Can Wood Floor Cupping Be Fixed?

You’ve had a beautiful hardwood floor installed in your home. But after a while, something doesn’t look right—or feel right. Maybe the floor seems “wavy” or even rippled. You may notice small, raised ridges along the edges of some of the planks in the floor.
hardwood floor cupping problems
What’s happening to your previously gorgeous flooring? And can it be stopped?

Cupping is one of the unfortunately common issues that can plague hardwood floors. It can happen to most types of wood, and it’s often the first observable sign your floor is being affected by moisture.

Since wood reacts to moisture so easily, floorboards can warp as they react to the change in their internal moisture content (MC) after the floor’s installation. But if you catch it early and can address the moisture issue, there is hope in getting your floor back to normal.

Here’s what you need to know.

How to fix hardwood floor cupping

  1. Make sure you have a reliable wood moisture meter so you know how much the wood moisture content has risen or can identify wet problem areas. While several types of meters are available, few allow for multiple tests in multiple areas over and over without damaging the wood. The Wagner Meters Orion® moisture meter line uses electromagnetic wave frequency (EMF) to measure large areas.
  2. Determine where the moisture is coming from. As referenced above, is the cupping uniform and seasonal? Is it confined to one area? Has the floor been installed recently, or could there be more moisture in your crawlspace or basement than in the living space?
  3. Get a dehumidifier, especially if you have a basement or an area of the house that tends to be more humid than other areas. If you live in a place with humid summers, you may just need to run it seasonally to keep your wood floors in top shape year-round. The key is controlling the climate in your home, keeping it as consistent as possible.
  4. Maintain your floor properly, using the right cleaning methods and products made specifically for wood floors. Always dry spills thoroughly, and routinely check wood floor areas around sinks, dishwashers, bathtubs, and other areas more likely to have leaks or spills.
  5. After a significant leak or spill, especially if water or other liquids have had time to absorb into the floor and subfloor, you may need to contact the professionals for high-powered drying equipment. A dehumidifier is great for humidity in the air, but wet warped floors need a more direct and aggressive approach to avoid lasting damage.

What does cupping look like on a hardwood floor?

what does hardwood floor cupping look like
When moisture interacts with a hardwood floor, the side of the boards closest to the moisture expands. This expansion can be in the form of cupping (the center of the board is lower than the edges) or crowning (the center of the board is higher than the edges). Both situations, although different, are both due to a moisture imbalance in the boards caused by either the addition of moisture or the extraction of moisture from the floor.

Sometimes the early stages of cupping can be noticed when light comes in from a window and reflects onto a wood floor. You can see small shadows where the edges of each floorboard are slightly higher than the middle.

Why does cupping happen?

In short, moisture. Wood, even when it’s treated and sealed, is still a porous, fibrous material. It can still react with the moisture content (MC) in the air around it. Materials like wood will balance (equilibrate) its MC with its surroundings, similar to the principle of osmosis.

So if the air is humid, the wood will absorb more moisture from the air and it will swell. If the air is dry, wood fibers will release some of its moisture back into the air and it can shrink back down.

It’s most common for moisture to enter the floorboards from below, through the subfloor. This is why the bottom of the board swells and makes the edges curve upward into an almost wave-like pattern.

Cupping can happen even to a flawlessly-installed wood floor, depending on the conditions of the building and the environment. However, several common situations that are known to cause cupping can be addressed, and can even be reversed.

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What are the common causes of cupping in flooring?

  • Change in the amount of moisture in the air (relative humidity). If you live in an area with humid summers and dry winters, or even vice versa, your wood floor can react to the changing amount of humidity in the air. It expands during one season and contracts in the other.
    If cupping is happening in a relatively uniform manner throughout your house, and the degree of cupping is not drastic, this is likely the cause.
  • Subfloor moisture. If there is excess moisture in the concrete slab, crawl space, or basement below your wood floor, this can cause cupping. This is especially common with new construction if the floor is installed before any type of HVAC is running within your home. It can also happen later if your basement or crawl space harbors more humidity in general.
  • Leaks or spills. Cupping due to leakage will usually be confined to areas around sinks, dishwashers, etc. If a leak is slow or small, the cupping can occur gradually and you may not notice it until it has gotten worse. Sudden leaks or spills can cause cupping if they aren’t cleaned up quickly or thoroughly, or some moisture is left behind.
  • Improper care/cleaning. On a similar note, especially when cleaning up larger leaks and spills, cupping can come about if any moisture is left behind after cleanup. What’s more, unless proper cleaning techniques and supplies are used, further damage could result as well.
  • Improper installation. If a hardwood floor is installed before a subfloor is properly dried, or before the floorboards reach an equilibrium moisture content (EMC), such as before the inside of a building’s air is conditioned, there is a chance for cupping later on. As furniture and people begin to inhabit the area, it will bring about a new level of moisture and temperature to the air. You want to ensure that moisture levels between the subfloor and the finished floor have reached proper EMC for the long-term. And to make absolutely sure the moisture readings are optimal for beginning the installation, you want the most accurate moisture measurement tools possible.

