How to Fix Hardwood Floor Problems: Cupping, Crowning, Chatter, and More

cupped hardwood floors

Knowing how to quickly identify and efficiently fix common problems with hardwood floors is an important skill to have, especially if you are a hardwood floor contractor.

Here are some of the most common problems that occur while installing hardwood floors––including cupping, crowning, and squeaky floors––and instructions on how to fix them.

How to Fix Cupped Hardwood Floors

Cupping means that the wood that is raised on the edges of each individual floor board. The center of the board dips below the edges. This makes the wood appear to be in a “U” shape. (See the picture at the top of this post for an example of a cupped floor.)

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Typically, cupping is a problem that stems from excessive moisture. Anything from pipe leaks to a still-wet concrete slab to improper HVAC usage can cause cupping. Wood is hygroscopic, meaning that it absorbs and releases moisture. When one side of the floor is exposed to excessive moisture, that side will expand, causing the whole board to warp away from that side. The sides of the boards curl up, resulting in the characteristic “U” shape of a cupped floor.

Sometimes, cupping is a result of normal humidity shifts that occur due to changing seasons, and will correct itself naturally as the seasons change. However, if the cupping is due to an underlying moisture problem, the floors will stay in this position until that problem is corrected.

To fix the issue of cupping the first and most crucial step is to assess the moisture problems. Take the necessary steps to stop or correct the source of the moisture problem. Certain issues that can cause cupping include wet mopping the floor, plumbing leaks, a damp subfloor, and the environment fluctuating outside of a range of relative humidity (RH) that is acceptable for the floor.

Once you find the source of the moisture and correct it, verify that the floor straightens out within the next few weeks. If not, it could be permanently damage and in need of sanding and refinishing or, in some cases, board replacement. DO NOT sand a cupped floor. Sanding a hardwood floor while it is still cupped will result in a problem called “crowning.

How to Fix a Crowned Hardwood Floor

A crowned wood floor is another problem that is usually the result of a moisture issue.

Crowning is typically a problem that is a direct result of cupping. Crowning is characterized by wood that is raised in the center and dips down on the long edges of the planks.

This issue can either come from a moisture issue that is affecting the center of the planks, or from sanding a floor that was cupped and still had moisture issues. In the latter case, a cupped floor was sanded flat, but once the moisture levels return to an acceptable level, the edges of the plank were sanded down below the center.

To fix a floor with crowning, you must find and correct the issue that is causing excessive moisture, which can include leaks, wet slabs, or improper HVAC usage. If you need a crash-course on testing moisture the content of a hardwood floor, check out our guide.

Once you are sure that the moisture problem has been corrected and the moisture content of the floor has returned to the right level, monitor the floor for a few weeks to see if the planks return to normal. If not, the boards must be sanded and refinished or, in some cases, completely replaced.

Halo Effect/Picture Framing in Wood

Halo Effect Hardwood Floor

Picture credit:

The halo effect (also known as picture framing) is when the edges of a room appear to be a different color than the center.

The most common reason for the halo effect on a hardwood floor is when different sanding approaches are used in the same area. For example, picture framing could result from using 60, 80, and 100 sandpaper on the big machine, but using 80, 100, and 120 with the edger. Improperly blending the field of the floor with the edges can result in the hardwood floor stain absorbing differently, leading to this dreaded “halo effect”.

The fix for the halo effect is to re-sand the floor using compatible sanding schedules with the big machine and edger, ensuring that you effectively blend the field of the floor with the edges. Water-popping the floor can also help the stain absorb evenly.

How to Fix Chatter Marks in Wood

Chatter marks are repeated imperfections on the floor that are between 1/2″ and 3/4” apart.

They are traditionally caused by some sort of failure in the big machine sander. Bad sandpaper

Lagler Trio

A multi-disc sander like the Lagler Trio can help you get rid of chatter marks.

alignment, uneven wheels, incorrect drum pressure, imbalanced drums, loose V-Belts, or failed

bearings are common issues that could produce chatter marks on hardwood floors.

The best way to prevent chatter marks is to make sure your big sander is operating perfectly. You may have to take it to a repair shop to have it serviced.

If there are already chatter marks on your floor one great way to fix them is by using a multi-disc sander like the Lagler Trio. The multi-disc sander is specifically designed for finish sanding. It is powerful enough to remove cross grain scratches but will not change the wood floor’s topography.

Read our blog about getting rid of chatter marks for more details about this issue.

How to Fix Squeaky Wood Floors

Hardwood floors with significant movement or noises could be the result of several factors.

If the floors were installed with improper nailing schedules or the incorrect adhesive, they will be loose and cause noise. If the subfloor is inappropriate for the wood floor being installed that could also be the cause the noise or movement.

Fixing the problem of movement and noise could be simple like adding adhesive to the problematic floor boards or top nailing. However, if the problem is extensive, it may be necessary to reinstall the entire floor.

