How long does it take for a floor to rot from water damage?

In water damage restoration, a wet floor brings two worries: mold and rot. They are not the same thing, and no official source puts a set number of days on rot.

Mold and rot are different

The EPA flood cleanup page says mold can grow on wood, drywall, carpet and furniture if they stay wet for more than 24 hours. Rot is wood decay, and it is a different problem.

NC State Extension says that having mold or mildew on joists or beams does not mean wood decay will occur. So a fuzzy spot on a joist is a reason to dry and clean, not proof the floor is failing.

How wet wood has to be to rot

NC State Extension says wood-decaying fungi do not grow below the fiber-saturation point of the wood, which it puts at 28 to 30 percent moisture. The University of California Cooperative Extension says decay fungi need liquid water in the wood, at more than about 28 percent moisture, and that some fungi can structurally break down wood.

Boards that do not bounce back

Some boards fail without rot. Mississippi State University Extension says wall sheathing made of oriented strand board, or OSB, is hard to dry and likely to swell after high water, and that replacing it is the only option. How to tell if water damage is permanent covers what else usually has to go.

How a crew checks that the floor is dry

NC State Extension says you need a wood moisture meter to tell if there is too much moisture in a crawl space, attic or wall framing. It also says not to seal up walls until the wood is at 19 percent moisture or lower.

Ask any crew to show you the meter readings before they close anything up. What to do when water is in the house has the first steps, and water damage in Cedar Rapids adds the local notes.