Checking subfloor moisture level: always necessary?


Old 07-11-11, 11:47 PM
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Join Date: Aug 2008
Location: USA
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Checking subfloor moisture level: always necessary?

I read a while ago on a flooring FAQ something to the effect of the following: "A good test to find out whether your flooring contractor is competent is to ask him whether he checks the subfloor moisture level. If he says no, find a new contractor."

A few days ago, I brought in a contractor for inspection (while still leaving open the possibility of installing the floor myself) and asked him the question. His response was that checking the moisture level would only be "necessary" if he were installing a floor in the basement, not the first floor or the second floor (where the installation would be done). The way he worded his answer made it unclear whether he WOULD check the moisture level in other situations, but his answer seemed at least somewhat plausible: I'm in Pennsylvania, which is not a place that has extreme levels of humidity, and he knew that I had a plywood (rather than a concrete) subfloor.

My question: is the warning I read on the website (which I can no longer find) too absolutist? Should subfloor moisture level be checked in all situations, in all places? Perhaps it's common practice to skip the moisture check in my area - because it's never a problem - or perhaps the guy doesn't know what he's doing. I would appreciate your advice.

EDIT: Forgot to add that I'm installing solid planks over plywood (on 1st and 2nd floors), not engineered or laminate.
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Old 07-12-11, 06:22 AM
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I don't install floors for a living but I can understand the logic of your contractor. Personally, I would be more concerned about making sure the planks had time to aclimate to the interior conditions of my house than the moisture level of a plywood subfloor above the ground floor.
Old 07-12-11, 06:31 AM
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I think you misunderstood or mis-remember what you read. For installations above grade, such as yours, allowing the flooring to acclimate by storing it briefly in the areas where it will be installed IAW manufacturer's instructions - inside the house - should be all that is needed unless you have a known moisture problem. Above grade, you're dealing with hunidity. At or below grade, ground moisture infiltration is a problem.
Old 07-12-11, 07:37 AM
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Join Date: Aug 2008
Location: USA
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Thanks for your responses. The advice given on the website definitely concerned subfloor moisture testing. I was able to find it again if anyone's curious: link

Obviously, that's just one person's opinion. If skipping the moisture check isn't that unusual, I'm glad to hear that.

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