Asked on May 26, 2012

I am having odor issues in my house that I think are coming from the basement which has a mix of must and cat odor.

Cindy H
by Cindy H
The second floor doesn't seem to smell, which is why i think it's coming from the basement. It's worst in the morning. And when I turn on my heat or a/c, that odor comes through my vents! 1) I have a very good Santa Fe dehumidifier running, 2) I've had the ductwork checked and it's fine. 3) I've been told by multiple hvac guys that i just need to seal the air leaks along the galvanized ducts, which I've done with foil tape to the best of my ability. Could there be a problem with the hvac system beyond the air leaks? Do I need to take measures to seal the floor and walls to remove the odor in the basement?
  14 answers
  • KMS Woodworks KMS Woodworks on May 27, 2012
    it sounds like your HVAC system is "distributing" the odors... Until the odor containing materials are "cleaned" this will continue to be a problem. Is the basement non-sealed concrete?...My first step would be to get that covered...paint, sealer, epoxy...,,something.
  • Cindy,. air sealing will help keep the odors from getting upstairs, sealing the floors with foam etc also will go a long way to help stop this from getting up there as well. However, you must remove the offending odor originating points to really stop it from getting upstairs completely. Running the dehumidifier as well may help that musty odor, to some extent, but its expensive to do so. Do you have cats? What type of basement do you have? Cement floors? finished? Tell me more about the area where you believe the odors are coming from. Other pets? Age of home? I would purchase a black light, yes the ones if your old as me used when we were kids. Bring it downstairs in the evening when it is dark. Turn it on. All the glow you see is most likely kitty urine. That green glow is what is causing that foul odor. If its on the cement there are several products that will neutralize this smell for you. Natures Miracle is one of them. Found in your local pet store in a white bottle. You simply spray this on the green glowing areas which will neutralize those odors. You may need to do this several times, but that will eventually remove the kitty odors. The musty smell is mold. This is a water issue along with something that is allowing the mold to grow on that must be solved. Does your AC system have insulation inside of it? Many do have this where the AC coil sits, and quite often the inside of the furnace is covered with this insulation as well. This can soak up odors like there is no tomorrow. To help lower the musty odors you need to do this: Using ventilation in the basement, you need to clean all the walls and floors real well with bleach and water mix. 50-50 is the best. Then using fans and your dehumidifier dry well. Check the framing above. Using a bright flashlight look for fuzzy growth on the beams. If you see any of this, you also need to wash the beams as well. Spray the bleach solution taking care around wires and boxes. Then wipe clean with rag. This will take some time, but it will remove most of the mold that is causing the musty odors. The last thing you can do, is to use an Ozone machine. This works well if carpet is located on the floors or other items that cannot be removed easily to fix the smells and that may contain some of them trapped inside their fibers. These devices literately kill the cells in the materials that cause odors. We use these units all the time when doing mold and odor management cleanups. This can be done professionally and will go a long way to remove the odors. However one thing to remember, you must do it all, fixing one thing will only rid you of one thing. Sealing ducts cleaning them, running dehumidifiers are only Band-aids, that prevent odors from moving. You need to find the source and fix it in order to get final relive from the smells.
  • Cindy H Cindy H on May 28, 2012
    Thanks for your helpful and thorough replies! I have an unfinished basement, cement floors, no carpeting. The house was built around 1945. I just moved into the house less than 2 yrs. ago. Apparently the previous owners had a cat that was urinating on the cement. Had I known how difficult it would be to get rid of it, and that it would make its way upstairs I would not have bought the house. We used a blacklight and tried several products to clean the spots we could find -- Enzymes, Nature's Miracle, Odorxit, bleach... we still smell it. There is an open crawl space (the kind that runs along one full wall, there is half a wall and you hop up onto the crawl space.) That is where most of the damage was done (that too is cement.) After we cleaned it my husband painted the floor with Drylock paint thinking that would seal it for good. We still smell it. And unfortunately now that it's painted we can't access it anymore. Which is why i was considering sealing it professionally with that material that looks like a pool liner (sorry can't recall the name.) As for the musty odors-- we did have Basement Systems come in and check for mold and they could not find any. I don't know what happened down there before we moved in, but we have a french drain and sump pump so water hasn't really been an issue since we've been here. I have done experiments with spraying air freshener down there, and sure enough, the air fresher fragrance starts coming through the vents upstairs in my living room. When we painted down there, the paint smell came right upstairs through my vents. I wonder if I should get the ducts totally insulated with fiberglass? None of the contractors mentioned the insulation in my A/C unit or furnace system, so I will check that out. I can also try bleaching the place, but it's hard to clean the walls since they're cinder block. And it's a full basement, so pretty large area to clean! So very frustrating. Thanks again.
  • lots of good information. once the urine gets into the block walls and soil it is very difficult to remove. Many homes end up being gutted and or torn down as a result of this. The cement floor in the crawl space I assume was put down perhaps by the last owners in an effort to help prevent the smells. My guess is it gets worse as the humidity rises down there. Musty odors come from mold. This is a fact. Because no one has seen it does not mean its not there. Quite often then not only testing will find out the source. With air tests one can determine what kind of mold is growing and based on that information can arrive on where its growing as a result. As different types of mold grow on different types of materials. I have one question however, seeing the basement has a french drain system, Does this system contain a slot along the wall in which to allow any water that may leak from the wall to enter into it? If so that needs to be sealed. This can be accomplished by using a foam backer rod to fill the top level of the opening, then using a pourable or lots of caulking from tubes, this is covered over to prevent any moisture to enter from this area. Even though you say you are not having any issues with drainage. Does not mean that water is not seeping into the drain system, you just cannot see it. This damp soil that may also contain kitty smells can be the cause of your issues. As far as sealing the crawl space area with vinyl liner. This should not be necessary as there should be plastic under the cement if its done properly. If you have insulation on the ceiling of the crawl space or around the sill plates, it needs to go. Any older insulation can be trapping these odors that your smelling. Replacing this is not expensive at all and can help a lot. If sealing the french drain does not help, then I would suggest Ozone treatment. Reach out to me on the phone if you like and I can help you with this. Ozone will remove these odors with one or two treatments. However you must be out of the house while its going on. All plants and fish or any animals also. As the Ozone will kill them.
  • Cindy H Cindy H on May 29, 2012
    Yes the french drain is open on the top-- looks like it's soil covered with rocks and stones. It does get damp along the one wall that is facing the back yard (and our yard slopes a little bit toward the house.) I'll look into getting that sealed. could there be mold in there? Ozone-- yikes-- sounds serious. I read on the EPA's website that ozone, when administered in safe/appropriate levels, does not work to remove odors. And I'd be concerned with using higher levels than that- isn't it dangerous?
  • The EPA web site can be confusing. And your correct the ozone used from the units you purchase over the counter does nothing other then to mask minor odors and if not used correctly can get you sick real quick. The machines I use are Ozone Cannons. They produce very high levels of Ozone, So much so you cannot be in the room for more then one or two minutes once its turned on. The levels produced are such that it really does remove the smells. But you cannot be in the house, nor can pets, plants, or fish. Feel free to contact me for more info on this.
  • A good whole house dehumidifier may help. If you have block walls your basement can become musty. Block is porous.
  • Bonnie Bonnie on Feb 21, 2015
    This may sound silly, but I had a problem like that at my store (the building is over 100 years old) make sure the return air duct is clear. I had covered it up with furniture. ( I thought it would be fine because it wasn't completely covered, but it made the whole place smell like the basement. It was summer, and I was running a dehumidifier down stairs. Still that changed everything!
  • Norm Duffy Norm Duffy on Jan 20, 2017

