Mold After Water Damage: How Fast It Grows and What to Do
Mold can start growing on wet materials within 24 to 48 hours, so the most important thing is to dry everything fast. Small spots on hard surfaces you can usually clean yourself with soap and water. Wet drywall, insulation, carpet pad and mattresses that stayed wet usually have to go. For larger areas, roughly more than 10 square feet, or if anyone in the home has asthma or a weak immune system, call a professional.
After a leak or flood, the water is the obvious problem. Mold is the slower one. It's not an emergency in the first hour, but it becomes one if things stay wet for days. The good news is that you can prevent most of it by moving quickly.
Why the first two days matter
Mold spores are already everywhere, indoors and out. They just need moisture and something to feed on, like drywall paper, wood, carpet or cardboard. The U.S. Environmental Protection Agency advises drying water-damaged areas and items within 24 to 48 hours to prevent mold growth. After that, growth is likely, especially in warm, humid weather.
- Hour 0 to 24Stop the water. Remove standing water. Get fans and a dehumidifier running. Pull wet rugs, cushions and boxes out of the room.
- Hour 24 to 48Keep drying. Open cabinets and closets. Move wet belongings somewhere dry. Call a water damage company if walls, floors or ceilings are soaked.
- Day 3 and beyondAnything still wet is at real risk. Watch for a musty smell, spots on walls, or staining on the backs of furniture.
Signs you have mold
- A musty, earthy smell, especially in closets, basements or under sinks.
- Spots or fuzz that are black, green, white or gray, often in clusters.
- Stains or bubbling paint on walls or ceilings where water was.
- Allergy-like symptoms that get better when you leave the house.
You usually don't need a mold test. If you can see it or smell it, you have a moisture problem to fix, whatever type of mold it is. Testing can make sense in some situations, like a dispute or a hidden problem, but it's not the first step.
What you can clean yourself
For small areas on hard, non-porous surfaces (tile, sealed countertops, metal, glass, hard plastic):
- Wear gloves, goggles and an N95 mask.
- Scrub with detergent and water, then dry completely.
- Fix the water source first, or it will come back.
- Never mix bleach with ammonia or other cleaners. It makes toxic gas.
The EPA's general rule of thumb is that areas smaller than about 10 square feet (about a 3-by-3-foot patch) can often be handled by a homeowner. Bigger than that, follow professional guidance or hire a mold remediation company.
What usually has to go
Porous materials that stayed wet more than a day or two often can't be fully cleaned, because mold grows into them, not just on them:
- Drywall below the water line
- Wet insulation
- Carpet pad
- Mattresses and box springs
- Upholstered furniture soaked through
- Cardboard boxes and paper
- Ceiling tiles
- Stuffed toys and pillows
Some of these can be saved if they're dried quickly or professionally cleaned. Rugs are a good example: see rugs after a flood. And photos and papers can often be frozen and rescued later: see saving wet photos and papers.
When to call a professional
- The moldy area is larger than about 10 square feet.
- Mold is inside walls, ductwork or the heating and air system.
- The water was from a sewer backup or flood water.
- Anyone in the house has asthma, allergies, a lung condition, or a weakened immune system.
- You keep cleaning it and it keeps coming back.
Look for a company that uses containment (plastic sheeting and air filtration) so spores don't spread to clean rooms, and that gives you a written scope of work.
Does insurance cover mold?
It depends on why the mold happened. Many homeowners policies may cover mold that results from a sudden, covered water loss, like a burst pipe, often with a lower dollar limit just for mold. They usually don't cover mold from a slow leak that went on for months, from poor maintenance, or from flooding (unless you have flood insurance, which has its own rules).
That's another reason to act fast and document everything: photos of the water, the date you found it, and what you did to dry things out. It shows you took reasonable steps to prevent more damage.
The bottom line
Dry everything within two days if you can. Clean small spots on hard surfaces yourself, let porous things that stayed wet go, and bring in a pro for large areas, hidden mold or anyone with health concerns. Photos and dates help your claim.
General information only, not medical, legal or insurance advice. People with health concerns should talk to a doctor. Follow EPA and local health department guidance for mold cleanup.