If you have any additional questions regarding these common problems with hardwood floors, feel free to contact us at (800) 737-1786 or

14 thoughts on “How to Fix Hardwood Floor Problems: Cupping, Crowning, Chatter, and More

  1. Valerie Ewing

    We have an open floor plan with all new hardwood, I noticed the cupping right away, it’s getting worse. Why is this happening and what can I do about it. We are sick over it as we spent quite a it of money on this renovation. Please help

    1. Caran Baxter

      Hello. Sorry that you are not happy with your new wood floor. There are many variables that lead to a wood floor cupping, but they all have one thing
      in common, Moisture. I would definitely have your installer measure the relative humidity of the facility and moisture content of the wood floor
      and subfloor.

  2. Amy

    Is there anything I can do to reverse cupping in a two foot square area where a plant leaked water on the hardwood floors?

    1. Caran Baxter

      Hello. Thanks for the question. First and foremost address the source of the moisture and remove it. Unfortunately once the flooring has
      cupped the only real solution after it dries and reached Equilibrium Moisture content is to sand it.

  3. David Land

    I have a new (6 month old) on-site installation of 3/4 inch hardwood flooring that is cupping. Moisture is at 4.5%. I called the company who installed the floor and they said the moisture level was too high. I highly disagreed with them, as I am reasonably certain it should be at or about 6%. Being present for the installation, pieces of flooring were ripped and gently hammered into place, but very tight. Could the low moisture content or the tightness of the installation be the culprit for this issue? And it is not throughout the entire 1600 sq. ft. of hardwood floor. Most of this is where new wood was installed.

    1. City Floor Supply Post author

      Hi David,

      We’re going to need a little more info in order to properly answer your question. What is the species, where are you located, how wide is the flooring, and is this material solid or engineered? When you say that the moisture is 4.5%, what was it measured with? What is the relative humidity? Is this install “toothed” into an existing floor?

      Sorry for all the questions, we just need a better idea of what’s going on.


  4. Laura Smith

    I am curious, my installer did not acclimate my 3/4″ white oak stained on site wood floors. They brought them over and installed the the next day. They did go around with a moisture meter on my sub floor and the new flooring and said that they were close enough to each other that there would be no issue.

    House is a 1960’s ranch with crawlspace. We recently replaced all visqueen vapor barrier and floor joist insulation

    Here we are with cupped floors They cupped shortly after install and have not gone down 6 months later. They specialize in wood floors so that is why this is all so weird.

    They claim that 5-7 days acclimation is not needed yet here I am with cupped floors.

    Any ideas?

  5. Robin Schemmel

    Hi. I have a home in Florida that I renovated and added on to.I did the usual 3/4 plywood flooring in the new construction and in the existing rooms I leveled the floors and in order to make sure I had a nice flat surface I first put 15# roofing felt first,then put down 5/8 plywood,once I had all of the floors on the same level and vapor barrier installed,I then installed with screws 1/4″ birch plywood then again added a the vapor barrier. I then installed prefinished Bamboo flooring with flooring cleats bought at Harbour Freight.I spaced the cleats approx 5″ apart and spaced them from the ends approx 4 inches i used 6 cleats per piece.The flooring has been installed about 9 years it was acclimated for 1 month in a/c .Within the last 2 years I noticed in the kitchen after,a pipe leak that I had some spots at the cleat points, this started within about 4-6 months after the leak and initially at the cleat points.Then over the last 1 to 1.5 years the kitchen floor has cupped terribly and has turned very dark grey and has gone under my cabinets and has now within the last 3 months started to spot at the cleats in a bedroom which is separated by a wall and is also the new construction,and also in the closets.What is so strange is the very furthest bedroom which is seldom ever used and is also in the new addition and separated by a hall and is about 20 feet from the kitchen, is starting to show alot of these spots at the cleats .The dining room is part of the continuous kitchen floor and has no spots ,neither does the living room which get the most use ,other than the kitchen also the hall does not have any signs of spotting anywhere which may be because it had to be glued because it had to be leveled.My last bedroom in the old part of the house approx 8′ from where the leak was has no spots.I am very perplexed and I am hoping that you may have some insight as to why I am having this problem?I also keep the a/c on and set at 73 during the summer my house barometer reads normally 36-40%..I have submitted a claim with the place I bought the flooring with as the flooring has a 10 year warranty .Please help as I am now trying to figure what type of flooring I should consider replacing the bamboo with.Do you recommend cork backed flooring? Thankyou Robin

    1. City Floor Supply Post author

      Hello Robin,

      Thanks for your question. We would have an NWFA certified inspector come out and have a look. It’s difficult for us to deduce what’s happening. Really sounds like an onsite inspection would be best.

  6. isaac jacobs

    I have a couple of 3-1/4 wide oak boards cupping from a water leak. Once dry what’s the best way to sand the seam down where it cupped, belt sander with the grain or orbital sander? What grit sand paper?

    1. City Floor Supply Post author

      The high edge of the cup is typically sanded flat. We would then recommend cutting that floor at a 20-30 degree angle then straightening. The grit depends on the floor. The first pass should get the high edge even. You also have bevels to deal with.

  7. Roy McKinney Jr.

    I have a hardwood floor that appears to have waves in it it almost appears to be buckling any advice on how to fix

    1. City Floor Supply Post author

      Hi there, it sounds like there might be an underlying moisture issue that needs to be corrected, possibly in the subfloor. If you give us a call at (800) 737-1786 with more details we may be able to help you troubleshoot.


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