How soon does mold grow after a water leak?
It can start inside two days. The EPA says wet materials dried within 24 to 48 hours usually will not grow mold. The CDC says that if a flooded house, including furniture, could not be dried in that window, you should assume mold is present, even behind cabinets and inside walls.
On this page
The clock starts when the material gets wet, not when you first notice a smell. Two federal pages put the same window on it.
What the EPA says
The EPA mold guide says it is important to dry water-damaged areas and items within 24 to 48 hours to prevent mold growth. In another line on the same page, it says that if wet or damp materials are dried 24 to 48 hours after a leak or spill, in most cases mold will not grow. The guide also asks you to keep indoor humidity below 60 percent, and ideally between 30 and 50 percent, once the room is dry.
That is a drying target, not a promise. Spores are already in house dust. They need moisture to grow.
What the CDC says after a flood
The CDC is stricter once outdoor water has been in the house. Its respiratory cleanup page says that if the home was flooded and you could not completely dry it out, including furniture and rugs, within 24 to 48 hours, you probably have mold. The same page says mold can hide under cabinets, carpet, cushions, or inside walls even when you cannot see or smell it.
What that means tonight
If the leak is still new and the water is clean supply water, moving air and pulling water now is the job. What to do when you find mold in the house is the order. If the house sat wet through a weekend, plan for hidden mold and for materials that cannot be saved.
In a Gulf city like Lake Charles, outdoor flood water is common enough that the CDC flood pages, not just the indoor-leak page, are the ones to read.
Sources
Who wrote this page
- Written by
- Mold Wise Home editorial staff. Who runs this site
- Licensed professional
- None. No licensed mold assessor or industrial hygienist has checked this page.
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