HELP!!! Hardwood Floors Cupping

kathy50January 27, 2011

We noticed about a year and a half ago that our hardwood floors were cupping. (The house is 2 1/2 years old). The builder came back and we have slowly tried to find the reason for the cupping. We are left with the possibility that the wood was wet when delivered and installed wet. Of course the wood company denies this. The question is - now that the wood has been in the house for 2 1/2 years, if we sand and restain will the floor cup again? Is the wood now dry and sanding will even the wood out and solve the problem? The problem is with the floors on the entire first floor which would require us to move all the furniture out and move out ourselves. We will do this but would hate to think that this could happen again. Thanks for any insights.

Kathy

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boxers

Cupping is a sign of moisture. You have to find the problem or you will have the same result. You have moisture under the slab, a water leak somewhere or standing water. You have to cure the problem before adresing the hardwood. 2 1/2 yrs is a long time but I've seen jobs where when the moisture was taken away the wood slowly settled down.

    Bookmark   January 27, 2011 at 1:57PM
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woodfloorpro

Cupping is a sign of moisture from below. The bottom of the wood is moist and expanding more than the drier top, hence a cup shape. The fact it is over your entire floor would indicate you have poor moisture control in your basement, crawl or slab. You did not mention what is under the floor.

In 35 years I have never seen wood delivered wet, that is above 6% moisture. I have seen it become wet. If the floor was installed wet you would have gaps, not cupping, between the boards as it would shrink as it dried out in your climate controlled environment.

    Bookmark   January 27, 2011 at 4:00PM
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kathy50

We have had several floor experts look at the floors and crawl space. They have found no evidence of excessive moisture, mildew, leaks or water. We did ,however, discover that the original humidifier in the house never worked. After a rainy fall, we noticed the cupping. Could the rainy seson and the lack of humidity inside the house be a cause of the cupping. Do we need to install fans in the crawl space?

    Bookmark   January 27, 2011 at 5:34PM
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kathy50

We have had several floor experts look at the floors and crawl space. They have found no evidence of excessive moisture, mildew, leaks or water. We did ,however, discover that the original humidifier in the house never worked. After a rainy fall, we noticed the cupping. Could the rainy seson and the lack of humidity inside the house be a cause of the cupping. Do we need to install fans in the crawl space?

    Bookmark   January 27, 2011 at 6:55PM
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woodfloorpro

Crawl spaces are notorious for moisture problems. The best are now being built with climate control. Many have problems caused by settling of the fill allowing water to drain into the crawl or downspouts not directing the water away from the foundation. We find inadequate ventilation on most. Often the ground cover (6mil.) plastic is torn up by the trades and not repaired. In our area open soil in a 1000' crawl can release up to 8 gallons of moisture a day and much of it goes up into your floor. In other words there are a host of potential issues.
The houses humidifier is important to help keep the floors from drying out in the winter but is not the cause of your current issue. The humidity level ideally is within 35 - 55% range year round.
You need someone to seriously address your moisture problem. I do not feel those who have looked at it really know what to look for.

    Bookmark   January 28, 2011 at 11:28AM
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brickeyee

Wood changes size and shape with moisture movement in and out.

It never stops, no matter what finish is applied.

Chapter 3 of the USDA Wood Handbook covers wood movement with moisture.

Figure 3-3 shows how shape changes.

Here is a link that might be useful: Wood Handbook, Chapter 3

    Bookmark   January 29, 2011 at 11:10AM
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livingdesignbuilders_gmail_com

I concur with the previous posts - sounds like moisture entering the wood from below, which would cause the long edges of the boards to lift - and create a cupping condition. You might also check to see that there is proper space for the floor to "Move" around the perimeter. If you pull up a section of shoe molding or a section of base trim around the perimeter, you want to make sure that there is an expansion gap that the wood can move into during the high humidity portions of the year. If the wood binds between the plates on either end of the floor, it could cause an increase in stress (compression) of the boards and result in a cupping action. (I doubt this is the case though) My money is on excess moisture coming from below!

    Bookmark   March 7, 2011 at 8:32PM
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brickeyee

"You might also check to see that there is proper space for the floor to "Move" around the perimeter. "

Unless the floor is engineered and moves as a single large piece (floating) the movement at the perimeter is no larger than the movement in the field.

Cupping depends on the grin orientation in the wood (how it was oriented in the tree) and how much the moisture content has changed since installation.

    Bookmark   March 8, 2011 at 8:49AM
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