6 Ways Humidity Affects Hardwood Floors

Bry'Ana Arvie
Written by Bry'Ana Arvie
Reviewed by Robert Tschudi
Updated April 12, 2022
Stylish dining room interior with hardwood flooring
Photo: FollowTheFlow / iStock / Getty Images Plus

Highlights

  • Humidity causes a number of issues for your hardwood floors

  • Relative humidity in your home should be between 30%–50%

  • Protect your floors with humidity prevention and preparation efforts

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You can always tell when the humidity in the air isn’t in its normal range. You’re either uncomfortable because the air’s so thick you can touch it, or you’re reaching for the nearest bottle of lotion because the air is so dry your skin is starting to itch. While you know how humidity affects the human body, do you know how it affects your hardwood floors? Find out what humidity is, how humidity affects your floors, and how to protect them below.

What Is Relative Humidity?

Before discussing how humidity impacts hardwood floors, let’s start with a clear definition of relative humidity. Relative humidity (RH) is the water vapor in the air relative to how much water vapor the air can hold at its temperature, expressed as a percentage. For example, RH at 50% means the air is at half of its water vapor capacity that it can hold.    

So, the relative humidity levels that your hardwood floors should be exposed to while still allowing them to stay in good shape is 30% to 50%. Anywhere outside of that best-case scenario is when problems arise. 

6 Ways Humidity Affects Hardwood Floors

Let’s cover what happens to hardwood floors if humidity levels are way above the optimal RH range or drop too low. 

“Humidity is the enemy of hardwood flooring,” says Bob Tschudi, Angi Expert and Raleigh, NC-based general contractor. “Once you see signs of cupping or buckling, you have to take immediate action to not only stop it, but remove the humidity to restore the flooring back to normal.”

1. Buckling

When your hardwood floors are faced with extreme humidity, the excessive moisture causes them to expand and pull away from the subfloor, potentially up to a few inches. While it’s not common for this to happen, it’s possible with the right conditions. 

2. Cupping

Cupping happens when extreme humidity comes from areas below your floor like a basement or crawlspace, causing the edge of your planks to push up higher than the center. The result is a cup shape where the middle is lower than the edges—similar to a cup. To fix this issue, first, you’ll need to identify the problem. Your interior relative humidity levels could be substantially high above the floorboard. On the other hand, the humidity could be seeping from your basement or crawlspace into your subfloors. It’s also possible that you could be facing a water leak, causing your problem. 

“On one of our remodeling projects, the plumber incorrectly installed a water supply line and, overnight, the hardwoods were covered in water. All the flooring started cupping,” says Tschudi. “We immediately contracted a moisture remediation contractor who had equipment to remove moisture from the flooring and reverse the cupping. But it was a good lesson in how water can destroy flooring.”

Once you’ve identified the issue, you can use a dehumidifier or fan to dry your floors out and return them to their natural state. After you’ve reversed the cupping effect, consider sanding and refinishing your floor.

3. Crowning

While the cupping effect causes the edges of hardwood flooring to rise higher than the middle, crowning is the opposite. Crowning is when the middle of the board is higher than its edges. This effect happens because of a moisture imbalance caused over time. One reason your hardwood floors might be crowning is if water sat on the floorboards for too long. Another reason is if your floor was previously cupping and the edges were sanded before it was thoroughly dry. 

4. Cracking

Woman changing water container in dehumidifier
Photo: Daria Kulkova / iStock / Getty Images Plus

It’s normal for wood floors to experience some level of contraction and expansion. But during extreme humidity, your hardwood floors can expand tremendously and push into the neighboring boards—causing them to crack. And the best way to prevent your floorboards from cracking is by ensuring that there aren’t any drastic humidity changes within your home by keeping a balance throughout. To do this, you can use a humidifier in the dry months and a dehumidifier when the season changes and there’s more humidity in the air.

5. Splitting 

If your home suffers from extremely dry or humid conditions, it can lead to splits or splinters in your wood against the grain. This splitting effect is permanent, unlike other damages to your hardwood floor caused by humidity, because the breakage affects the wood's integrity and seeps into the finish, allowing water, dirt, and more to enter the flooring. 

6. Gapping

When the humidity levels are pretty low during dry months, your hardwood floors could shrink excessively, leaving a gap between each board. Then when it heats up again, and there’s more humidity in the air, the gaps will fill themselves in.

How Do I Protect My Floors From Humidity?

The best method to protect your home is prevention and preparation. While you can’t prevent extreme humidity fluctuations, you can purchase a humidifier and dehumidifier for dry and humid seasons to help control your humidity levels. Besides that, a few other ways you can protect your floors is by:

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