t lift any taped seams.

   If it still smells after that, then you probably have to replace the liner.

   Bill

2. 
   tommay | Jan 28, 2019 11:45pm | #2

   Anything living under there? Any leaking drain pipes?

3. 
   KeithH | Jan 29, 2019 02:28am | #3

   Ideas regarding the smell:
   - What's on the crawlspace walls for insulation? Anything? Formaldehyde smells like cat pee, lots of insulation uses it as a binder.
   - Is there new plywood/osb/particle board anywhere? Like maybe subfloor above the crawlspace? Another source of formaldehyde.
   - How about the glue used for the liner? It's rarely a one piece liner. Perhaps you could install tape over the glued seams. I have found Dow Weathermate tape to be moderately priced, able to stick to some plastic radon membranes while tolerating the liner's wrinkly nature, and without odor. If it's a glue problem, the smell would get better with tape. If it's something inside the crawl space, I bet taping the (probably leakily glued liner seams) will make the smell worse.

   As for ripping the liner out, that sounds expensive ($1/sf?) and unproductive and will make a lot of plastic waste and will probably result in new plastic and new glue (how is that better?).

   Different idea:
   What about getting a small ERV/HRV and air exchanging the crawl space? Perhaps a Lunos (see writeups elsewhere on GBA) or a Panasonic spot? If you are handy with ducting, you could self-install one of these for not a lot more than ripping out that membrane, depending a bit on the size of the crawlspace. Just an idea. Even cheaper (but a lot less energy efficient) would be to install a bathroom exhaust fan and control it with a thermostat that has a programmable refresh mode on a program or timer? (Panasonic makes some ECM bathroom fans that, while wasting ventilation air energy, would at least operate efficiently).

4. 
   gozags | Jan 31, 2019 10:12pm | #4

   The radon system is taking moisture out of the soil and reducing the fuel for the microbes that are feeding on the soil trapped beneath the plastic liner.

   I have probably read the same things you have and I tend to believe that’s the situation you have.

   Perhaps taking a soils PH reading. Then selectively and systematically puncturing the membrane, adding something to neuralize the PH then affixing high quality tape to close up all the punctures.

   I thought I may have the same issue, though from sealing off an old basement (that previously could evaporate moisture into the interior). Our issue, we believe, was actually cat/pet urine in a select area. TSP, hot water cleanses and then liberal application of the Amazon basics enzyme cleaner seems to have worked.

5. 
   Chris_Duncan | Jan 31, 2019 10:32pm | #5

   You need to diagnose the source before you proceed. Are there liquid puddle stains on the plastic? Is there a cat sized access hole anywhere? Maybe a rodent size hole? Look for droppings. They can cause a similar smell. If it really is urine and not something mimicking it, then some baking soda water (4 heaping teaspoons to a quart) in a hand bottle sprayer, or even one of those pump garden sprayers will kill the smell and not hurt anything. Bleach is going to ruin some tapes so I would be careful with that, maybe do a test area if going that route.

1. Expert Member
   MALCOLM TAYLOR | Jan 31, 2019 11:15pm | #6

   Now I think about it - I have no idea where my cat pees. I hope he isn't sliding over to Thomas's place and peeing in his crawlspace.

2. 
   KeithH | Feb 01, 2019 03:06am | #7

   Scene: The kitchen of a suburban household, western Idaho.
   Husband, David, at the counter with a beer. Enter stage left, wife, Sarah.

   Sarah: Honey, I went in the crawl space to change the furnace filter and it smells like cat pee down there.
   David: Drinks beer.
   Sarah: Could you go see if there are mice living down there?
   David: Drinks beer.
   Sarah: Please
   David: All right (enters crawl space)
   David, shouting up to Sarah: Yeah, it smells like pee.
   Sarah: will you look around for the hole they are getting in?
   David: Can you get me a flashlight?
   Sarah leaves kitchen
   David: Smells more like cat pee than mouse pee
   Sarah returns
   Sarah:: Here's the flashlight (hands David flashlight)
   David: I'm going to look around
   Sarah: Ok, I'm going to go take a shower (horror movies always have the women showering alone)
   David: You are leaving me! Fine, I'll go crawl off to be eaten by a giant mouse alone!
   Sarah leaves kitchen
   David crawls and crawls (it's a big crawl space, also spiders).
   David: My gosh, what's the giant hole in the ground? That hole is huge! It smells so bad (coughs)
   David: What's all this white dried crystalline dust?
   Ground collapses!
   David falls into the sinkhole full of mating garter snakes.
   David: Snakes! Anything but snakes!
   Sarah: Did you say something honey? Honey??

6. 
   MSVA | May 19, 2021 02:57pm | #8

   Hi,
   How old is the house (when was it built)? Was it ever treated for termites with a chlorinated pesticide? We have similar problem and wondered if that could be the reaction going on.
   Thanks!