Cupped Hardwoods

hgxxAugust 26, 2012


We have been remodeling a house for the past 2 1/2 months. We had 4'' white oak hardwoods installed in about 1900 sqft of the house. The wood sat in the house for 12 days, bundles in every room, to acclimate. Shortly after they were installed, sanded, stained and one coat of poly applied, they cupped. We live in the Southeast with high humidity and the house has a crawl space.

The house has ventilation vents, poly covering most of the crawl and no signs of standing water. We have opened all vents, installed 3 ventilation fans and the moisture content hasn't really gone down. One guy came out and wanted to remove all of the crawl space insulation and put in new poly for $2800...seemed a little steep.

The installer thinks the floors will "lay" down one the crawl is dry. I'm not convinced and we are eager to get into the house. I've read a lot about not sanding cupped floors but it is very tempting to sand the floors and move in. The moisture reading on the subfloor is 12 to 14%. The moisture reading in the insulation is 22 to 30%. The moisture reading on the hardwood is 5 to 7%.

Looking for some sound advice.



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So sorry this has happened! I know it's frustrating, but waiting until you've corrected the underlying problem and allowing the wood to dry out as much as possible is key before you start sanding away.

When you say the house has ventilation vents and that they're open, are you speaking of the ones in the walls of the crawl space? If so, you might try closing them and placing a couple dehumidifiers under there to pull the moisture out. Just running fans likely won't do it.
In the humid SE, the hot air coming in from the outside hits the colder air and/or components located in the crawl space and moisture/condensation results--especially if your A/C system is under the house vs in the attic. We just went through this with our house in the SE as well. Luckily, our HVAC guy had come out to evaluate for our expansion and noticed the condensation issue before any damage was done.

I can tell you that we had a similar problem with cupping in our last house due to moisture. We fixed the underlying problem (blocked vent) and ran 2 dehumidifiers in the affected room 24/7 for about a week. The cupping diminished significantly.

Hope this helps & good luck!

    Bookmark   August 28, 2012 at 12:39AM
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Thx for the reply! I am talking about crawl space vents. Every "expert" I've spoken with has suggested opening the vents and installing vents fans to get the air moving. I've considered doing exactly what your talking about with the dehumidifier. Had a guy look at it yesterday and recommended pulling the insulation out and running a dehumidifier in the house..seemed a little odd to put the dehumidifier in the house instead of the crawl??

    Bookmark   August 28, 2012 at 7:12AM
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The experts here on GW + my own experience is where I got the info on next steps for you. Here's a link to my post requesting help on the HVAC website.

Since we took the steps of closing the vents and running the dehumidifiers things have dried out considerably. There have been multiple posts on GW this summer about the very same thing happening all over the SE.

And here's a post talking about the vents with the fans and the different things that can happen if they run intermittently or if they run continuously. It seems as if that's a potential no-win situation.

I would save the money on the vent fans, use it to invest in a couple decent sized dehumidifiers, close the vents and run the dehumidifiers until they don't pull anymore water.

You may try posting on the HVAC board too. Have you checked on top of the main unit under the house to verify that you don't have condensation occuring? We saw it dripping from the ductwork when the HVAC guy came out, but if not for that we wouldn't have investigated further and realized that the entire top of the unit was covered in a huge puddle of condensation.

Hope this helps!

    Bookmark   August 28, 2012 at 8:54AM
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Also, I would imagine running one or two dehumidifiers inside the house wouldn't hurt either. I would think it would be a good idea as the water would be pulled straight out of the hardwood floors vs. having to be pulled back through the subfloor from underneath. However, the problem in the crawlspace has to be addressed or it will become a never ending battle of cupping floors.

    Bookmark   August 28, 2012 at 8:58AM
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Thx for all the info!

When I checked the crawl space, every piece of air duct and the air handler had condensation. Everyone suggested opening the vents to get air flow and said that would remove the condensation.

I tend to agree with your assessment. I have my HVAC guy coming out tomorrow to check on the issue. I'll post our progress.

Thx again!

    Bookmark   August 28, 2012 at 10:58AM
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" Everyone suggested opening the vents to get air flow and said that would remove the condensation. "

Only if the outside air is not humid.

If the surface of the duct falls below the dew point of the air condensation occurs.

Insulating the ducts has a better chance if the humidity outside is high.

    Bookmark   August 28, 2012 at 11:36AM
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Any updates, hgxx?

    Bookmark   September 6, 2012 at 10:21AM
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