If cupping is discovered in an already-installed hardwood floor, can it be fixed? Does it need to be replaced?

In many cases, if cupping isn’t severe, the issue can be fixed once the moisture issue is fixed. Since the process of cupping is the wood reacting to moisture, if the wood’s moisture level returns to the proper equilibrium, the cupping can resolve.

Depending on the type of moisture issue, however, will determine how easily it can be fixed or how much effort it will take.


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What happens if cupping doesn’t get fixed?

Besides the visible warping of your hardwood floorboards, the floor could fail. The cupping could continue to worsen and create gaps between the boards. If/when the relative humidity drops, the boards may not go back to their original shape and can buckle away from the subfloor, or even splinter and crack.

The big issue, however, is still moisture. If the cupping in the floorboards doesn’t go away, it could mean that the underlying moisture issue was not properly addressed and still needs some attention. While cupping can remain after a severe event like flooding, persistent cupping is worth investigating. Prolonged moisture issues can lead to many types of flooring failures, so it pays to be safe.

What NOT to do when you notice cupping in your floor.

One rookie mistake is to simply sand the floor down until it’s level again. But once again, the moisture problem that caused the cupping has not been dealt with. For example, if the cupping happened due to humidity from an especially wet summer and you sanded down the cupped areas, when the air dries out the wood can warp the other way, causing crowning.

You also don’t want to assume your floor has already failed. There is still hope! Many moisture issues can be fixed through household climate control, taking moisture readings throughout the house, or seeking out undetected leaks or spots where moisture could creep in from other areas.

To avoid these mistakes, there is a way to test for a change in your home’s ambient conditions over time. Relative humidity data loggers can tell you what has changed in ambient moisture levels when it changed and for how long. This information can help you determine what actions to take with your flooring.

The FIRST thing to do when cupping is discovered.

If nothing else, the appearance of cupping tips you off that your hardwood floor is susceptible to moisture problems. Even before you call a professional, if you have a reliable wood moisture meter you can use to take multiple readings throughout your home, you’ll have a much better idea of what kind of situation you have on your hands.

You might be able to figure out how to remedy the situation yourself if you find it’s due to humidity in the air or a leak or spill. And if you do discover it’s a serious issue, you’ll have much more precise information to give the professionals so they don’t have to spend as much time (and your money) doing detective work.

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Safeguard your beautiful hardwood floors with moisture measurement you can trust. Learn more about how Wagner Meters’ Orion® moisture meter line is easy to use while providing the most accurate readings available on the market.

Avoid moisture related issues with an accurate wood moisture meter to test your hardwood flooring.

Buy an Orion Meter

Last updated on June 23rd, 2021

50 Comments

  1. Emily says:

    My husband and I just bought a cute 100 yr old house a couple of months ago (during the summer it is now winter) and the two upstairs rooms both have cupped floors.

    There is evidence of previous water damage to both rooms. But both floors dont show much water damage (beyond the cupping.) We have so far been unable to determine where water could have entered the room (based on the damage.) So im not so worried about a major water leak (there is also no plumbing upstairs of any kind.)

    The downstairs wood floors are beautiful and have no evidence of warping Im hoping you have a solutions that means we don’t have to replace the floors.

  2. snyder says:

    Hi. HNY! About 18 months ago 1 x 6 select t&g oak flooring was installed in my home. This was recently milled stock. The house is on raised brick piers. The soil under the house was covered with a heavy plastic which partially extends up each pier, one year ago. Plan is to resand the floors in late January. Is there a better way? Thanks.

  3. Steve Crisby says:

    Dishwasher leaked – My fault but after watching fir leaks when doing final install of dw in place I loosened the supply hose The slow drip wasn’t discovered until floor boards were cupping. Guessing it dripped for 2 weeks enough to when discovered there was a pint of water in crawl space. Cupping is such you almost need look or feel for it. No visible water staining on joists in crawl space. The cupped board area is maybe 4 x 4 foot area. mostly. We fixed leak. Ran fan over the top of the area for days. Set up a dehumidifier to try move air and dry out crawlspace. How long do we wait to see if the area increases or improves more? I believe it is improving but after a week I can feel barefooted. Not when wearing shoes. Visible when look for always. Hard to notice unless looking for. Thought comments appreciated greatly

    • Jason Wright says:

      Steve,

      I have had experience with this first hand. It all depends on the time of year and how badly the floor was damaged. It doesn’t sound like its that bad indicating to me it should be flat within 6 months. Hope this helps.

