What Does Mold Smell Like? Finding the Musty Smell
Why mold smells musty, what the EPA says a moldy odor means, where hidden mold usually is, and how to remove the smell for good instead of covering it.
Find the source of a musty smellQuick answer
On a painted, washable wall, scrub small patches of mold with detergent and water and dry the wall completely; on tile, a diluted bleach solution is optional. Mold that comes back on drywall is usually growing in the paper facing or behind it, which cleaning cannot reach. The EPA says not to paint over mold and puts the do-it-yourself limit at about 10 square feet.
Key takeaways
- Painted walls: detergent and water, gentle scrubbing, then dry completely.
- Mold that returns on drywall is usually growing inside it or behind it.
- Do not paint over mold: the EPA says paint applied over moldy surfaces is likely to peel.
- Over about 10 square feet, the EPA says it is a job for a professional.
- Fix the moisture: dry wet walls within 24 to 48 hours and keep humidity low.
How to remove mold from walls: the short answer
Clean small patches on washable surfaces; treat mold that returns on drywall as a problem inside the wall.
Mold on a wall is two different problems depending on the material. On tile or a glossy painted surface, it is growth on the surface that you can scrub off. On drywall, the gypsum core is covered in paper, which is porous: mold can grow into it and behind it, and cleaning only reaches the front.
This guide takes each wall type in turn. For bathroom and kitchen detail work on washable surfaces, professional deep cleaning services handle the scrubbing; growth inside walls is remediation.
First: surface mold or mold inside the wall?
Surface mold wipes off and stays off; mold inside the wall comes back, stains through or smells musty.
Answer these in order
- Does the mold wipe off and stay off for weeks?It was on the surface.Keep the area dry
- Does a stain come back in the same place after cleaning?It is likely growing in the drywall paper or behind it.See when to call a pro
- Is the wall soft, bubbled or stained from a leak?Water is getting into the wall.See when to call a pro
- Is there a musty smell with little visible growth?Mold may be hidden behind the wall.Read about finding a musty smell
The EPA lists "the back side of dry wall, wallpaper, or paneling" among the places mold hides, and says "you may suspect hidden mold if a building smells moldy, but you cannot see the source." More on that is in what does mold smell like.
Wall by wall: what to do
Hard, sealed surfaces clean well; porous ones often need replacing.
| Wall type | Can you clean it? | Method |
|---|---|---|
| Ceramic or porcelain tile | Yes | Detergent and water; a bleach solution is optional; rinse and dry |
| Glossy or semi-gloss paint | Small surface patches | Detergent and water with a soft sponge; dry completely |
| Flat or matte paint on drywall | Limited | Gentle wiping only; stains that return mean growth in the drywall |
| Wood paneling, sealed | Surface patches | Damp wipe with detergent, dry quickly; no soaking |
| Unfinished wood | Limited | Mold can grow into wood; deep growth needs a professional |
| Wallpaper | Rarely | Mold often grows behind it; the EPA lists the back of wallpaper as a hiding place |
Step by step for a small patch on a painted wall
Protect yourself, wipe gently with detergent and water, dry the wall and watch for the stain returning.
- 01Measure the area. Keep to less than about 10 square feet, a patch roughly 3 feet by 3 feet.
- 02Protect yourself and the room. Wear rubber gloves and goggles, consider an N-95 respirator, and move furniture away from the wall.
- 03Wipe with detergent and water. Use a soft sponge on paint; hard scrubbing can remove paint and scuff drywall paper.
- 04Wipe with clean water and dry. Dry the wall completely with a towel and a fan.
- 05Bag the sponges and cloths. Wash or throw away what you used.
- 06Check again in a week. If the stain returns, the growth is in the drywall, not on the paint.
The options for stubborn spots on tile are in does bleach kill mold and does vinegar kill mold.
Rather have a pro handle it?
See deep cleaning and get a quoteGet matched with a local deep cleaning pro who serves your ZIP code. Free to request, no obligation.
Why you should not paint over mold
The EPA says not to paint or caulk moldy surfaces: the paint peels and the growth stays.
Do not paint or caulk moldy surfaces.
The same guide explains why: "Paint applied over moldy surfaces is likely to peel." Paint marketed for damp rooms can be used on clean, dry walls once the moisture problem is solved, but it is not a way to cover existing growth.
How to keep mold off walls
Stop condensation and leaks, move air along exterior walls and keep humidity low.
- Dry water-damaged walls within 24 to 48 hours, as the EPA advises.
- Keep indoor humidity no higher than 50%, per the CDC, with a dehumidifier in damp rooms.
- Leave a few inches between furniture and exterior walls so air can move.
- Run bathroom and kitchen fans, and fix leaks at the source.
Keep it from coming back
Start a recurring cleaning planRegular visits catch moisture, grime and buildup early. Set up a weekly, biweekly or monthly plan with a local pro.
When to call a professional
Call a remediation specialist for areas over about 10 square feet, stains that return on drywall, or walls damaged by leaks.
The EPA puts roughly 10 square feet as the limit for cleaning mold yourself, and notes that porous materials may have to be thrown away once moldy. Returning stains, soft or bubbled drywall and musty walls after a leak are remediation and repair. A cleaning pro handles washable surfaces such as tile and glossy paint in kitchens and bathrooms.
When the job is bigger than a spray bottle
Request deep cleaningA local deep cleaning pro brings the right products, protection and time for the whole area, and tells you when a specialist is needed.
FAQ
How do you remove mold from painted walls?
On a small patch, wipe gently with detergent and water using a soft sponge, wipe with clean water and dry the wall completely. If the stain returns within a week or two, the growth is in the drywall, not on the paint.
Can you paint over mold?
No. The EPA says not to paint or caulk moldy surfaces and warns that paint applied over moldy surfaces is likely to peel. Remove the mold, fix the moisture and let the wall dry first.
Does mold on drywall mean the wall has to be replaced?
Not always, but often. Drywall is porous, and the EPA notes that porous materials may have to be thrown away once they are moldy. Surface spots that wipe off and stay off are fine; stains that return mean growth inside the drywall.
What is the best thing to clean mold off walls?
On tile and washable paint, the EPA method is detergent and water, then drying completely. A bleach solution is optional on hard surfaces like tile, never mixed with other cleaners.
Why does mold keep growing on my walls?
Because moisture keeps reaching them: condensation on exterior walls, leaks, or high indoor humidity. Keep humidity no higher than 50%, move furniture away from exterior walls and fix leaks.
When should I call a professional for mold on walls?
When the area is larger than about 10 square feet, when stains return on drywall, when the wall is soft or bubbled, or when there is a musty smell with no visible source.
The bottom line
Mold on tile and washable paint is a cleaning job: detergent and water, then drying. Mold that returns on drywall is growing inside the wall, which cleaning and paint cannot fix. Keep walls dry, never paint over mold, and bring in a professional for large or returning growth.
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About the author
Consultor SEO WendersonSEO consultant and editor of the CleanLocalPros guides
Consultor SEO Wenderson writes the CleanLocalPros house cleaning guides from search data, official sources and the questions homeowners send us, and the editorial team reviews every guide before it is published. We do not accept payment for recommendations. More about the author · Our editorial standards.
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