I have moved into a rental house and the garage has a musty odor of which I cannot tolerate to breathe so I cannot even park my car in the garage.


  • I put in a HEPA filter and let it run for 2 weeks, a big air purifier that covers the size of my garage
  • and then left a dehumidifier on for a week in the garage also
  • also left a $20 DampRid container in for two weeks

all of which did not solve the problem, so, while leaving the garage door all the way open for the next 2 weeks, I did this:

  • bleached the floor with 3 cups bleach per 1 gallon of water, spread with a mop, and let it sit overnight, then washed it off,
  • then did the same again the next week, then washed it off, all while the garage door is still fully open
  • then using a degreaser and letting it sit while continuing to moisten it per instructions,
  • then washing it off,
  • and then powerwashing the whole floor in the same way that I cleaned my outdoor driveway, which took hours,
  • all while the garage door sat all the way open for the last 2 weeks
  • and I have also painted 1 wall, but the other 2 walls and ceiling I am waiting for more paint to arrive and I will do that too. (I have now painted all the walls.)

and still, although much improved and while the garage door is all the way open there's barely any smell at all, as soon as I close the garage door for a few minutes, the musty odor begins to get strong. After mere moments I feel a bit lightheaded from the strong odor - making me think this must be some mildew or mold, but I don't see it.

  • the previous tenants moved out and left the house vacant for four months.
  • the house is only 9 years old
  • the garage faces north
  • there is concrete blocks on the wall for about 1.5 feet from the floor to the base of the drywall
  • there is a 5 inch hole in one of the walls (which I have now repaired)
  • the bottoms of the drywall have a gap between the wall and the concrete block underneath. (I have now used foam backer rod and plan to use caulk to finish sealing the gap)
  • I cannot identify any mold or mildew anywhere. Just unfinished drywall and very clean (at this point) concrete slab floor. (I have now painted all the walls. But not the ceiling as I ran out of paint.)
  • my landlord is ok with doing the things.

The reason I want to solve the problem is because I would like to live here for up to 2 years (maybe longer?), but I need the garage, and otherwise the house is perfect for me and it took a long time to find a place decent and I'm tired of moving, so I do not want to move, which by the way would cost more than sealing the garage floor.

As a last resort I considered sealing the concrete. I can have it done for $750, but that's too much for a rental house. I plan to rent a diamond grinder, and then use industrial epoxy to seal up the floor. It will cost about $250 to do it myself with tool rental and epoxy.

My reasoning is that if I fill the hole and gaps, and paint the walls and ceiling, also paint the concrete blocks at the base of the walls (the paint is rated for concrete blocks as well as drywall), and seal the floor with epoxy, then I don't see how any smell could get through if it's all sealed over.

  • Will doing all this solve the problem?
  • Do I really need to do all this to solve the problem (I've already bought the paint, but have't bought the floor sealant stuff yet)?
  • Do you think that the 5" hole and the gaps at the bottom of the drywall may be where the smell is coming from, or do you think it's the concrete floor? Or maybe the concrete block portion of the wall at the bottom?
  • Is there a way to test where the odor is coming from?
  • Any other advice?

Need to solve this problem, hope you can help.

  • 3
    You are throwing various products and money at things in the hope that you will find and eliminate this odor. Perhaps you might call in a specialist who can positively identify the source and propose a solution.
    – jwh20
    Aug 31, 2020 at 9:52
  • You've alluded to a simple solution that would cost very little--an exhaust fan. Ask whether your landowner will allow the installation of a wall or roof fan that would continuously circulate air through the space.
    – isherwood
    Aug 31, 2020 at 14:19
  • Is this musty odor from a rodent infestation? Aug 31, 2020 at 19:24
  • Do you see rat or mouse excrete or other evidence of a rodent infestation? Aug 31, 2020 at 19:42
  • No. There are no rodents.
    – diy
    Aug 31, 2020 at 22:43

1 Answer 1


Is there a lawn mower or any other equipment you keep in the garage. If so, take it out for a couple of days and see if the smell let’s up. If that’s not it, there’s probably mold behind the sheet rock; especially if you have an outdoor sprinkler that wets that part of the garage. Drill a finger sized hole into the wall. Put on white glove or use a white hanky to stick into the hole and touch the back of the sheet rock.

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