I am putting down 1200 sq ft of character grade maple, 4 inch wide, on a floor over an unfinished basement. We have hvac. Had a large rain and some water got into the basement through some sleeves through the foundation (that I will be fixing). I checked the subfloor moisture content, and in some places it is at around 10%, but some places over where the water got in and sat, is up around 14%. The flooring moisture content is between 6 and 8 %. I thought I had read that the difference in moisture content needed to be no larger than 2-3%, but looking at the site from the wood flooring association it just mentions the moisture content of the subfloor when wood should be delivered (and 14% is acceptable).

So, to cut to the chase, should I be worried, and make sure I wait til the subfloor is down a bit (maybe running a dehumidifier in the basement)? I still have a few weeks anyway, so it may not matter. I will be using probably 30# felt under the wood.

Ron

Both NOFMA and the NWFA recommend no more than a 2% variance in the moisture content between the subfloor and SOLID (not engineered) plank flooring. With solid strip flooring, a 3 to 4% moisture content variance is supposedly allowed. IMO, any wood subfloor at 12% MC and over is suspect and will probably cause problems. This is from NOFMA's Installation Manual:

http://www.nofma.org/Portals/0/Publicat ... Floors.pdf

"The average moisture content
of framing members and subflooring should be
below 12%-14% before delivery of the flooring. Moisture
contents above 12%-14% can cause moisture related
problems."

NOTE: It says below 12 to 14%. Not 12 to 14% is OK. Big difference.

Thanks Gary, I obviously missed that key word "under". How long will it take to get back down, if I keep the basement dry? Would it speed things along if I ran a dehumidifier in the basement?

In one week it got better, but still not acceptable. I'm a one man builder on this house, and I am working to get other jobs done, so I'm a few weeks out.

Ron

Fans and dehumidifiers will speed things along but won't help unless the leaks have been stopped. If it's plywood, that may take a few days more than OSB. Reports have shown plywood subfloors hold moisture a little longer than OSB. How are you determinimg the MC? Are you using a pin style moisture meter?

Yes, pin moisture meter (lignomat mini). Plywood subfloor. I am plugging all known ways for water to get in. The sleeves had never been sealed, so that was easy enough. Had another leak on a wall in the basement, won't know if it is fixed til the wall dries out more.

Thanks again for your help. I've got a few weeks yet, probably 3 or so.

Ron

One of those electric heaters right near the really wet spot with a fan blowing the heat down on the wood subfloor.

More then one dehumidifier in the basement!!! Fans everywhere to circulate the dehumidified air.

When that meter reads within 2% your good to go, but not until then, or your floor will cup.