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Q & A: Wood Floor “Cupping”?

Question by Kelly R: Wood Floor “Cupping”?
My new wood floor is “cupping” according to a handyman who observed it at my home. The floor isn’t even a year old yet. I had an addition put on and the builder either installed it wrong or maybe something is wrong with the wood floor. It is oak flooring planks 3 3/4. It wasn’t cheap flooring and purchased through a reputable carpet flooring store.

What do I do? Will it uncup as the weather gets cold and the air dry’s out from heating, should I have the builder replace it? What a mess! Did the installer just fit the boards too tight. If I don’t do anything will it damage faster with the slightly raised edges?

I haven’t talked to the builder yet.

Thanks for your help!
It was done on a sub wood floor…not a slab. It was alos done in the winter so I think that maybe the flooring hadn’t warmed up enough and the temp in that room was in the 60’s. It is also cupping up down the long side length of the boards. Not on the ends. It is not hugely dramatic but still has a ripple look to it.

Best answer:

Answer by spongeworthy_us
Could they have gotten wet or is the humidity too high in your home?


Once the source of the moisture is controlled, cupping can usually be cured. The floor may improve on its own as it dries out over time. Other times, fans may be needed to speed the drying process. Once the moisture content has stabilized, the floor can be reassessed.

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6 Responses to Q & A: Wood Floor “Cupping”?

  1. theminnguy

    This may not be judged the best answer, but it is the correct one: CALL THE BUILDER! The work should have a one year warranty. If the builder denies warranty, saying it is normal or that you caused the damage yourself, then you pursue it. Many environmental conditions effect hardwoods, one of the most common in my experience is the humidity is set too high on the humidifier. This is not something to wait on, the cost to refinish the floors can be expensive, and depending on the severity, may be the only option. Call the builder.

  2. crystalshannon516

    Call a water restoration specialist, such as servicemaster or serve pro. They’re technicians are trained to read these moisture meters and correct the moisture problems. If the flooring has been wet for some time damage is unfixable without sanding and refinishing. I have seen your problem so many times. If the moisture isn’t taken care of first your problems will persist, and could even create a mold issue between your flooring and subfloor or even under your home. I would look into this issue.

  3. Drew2U

    I have the same problem as you do. We just bought a house and it did it. I think we left the door open that is next to the floor for cool air to come into The house and the moisture made it do it. I have noticed that the cupping has gone down some but is still very bad. We are going to get our repair man to look at this in the very near future.

  4. hwfiedler

    If the addition was built on the side of an existing structure it should have been done in such a way that water was blocked from the underside. Well dried lumber properly installed and under conditions of proper humidity should not warp and should not be affected by normal expansion & contraction. If the cupping is not TOO bad after a year a refinisher could sand it smooth and level…after the builder corrects the source.

  5. Matrix

    I’ve been building houses for 30 years and have never had that problem. It sounds to me like the wood wasn’t dry enough to install or at the mill the boards weren’t milled with the natural cup of the boards up rather than down.

    Rather than have the whole thing taken up and reinstalled, I would suggest to live with it for a few years and then have it sanded, stained and varnished. Get the builder to atleast pay for 1/2 of the expense.

    Good point by Mary, is the flooring over concrete or plywood?

  6. Mary N

    I can help you but you will have to reask the question so i can answer. My husband has 30 years experience in the wood flooring business but he says he needs to know if it is on concrete or a wood sub-floor. And also if it is cupping downward or upward? THis info will determine the most likely problem.

    OK with the new info my husband says….

    There is not a proper waterproof membrane between the sub floor and the flooring. You have a lot of moisture under your house that is coming in. If the floor cups upward ( with the hump rising upward ) the moisture is coming from the top. If it cups downward ( with the hump going down ) the moisture is coming from the bottom.

    This needs to be corrected or it will do it again and again.

    You can go to a local hardwood store and rent a moisture meter real cheaply or have someone come out and read the moisture for you. Your moisture level needs to be 10 % or less.

    Then you will have to fix the source of water underneath before you can fix the top wood. It could be a builder fault or an installer fault. It could be a matter of just fixing the landscaping outside to cure the problem. But the source of moisture must be fixed.

    Gaps are normal due to humidity changes. Cupping is not.

    You cant fit the boards too tight. This would cauese problems in your walls instead.

    They do not sell boards with bad moisture content. They are all kiln dried. Your flooring should be put in the house to let it acclimate 72 hours prior to installation.

    It is possible , depending on what you find out, that someone is liable for this problem.

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