Temporary water leak and mold

Q: Last night my humidifier leaked a few cups of water onto the wood floor of my daughter’s bedroom. We discovered the leak maybe 20 minutes after it had started and we cleaned it up, but this morning I found a little puddle of water in my basement directly below where the humidifier had spilled. Is it possible the water went through the floor and the ceiling into the basement? What’s the best way to make sure the floor dries and doesn’t mold? 

A: Clearly that is what happened and it actually is a good thing. The water ran right through rather than pooling and soaking into the board edges. I wouldn’t worry about mold. It requires a constant moist, warm environment to thrive.

Follow-up: That’s such a relief, thank you so much for your quick response! I live in Seattle so mold is always a problem. I’m glad my floor won’t be damaged. Thanks so much again, I feel much better!

A: I’m guessing you are in an older home that perhaps has individual planks of pine for example as a sub floor? I’m guessing that because the water seems for the most part to have leaked right past the sub floor into the basement. If you had plywood subfloor for example (which is a good surface to work with) the water would have soaked that and it would have had to evaporate through the floor to finally dry. So, given the small amount of water, that it didn’t pool and you got right on it…I doubt you will even have any cupping of the floor. Even if you do, I’ve seen it flatten after. If you had an ongoing leak over a long period of time you might have a mold issue then. Not in this case.

Related Q: Our laundry room pipes burst in the cold and flooded down into our kitchen. The wood was sealed with two coats of stain and three coats of varathane, but the water sat for several hours and has gone through the cracks. The boards are now curved up at the edges in a concave shape.

We have been running 2 dehumidifiers, but it’s cold and water isn’t coming out. We have a gas fireplace and it’s running strong. I am worried about making sure the subfloor doesn’t get moldy. Thoughts? We think we can sand down and refinish the floor. Thank you!

A: For mold to be a problem, alive and growing it needs a constant environment of moist warm air. If the floor is installed on plywood that likely means it didn’t seep into the basement so it is sitting on the plywood surface and underside of your hardwood floor. Without actually removing the damaged section of flooring it could take some weeks to thoroughly dry everything out and you wouldn’t want to sand the floor until that happens. You will need a moisture meter for wood to keep checking until you get readings 7-9% or at least close to that.

Similar Q: Our window AC unit leaked water inside and onto our carpeting/OSB subfloor. We dried carpeting, ripped out padding and are drying subfloor with fans/dehumidifier. Subfloor doesn’t look bad at all. However, there is water damage on ceiling below from leak. Do we need to replace subfloor? Clearly it leaked through. What is likelihood of mold developing in between subfloor and ceiling?

A: You aren’t talking about a huge amount of water trapped which will take months to dry out. Mold needs a certain constant environment to grow and thrive. Constant warm, damp or wet environment. I wouldn’t worry about it. Just make sure everything is really dry before doing any painting or putting your carpet back.

Similar Q: Our refrigerator leaked for quite a while before we noticed the floor in front bowing. We have real Brazilian cherry floors. The floor man said to let it dry thoroughly and then he will lightly sand and then refinish. We live in South Carolina where it is hot and humid, I’m afraid that the sub-floor will be moldy.

A: Under the circumstances It may be wise to remove the damaged area and let everything dry out. I assume this is factory finished flooring. Jatoba does change colour rapidly with light exposure so expect to see a difference between the old and new wood which should change rather quickly.

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