    Try using Baking Soda,either by sprinkling on offending area or by just leaving an open box or two around the Basement/Cellar!

  • Sallie Wolff Sallie Wolff on Jan 22, 2017

    We used a vaporizer on a timer with a purification essential oil in it, it will kill the odors it will take a few weeks before you will notice that it will seep into the cement.

  • Dfm Dfm on Jan 22, 2017

    cat wee -oil based not water based. it needs an enzyme cleaner... and on unsealed surfaces it needs to be kept "wet" in order for it to soak in. natures miricle never really worked for me. to keep the cleaner wet cover it with plastic wrap, and let it sit. my go to is odor logic clean away. no i don't have stock in the company.....the stuff just works generally really well.

  • Arts Be Crafty Arts Be Crafty on Jan 22, 2017

    Does your dehumidifier also filter the air? They have ones that do both.

  • Eroque022810 Eroque022810 on Jan 22, 2017

    OK I get it because we have been in this house for 11 months. The carpet looked new in LR&DR like walking on a cloud. Little did we know that they had a cat and even had carpet replaced, prior to that I had arranged for them to remove carpet, and return the next day to install in between we had floor painted with kilz instant difference you would never know that they didn't train that cat. It has totally gone and the upstairs is all older carpet. So I would say repaint it with kilz and I mean the entire basement floor just make sure you pick up paint that will adhere to cement. I have a son highly allergic to cats and he showed no problems in house that's why I know that they replaced carpet but didn't address soiled area on floors first. It was truly gross, but when you purchase a home that had previous tenant you never know what you're getting into. I truly hope it helps you.

    • See 1 previous
    • Eroque022810 Eroque022810 on May 26, 2018

      I can't say how it blocks the odor but I can say that the smell of strong urine is completely gone. It was really strong in one corner but I started getting it seeping through and causing these spots on the carpet. I was having my lr and Dr painted and I asked the gentleman doing the work if he had any idea and right away he told me what the spots were, at the carpet place they confirmed what he suggested without us saying a word, use kilz. We have an unfinished crawl space so you can understand how that would also allow smells up but no smells since then.

  • Sallie Wolff Sallie Wolff on May 26, 2018

    I found a few vaporizers that I like the original one I purchased was from Young Living since then I have purchased from Puritans Pride for a way better price. The best oils for combating musty oders have been frankincense, Thieves, Melrose, & Purification are my go to's there are a few vendors that carry these. You can find essential oils in area stores more frequently now or online through vendors such as Puritans Pride, DõTerra, & Young Living, just make sure they are 100% pure organic & not aromatic or for aromatherapy oil these do not have the properties that are beneficial for killing the air born bacteria.