  4. Dominic says:

    Hey Jon hoping you could give me some much needed help. My apartment has sealed wood floors but it’s those that snap in. The other day as stupid as it’s gonna sound I fell asleep for only a few minutes less than 5 as I was running a bath but when I woke the tub over ran and my area rug was soaked. Of course I jumped up, turned off the water and opened up the drains and scrambled to get a mop towels bed covers anything to get the water. By the time I got rid of all the running water everywhere, I removed the area rugs (I have two as I live in a studio apartment). The one underneath my bed which was furthest from the entry of the water and got pretty wet doesn’t have a protective pad underneath it but the area rug that got hit by most of the water and because the pad underneath (which ironically enough I bought in order to protect the floors) was made of felt it absorbed a lot fo the water and cause some cupping in three areas. Everywhere else is fine, underneath my bed looks normal, and even the floor right in front of the bathroom is perfectly fine, it’s just the area where I had the protector pad and area and it’s only three raised sections. So here are my questionns I’m hoping you answer:

    1) will this go away over time? I understand that it will definitely take weeks if not months for the moisture to dry out. The water and area rugs where there for all of ten minutes if that and nothing else is leaking.

    2)I have replaced the now dry area rug but should I remove it and let it breath? Should I place a new protector pad?

    3)Assuming it will dry over time, how much time would you guesstimate for one off time?

    Just to give you an idea of the climate where am in, I stay on a 9th floor with 5ft height west facing windows that span 80% of wall so lots of sunlight and I’m a beach city in the southern California, so again lots of sun. Any helpful advice or diy tips would be suuuuuper appreciated. Thanks!

  5. Leo Landry says:

    Jason,
    My new 6” white oak floors look just like the picture in this web site.
    I’m in the process of dehumidifying my crawl space.
    How long does this take? My dehumidifier is showing 40 % . But, I’m guessing that’s the air and not the wood.
    Am I looking at weeks? Or months? To go back to normal? Thanks

    • Jason Wright says:

      Leo,

      Thanks for writing in. In a situation like this, there are too many variables to narrow down a time frame.

  6. Heather says:

    Hello,
    Our new home was finished about 5 months ago. After about 2 months of living in the house I noticed the Red oak floors were cupping. My builder went under the house and didn’t notice anything. Two months later, the cupping was getting worse. Apparently there was inadequate ventilation and one section of the insulation was completely wet. That was removed and we just had a dehumidifier installed under the house. I just noticed a small area where about three floor boards are also crowning. How can I have both cupping and crowning in different spots at the same time? I’m so bummed since this is a brand new home. I’ve also been running a dehumidifier in the house and the relative humidity has been around 50 or 55. I live in South Carolina and we’ve had a very humid, wet summer. If the crowning doesn’t improve, is it possible to only sand and restain a small area? I really don’t want to have to sand my entire house. My floors are stained with Jacobean stain. How long should I wait before making a decision to sand? It is finally cooling off and we should start using our heater within the next month.

    Thanks,
    Heather

  7. Helen Cassidy says:

    We installed hickory 5″ x 3/4 ” think floors in our Maine home. The floors are cupped and failing. We have a crawl space under the house. We sprayed the entire crawl space with the foam insulation before we installed the floors. The contractor that installed the floors did not deliver the flooring until the day before they installed the floor. We plan to replace these floors. The floors are only 5 years old. My question is what can we do to prevent this from happening again. Should we spray foam insulation the actual subfloor under the house? We did a reading on moisture under the house and it is dry. Where could moisture be coming from? It showed no moisture with a moisture reader. We had a company come out and test the subfloor. They got the same results. No moisture. Could it be that the contractor didn’t have the wood acclimate to the space? We are fearful that this could happen again. We have wood floors upstairs and have had no issues up there. We live where we have ledges all around us. The house has concrete stem walls. Remember we sprayed the entire floor with the foam. Please help us. How long does the wood flooring need to be in the house before it can be installed? Does the flooring need to be out of the packaging? We also close our home in the winter. We live in Florida in the winter. We keep our heat set on 50 degrees while we’re gone. We have tried dehumidifier under the house in the spring. Everything we have done has not worked. Help!

    • Jason Wright says:

      Helen,

      It’s possible that it wasn’t acclimated properly. Acclimation is when the flooring had reached the conditional moisture context where it will be installed. Wood is gyroscopic and will lose or gain moisture depending on its conditions.
      It may be best to visit http://www.nwfa.org to get installation guidelines for your next floor. Hope this helps.

  8. Christy Taylor says:

    We installed a new ac 3 1/2 ton 2 phase variable speed unit with heat pump and has a dehumidifier. We live in a pier and beam house in East Texas. 3 months after installing the ac our laminate flooring has started cupping and paneled walls buckling we keep ac around 71 and moisture is usually around 60 how can we correct this problem when we redo our floor should the AC contractor known this could of caused this. Floors are 7 years old

    • Jason Wright says:

      Christy,

      It’s hard to tell what is happening with your laminate floor without gathering more information. It may be best to contact NWFA.org to get an independent inspector to review your floor and determine the cause. I hope this helps.

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