Can we talk about the moisture content rule for hardwood over concrete?

I was reading a guide from the National Wood Flooring Association and it said the concrete slab needs to be under 75% relative humidity before you install. I found that out after a job in Tampa where we had to wait three extra days for a slab to dry. Has anyone else had to push back a schedule because of this specific number?

3 comments

3 Comments

taylor.jessica3mo ago

Yeah, that 75% rule is no joke. Learned the hard way on a project in Savannah, same kind of humid mess. You skip that test and you're begging for cupping and gaps later. It's a total schedule killer, but waiting is cheaper than a callback and a full tear-out. That guide isn't just making up numbers.

finley9393mo ago

Ugh, tell me about it. I rushed a job in Charleston and the boards looked like a roller coaster by October. That wait feels painful but it's nothing compared to a redo.

wren_smith4429d ago

Taylor was spot on about that Savannah humidity. That 75% rule feels like a pain but it's really just the difference between a job you can walk away from and one you'll be fixing a year later. I've seen guys in Tampa skip the moisture test and end up with boards that looked like they were trying to float off the slab. If you're ever on the fence about waiting, just remember that a week delay beats ripping out hardwood and starting over.