Hardwood Floor Cupping – What To Do?

One of the most traditional and beautiful choices for flooring in any home is exposed hardwood. Hardwood floors have few disadvantages compared to all of the advantages they can bring to your home. Unfortunately, pitfalls happen even if the list of negatives is short. Cupping is one of those pitfalls. We have looked into everything about hardwood floor cupping so that if it happens in your home, you can be ready!

Like with most hardwood floor issues, cupping is caused by moisture. The moisture that causes this issue can come from several different sources. The cause of cupping can also be because proper steps weren't taken when the flooring was installed. Depending on the cause of the cupping, there are a few different ways to possibly fix it:

  1. Locate the source of the moisture and fix it.
  2. Consider sanding the cupped boards.
  3. Call a professional and consider replacing the boards.

Doing repairs on your hardwood floors can be a stressful and worrying situation. That's why you should make sure that you have all the information you can get before starting. Continue reading down below for an in-depth look at hardwood cupping and what to do about it!

A swollen hardwood floor after a week of outfall water from corroded water heater, Hardwood Floor Cupping - What To Do?

Hardwood Floor Cupping

Hardwood floor cupping is when the affected boards warp in a specific way. You can tell when cupping is happening because of the shape that the boards get. The edges will be raised slightly more than the center of the boards. This gives the boards a cup-like shape which is how this problem got its name.

What Causes Hardwood Floor Cupping?

Swollen and receding parquet after water leakage

Hardwood floors are very durable and resistant to most things, but moisture is not one of them. Moisture can affect boards in a few different ways, and cupping is one of the most common. Since wood is porous, it begins to expand once it absorbs enough moisture. The reason cupping happens is that the edges of the board expand before the center.

What Kinds Of Moisture Cause Cupping?

Any source of moisture can cause cupping if there is enough of it and it has enough time.

Moisture Under Your Floor

Depending on what is under your hardwood flooring, it can be possible for moisture to settle there. If you have a damp and humid basement or crawlspace, moisture can be drawn up from that. Another major cause of this is flooding. It can be easy for water to find its way between your hardwood and the flooring below it. The biggest problem with this is that it can be minimal and hard to detect until it's too late. 

Spills And Leaks

The most apparent causes of moisture are leaks and spills. If you have any pipe break or just a minor leak that may have found its way onto your hardwood, then you should keep an eye out. You should also be diligent when it comes to spills. Any liquid that is spilled has the potential to find a way into your hardwood and cause cupping.

One last source to think about is moisture brought in from the outside. When it's rainy or snowy, watch out for any of that being tracked onto your hardwood floors. 


This is the most invisible cause of moisture that can cause your hardwood floors to cup. Unfortunately, humidity can play a huge role in the maintenance of real wood floors. If the humidity increases in your home, then the hardwood will absorb the moisture to try and match the amount of it in the air. If it's humid enough, they will start to cup. This can even happen with different seasons as humidity levels change in your home.

How Can The Flooring Installation Process Cause Cupping?

This cause is also because of moisture but in a different way. If the subflooring that the hardwood gets installed on top of is damp at all, then cupping can happen. Another way that installation can affect cupping is if the boards used aren't acclimated to the humidity levels in that space yet. If they aren't, then they can eventually cup while trying to adapt to the humidity in your home.

1. Locate The Source Of The Moisture And Fix It

Finding and eliminating the source of the moisture that's causing the cupping is the most critical step. It can also be the easiest fix depending on the situation. Regardless of how you fix the cupping, if the moisture problem is still there, it's just going to happen again. If the cupping is just starting and you can fix the moisture issue, then the boards should return to normal on their own.

Will A Dehumidifier Help With Floor Cupping?

Dehumidifiers can help to fix cupping in a couple of different situations. If high humidity levels cause the cupping, then the dehumidifier will help to return those levels to normal. It can also help to take the moisture out of boards that are cupping for a reason other than humidity. Having a central dehumidifier will go even farther to help control your entire home's humidity and help with cupping.

Click here to start shopping for dehumidifiers on Amazon.

2. Consider Sanding The Cupped Boards

Using sanding to fix cupped hardwood floors should be considered with great caution. If it is done in an improper situation, then it can cause more harm than good. After you find and fix the source of the moisture that's causing the cupping, you need to wait before sanding.

Use a dehumidifier or just wait for the boards to try and return to normal. After several weeks and making sure that the moisture levels have returned to normal, you can think about sanding the cupping down and refinishing the boards.

If you sand cupped boards before waiting for them to fix themselves, then they could crown. Crowning is the opposite of cupping, where the middles are higher than the edges. This can happen if cupped boards are sanded, and then they shrink naturally. 

Different types of boards and finishes may also need other considerations before sanding. This method can have some significant repercussions, so you may want to consider hiring an expert to consult about it.

3. Call A Professional And Consider Replacing The Boards

If you are unsure about tackling this fix yourself or have already tried, and the issue persists, you may want to hire a professional. Hardwood floors are an important and often expensive part of your home. For that reason, this issue might be better in the hands of an expert.

After trying the other steps and consulting with someone, it may come down to replacing the cupped boards. If they are cupped beyond repair and sanding isn't an option, then all you can do is replace them. Here is a great visual guide to summarize wood floor cupping:

Will Cupped Hardwood Floors From Moisture Flatten?

Hardwood floors can flatten back out on their own, depending on the situation. The most important factor is removing the excess moisture. If you can do that and the boards are not extremely cupped, they have a good chance of flattening back out.

Cupping happens because the wood expands from moisture. This means that when that excess moisture is gone, the board will constrict back to its normal shape as it realigns with the climate in your home. 

How Do You Stop Hardwood Floors From Cupping?

The best way to prevent cupping is the prevent excess moisture! Make sure that you are taking proper care with your hardwood flooring by not wet mopping it and cleaning up spills as soon as they happen. You should also make sure that when the flooring is installed, the boards that are used are acclimated to your area's humidity.

Monitoring and controlling your home's humidity levels also helps to prevent cupping. Having some type of climate control is the best way to monitor and fix humidity issues. Using a special meter is also a great way to check the moisture levels inside the hardwood flooring!

Start shopping for wood moisture meters here on Amazon!

Is Hardwood Floor Cupping Normal?

Moist, swollen and receding parquet after water leakage

Cupping is a very normal reaction of the wood to excess moisture. Cupping is so normal that it is not uncommon to happen every year in the warmer months. Then it generally returns to normal as the air starts to dry out again.

Final Thoughts

Cupping is a very common issue that happens when there is excess moisture coming in contact with hardwood floors. The moisture can come from several different places. One of the most common causes is rises in humidity. If the moisture problem is fully resolved and the cupping is minimal, then the flooring will go back to its normal shape. Cupping is one possibility to think about when considering adding beautiful hardwood floors to your home!

To learn more about hardwood floors, click on the links below:

Why Does My New Hardwood Floor Squeak? [With Tips On What To Do About It!]

Does A Hardwood Floor Need Underlayment Or Subfloor?

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