A musty smell in the house is usually not the problem itself. It is a sign that something is still wet, often somewhere you cannot see, like under the flooring, inside a wall or above a ceiling.
This post covers what causes a musty smell, what we found in a downstairs unit in Camarillo where the smell showed up after a leak from the unit above, and why fans and pulling up some carpet are often not enough.
What causes a musty smell in a house
- Water that did not dry. Carpet pad, drywall, insulation and wood hold water long after the surface feels dry.
- Mold or mildew growing where you cannot see it. The EPA’s guide to mold and moisture notes that you may suspect hidden mold if a building smells moldy but you cannot see the source.
- A leak that is still going. A slow drip from plumbing, a drain line or the unit above keeps feeding the same spot. If you cannot find it, our post on leak detection walks through how the source gets tracked down.
- Closed spaces. Closets, cabinets and the space above a ceiling do not get airflow, so they dry slowly.
What we found in a downstairs unit in Camarillo
The unit upstairs had a plumbing leak, and water came down into the bedroom and the bathroom next to it in the unit below. The tenant set up fans and pulled up some of the carpet, but afterward she started noticing a bad smell in her unit.
March 17: the first visit
The photos from the first visit show a box fan running on the floor where the carpet had been pulled back, stains on the floor along the baseboard, and an opening in the ceiling with a plastic bag hung underneath it.
March 26 and March 30: readings and opening the walls
On March 26, the crew took readings on the walls, floors and around the tub, and the bottom of the walls was opened. Behind the drywall, the wall cavities had broken drywall and debris at the bottom. A dehumidifier was running, and its display showed air coming in at 52 percent relative humidity and going out at 18 percent.
By March 30, plastic containment was up and readings were being taken at the base of the open walls, where the framing meets the floor.
April 20 and April 28: putting it back
By April 20, new drywall was up and textured. By April 28, new flooring was down.
Why fans and pulling up carpet are not always enough
This is the part where most people do exactly what this tenant did, and it makes sense. Fans move air across surfaces. They help the top of the carpet and the face of the wall dry, but they do not do much for water that soaked into the pad, the bottom of the drywall, the framing or the space above a ceiling. That trapped water is what keeps the smell coming back.
The EPA says water damaged areas should be dried within 24 to 48 hours to prevent mold growth, and that absorbent materials like carpet and ceiling tiles may have to be thrown away if they become moldy. Our post on mold after water damage explains why that window matters.
How to find where a musty smell is coming from
- Follow your nose. The smell is usually strongest near the source, like one closet, one corner or one wall.
- Check under sinks, behind the toilet and around the tub or shower.
- Look at the ceiling, especially if there is a bathroom or kitchen above you.
- Look at baseboards for stains, swelling or paint pulling away.
- Lift a corner of the carpet and look at the pad and the floor underneath.
- Think back to any leak, overflow or spill, even one that seemed handled.
If the smell started after water came through the ceiling, our post on water damage on the ceiling covers what that usually means.
When to call someone
- The smell started after a leak, even one that looked dried out
- It comes back after cleaning and airing out
- You see staining, swelling or soft spots on walls, floors or ceilings
- The leak came from another unit and you cannot see where the water went
- You see mold growth
Our post on mold behind drywall covers what happens when a wet wall stays closed.
FAQ
Will a musty smell go away on its own?
Not if something is still wet. Air fresheners and open windows can cover it for a while, but all you end up with is a wet wall that smells a little like vanilla. The smell comes back as long as the source is there.
Is a musty smell always mold?
Not always, but it usually means moisture. The EPA notes that a moldy smell with no visible source can be a sign of hidden mold, which is why the source should be found.
Who is responsible when the leak came from the unit above?
It depends on the lease, the HOA or building rules and the insurance policies involved. Report it to your landlord or property manager right away and take dated photos. Our post on mold in a condo covers who is usually responsible after a leak from another unit.
Noticing a musty smell after a leak?
Total Restoration handles water damage restoration in Camarillo and across Ventura County, Santa Barbara County and Santa Clarita. We find where the water went, open what needs to be opened and dry it out properly. Contact us to get it checked.