Mold is a fungus that grows on damp materials like carpet, carpet pad, drywall, and wood. After a leak or flood, it can start growing within a day or two if wet areas aren’t dried out. Soft materials that stay wet are hard to clean and usually have to be thrown away. Floors with no hidden layers, like coated or polished concrete, give mold far fewer places to hide.
Why Mold Matters After a Basement Flood
Mold grows where there’s moisture, including anywhere there’s been a flood. That puts a wet basement floor at the top of the list. The clock starts as soon as the water arrives, because wet areas and items need to be dried within 24 to 48 hours to prevent mold growth.
Flooring is where that clock is hardest to beat. Mold can grow on the underside of carpets and pads, where you can’t see it. A floor with layers underneath it is like a wet sponge sealed in a plastic bag. The top may look fine while the bottom stays damp.
Where Mold Hides in Basement Flooring
- Carpet and pad. These soak up water and dry slowly. Carpet and upholstery that were soaked and can’t be dried right away should be removed or replaced.
- Under click-together floors. A floating floor sits on a layer of underlayment, and water trapped between them is out of sight and hard to dry.
- Drywall and wood trim. These wick water up from the floor.
Hard, sealed surfaces are the easy part. Mold can be scrubbed off hard surfaces with detergent and water, then dried completely. Porous materials such as carpet may have to be thrown away once they’re moldy.
What to Do About Mold and Your Floor
- Stop the water. Fix the leak, drainage issue, or sump pump problem first.
- Dry fast. Aim to fully dry out your home within 24 to 48 hours after a flood.
- Pull out what can’t be dried. Soaked carpet and pad usually go.
- Clean hard surfaces and let them dry completely.
- Keep the air dry. Hold indoor humidity below 60%, ideally between 30% and 50%. A dehumidifier helps in a basement.
- Pick a floor you can clean. Our guide to basement flooring after a flood compares options that don’t trap water.
For a small patch, under about 10 square feet, you can usually handle it yourself. For anything larger, bring in a professional. If anyone in your home has asthma or other breathing problems, keep them away from the cleanup and talk to a doctor about any health concerns.
Mold FAQ
What kills mold?
On hard surfaces, mold can be removed with soap and water, household cleaners, or a bleach solution of no more than 1 cup of bleach per gallon of water. Bleach isn’t recommended as a routine part of cleanup, though. Removing the mold and drying the area matters more than killing it.
Is it okay to just paint over mold?
No. Covering mold doesn’t remove it, and the moisture feeding it is still there. Clean it off, dry the surface, and fix the water source first. The same goes for putting new flooring over a damp, moldy slab.
Do I need to test for mold?
Usually not. If you can see mold growing, sampling is unnecessary in most cases. Spend the money on cleanup and fixing the moisture problem.
Is mold harmful to humans?
Mold can cause problems for some people, especially those with allergies, asthma, or weak immune systems. Keep sensitive people out of moldy areas during cleanup, and ask a doctor about any health questions.