Why does my garage stink?

August 1, 2023 5:20 PM

My attached garage has an odor. It’s not mildew, it’s not pet odors. It just smells very musty. I’m guessing it’s due to damp, but could it be something else?

It’s a 1965 ranch. We moved in a year ago. I don’t think the previous owners stored their car in there, and we don’t either. The climate is damp—Berkshires— and the stairs leading from the basement (under the house) to the garage (on a concrete pad) are a little wet after all the rains, but no other sign of dampness or water intrusion. I’m not totally sure the odor is due to dampness, though. Would cleaning the floor with something acidic (muratic acid) and painting the cinder block walls help? Do I need to run a dehumidifier (and if so, is there a dehumidifier that can somehow be rigged to drain out the door or window? The house is not occupied all the time).

Any suggestions? It’s so bad that when we open the door between the garage and the kitchen, everyone in the kitchen groans.

posted by Ollie to Home & Garden (5 answers total)

Definitely try some Damprid or something similar.
posted by hydra77 at 5:54 PM on August 1, 2023 [3 favorites]

Since it's a garage, can you leave the door open for several days to air the space out? Alternately, you could start with a dehumidifier, if for no other reason than to see how much moisture it pulls out of the air, just to gauge the scale of the damp. Once the area is drier, you might be able to better pinpoint the source of the musty smell. And yes, heavy cleaning is a good next step, and necessary before you add another coat of paint. If it smells musty, it is certainly mold or mildew. Just because you can't see visible mildew doesn't mean it's not there. Is there a crawl space over the garage? Cinderblock is very porous. Drywall and insulation can also be culprits, as can wood framing.
posted by amusebuche at 9:46 PM on August 1, 2023 [1 favorite]

Does the garage have a drain? The one in my mother's house had one, about 15x15 centimeters covered by a metal grill and not only did a musty smell emanate from there but it also turned out to be an entry point for rats.
posted by 15L06 at 3:58 AM on August 2, 2023 [1 favorite]

Some dehumidifiers come with pumps and a hose attachment, so you can have it pump at a higher elevation than the dehumidifier sits at. I've had one that does this. Rental might be an option if you're looking to just test it as a solution.

I've never run a dehumidifier in a garage; if it's got a lot of airflow etc. from the outside, I don't know if it would be very effective as you'd essentially be trying to dehumidify the world. If it's pretty tightly sealed, though, it might be worth a shot.
posted by Shepherd at 4:10 AM on August 2, 2023

Are there places rodent poop could hide, such as behind shelves? Mouse poop doesn't smell like large mammal poop, but it's an unpleasant, musky odor. Not sure if you have hantavirus in your area but it can also be a health hazard. Looks like little black seeds, about the same length as a sunflower seed but more cylindrical.
posted by wnissen at 9:09 AM on August 2, 2023