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Question DetailsAsked on 9/21/2011

Our basement often (but not always) has a musty smell. We've done a number of things, but we still have the problem. Any suggestions?

There is no mold as far as we can see. We had additional drainage around the perimeter installed and still get the smell.

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1 Answer


This one is wide open.

Mold often isn't seen and is still high on the list of suspects.

Start with moisture: Is your basement wet or moist? You can get a humidity device which will give you the moisture content in the air and or materials (it has probes you push against wall and building materials). Compare this to areas upstairs and outside to get an idea of how much more 'wet' the air is in your basement.

A dehumidifier is another option; if you set it to automatic, and it begins running, its humidistat is detecting moisture and turns it on. Try running a dehumidifier and see if this pin points the problem and or helps.

Are the A/C & Heat vents in the basement open? It is possible the basement's lack of conditioning / lack of air circulation is causing the smell. A fan to keep air moving, or an exhaust fan to pull air from the basement to the outside may assist.

Look for signs of actual moisture; discoloring on the walls, ceilings or floors. Standing water along the outside of the house, near basement windows, doors, etc. (which also indicates your perimiter drain is failing)

Is the basement finshed? Is it possible that an animal has created a nest in the walls, ceilings or unused portions? Is it possible an animal has died within the walls?

Why was 'additional drainage' added to your house? Did you have a water problem before? Who installed it and did they install it in repsonse to your problem with the musty smell before?

Was the drainage installed interior or exterior to the walls? When it rains, can you see where the drainage goes? (IE can you see where the perimiter drain comes out to open air or at the curb or storm sewer? Can you see that water is actually flowing out after it rains? You may have a clog or the slopes may be wrong in your old or even new system, and the sitting water may be causing the smell.

If you had a water problem before, it is likely you are dealing with mold or at least high humidity still in your construction materials. Removing any old gypsum board or panels and running dehumidifiers and heat in the basement to dry it out is a good idea. After you get all materials completely dry, reinstalling new gypsum board may help with the smell.

If you basement has floor drains, remove the covers and try cleaning out the traps below. If your system allows it, add bleach to kill any germs or bacteria that may be causing smells.

Get rid of any old books, clothes or materials that were saturated with water or have mildew.

Does your septic system have a clean out in the basement? Confirming that you don't have a septic system issue that is allowing gases to flow back into the house is something else to check for odd smells. A bad backflow preventor may be allowing 'goo' to sit in the pipes just inside your house, and the smell is escaping.

Check your heat pump if it is in the basement. If it has a filter in the system, make sure it has been replaced. People often change the filter in their return air but don't know they may have one in their actual unit, too.

You can get cheap mold tests at Home Depot. Follow the directions; either rub the strips on materials or place the canisters where directed. Send them in and get a report. You can also have professionals come do an assessment; but as with any estimate, if you tell them you fear you have mold, odds are good they will 'find' some mold. . .

Best guess: your perimeter drain work was because of moisture in the basement. This was not the problem or was installed incorrectly to solve the problem. The basement is still wet, so you are smelling mildew and mold. Install a dehumidifier and fans to circulate air to help dry out your basement.

Answered 9 years ago by Kenny Johnson

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