Humidity affects hardwood floors in many ways, but you can prevent damage
Humidity causes a number of issues for hardwood floors.
Damage such as buckling, cupping, crowning, cracking, splitting, and gapping can be permanent.
Relative humidity should be between 30% and 50% for most types of hardwood flooring.
Protect your floors with humidity prevention and preparation efforts.
You can always tell when the humidity in the air is not in its normal range. You are either uncomfortable because the air is so thick, you can almost touch it, or you are 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 below what humidity is, how it affects your floors, and what you can do to protect them.
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.
The more saturated the air is with moisture, or the higher the relative humidity, the stickier the air feels. Conversely, the lower the moisture content of the air, the lower the relative humidity and the drier the air feels. Relative humidity also impacts how fast moisture will evaporate, as air with higher humidity will not absorb more water as readily as air with lower humidity, and humid air can distribute moisture into furnishings and other materials.
According to the United States Environmental Protection Agency, indoor air is most comfortable when humidity levels fall between 30% and 50%. Coincidentally, that is also the range where hardwood floors are safest. Since wood is a naturally porous material that absorbs water—including moisture from the air—humid indoor air affects hardwood floors and can damage them, regardless of hardwood plank sizes.
Even though the wood in your flooring is no longer living, it reacts to humidity just like living trees do. As they take in moisture, the wood fibers expand, swelling and pressing against each other. If individual fibers expand far enough, they eventually stretch the size and shape of the wood itself, causing boards to swell, shift, and twist. Then, when humidity levels in the air go down, the moisture leaves the wood, but the wood can remain misshapen.
Let flooring like hardwood and laminate acclimate to your home's humidity before installation to ensure it won’t warp or shift. Your flooring pro can guide you on how long to let it adapt.
But too much humidity is not the only danger your wood flooring faces, so it is important to learn how to care for hardwood floors. In climates where the air is dry, wood products, including hardwood floors, can lose too much moisture. This makes the fibers and boards themselves shrink, causing them to be susceptible to cracking, splitting, or gapping that can become permanent over time.
To avoid doing permanent damage to your wood flooring and negating the investment you have made in your hardwood flooring installation cost, it is important to maintain a moderate humidity in your home, ideally between 30% and 50%—although some exotic wood species do best with even higher humidity levels, from 50% to 70%. To do this, you may need to use a humidifier or dehumidifier, depending on local weather, the season, and your home heating method.
Warm air holds more water than cool air, so higher humidity is more likely to occur when the temperature rises outside. As the temperature drops, it holds less water, so the relative humidity goes down. However, artificial heating in homes can cause the opposite effect—in winter, when relative humidity is low outside due to low temperatures, furnaces, fireplaces, and forced air systems all remove natural humidity from the air and dry it out even further.
What does this mean for your home and your wood flooring? You will want to monitor carefully both the temperature and humidity inside your home so that you learn how the two measurements impact each other. Just like with indoor humidity levels, keeping an even indoor temperature will prevent swings that can make your flooring swell and shrink.
Simply put, you do not want hardwood flooring to get too hot or too cold; keeping the air around it at a relatively consistent temperature will help balance the humidity levels and stabilize the floor.
You should keep most wood flooring at a temperature between 65 and 75 degrees Fahrenheit (18 and 24 degrees Celsius), but your floor’s needs may vary. While domestic woods like oak and walnut may be able to handle slightly larger temperature swings, exotic species like Brazilian cherry and acacia can be more sensitive to seasonal changes. Be sure you know what type of wood your flooring is made of and what the manufacturer recommends.
Experts advise setting the thermostat to an even temperature in the middle of your floor’s preferred range that is still comfortable to you. While that may vary slightly, depending on the season and time of day, ideally it should not fluctuate more than a few degrees over the course of 24 hours. Even at night or when you are gone on vacation, it is important to keep your home’s temperature relatively even across hours and days to prevent your flooring from having to acclimate to temperature swings.
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.”
If you notice any of these signs, take action right away to stop the problem from getting worse. If you catch it early enough, there is a chance your flooring will return to normal or you can repair lingering problems. But if the damage is moderate to severe, or you have specific questions, contact a local hardwood floor installer for professional advice as soon as you can.
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 is not common for this to happen, it is possible with the right conditions.
Cupping happens when extreme humidity comes from areas below the floor, like a basement or crawl space, causing the edges of the planks to push up higher than the center. The result is a cup shape where the middle is lower than the edges.
To fix this issue, first you will need to identify the problem. Your interior relative humidity levels could be substantially higher above the floorboard. On the other hand, the humidity could be seeping from your basement or crawl space into your subfloors. It is also possible that you have a water leak.
“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 have identified the issue, you can use a dehumidifier or fan to dry your floors out and return them to their natural state. After you have reversed the cupping effect, consider sanding and refinishing your floor.
While the cupping effect causes the edges of hardwood flooring to rise higher than in the middle, crowning is the opposite—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, or if your floor was previously cupping and the edges were sanded before it was thoroughly dry.
It is 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. The best way to prevent floorboards from cracking is by ensuring that there are not 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.
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 and dirt to enter the flooring.
When the humidity levels are low during dry months, your hardwood floors could shrink excessively, leaving a gap between each board. Then, when it heats up again and there is more humidity in the air, the gaps will fill themselves in.
The best approach to protect your home is prevention and preparation. While you cannot prevent extreme fluctuations outdoors, you can purchase a humidifier and dehumidifier for use in different seasons to help control your humidity levels indoors. Besides that, other ways you can protect your floors include the following:
Know the manufacturer’s recommendations: While most types of hardwood specify humidity levels between 30% and 50% and temperatures between 60 and 80 degrees Fahrenheit (16 and 27 degrees Celsius), some manufacturers recommend humidity levels between 40% and 60%. For certain exotic woods, it can even be as high as 50 to 70% humidity, with temperatures between 65 and 75 degrees Fahrenheit (18 and 24 degrees Celsius).
Clean your hardwood floors thoroughly: Use cleaning products designed for hardwood floors and do not allow water to sit on them.
Monitor your home’s humidity: Buy a hygrometer for your home and pay attention to the humidity levels. If they rise or fall outside of your floor’s recommended levels, use your humidifier or dehumidifier to bring it back into optimal range. While this might seem like a hassle or extra expense, consider it an investment against the cost to refinish hardwood floors.
Set your home’s temperature controls: Use a programmable thermostat to keep your home’s temperature even around the clock and throughout the year. While you may want it a bit warmer in winter and cooler during the summer, try to prevent dramatic temperature swings. This can be good for your floors and your electrical bills.
Make sure floors are properly sealed, finished, and installed: This will help them resist soaking up humidity from the air or losing moisture when the air is too dry.
Leave space: Each board needs room for natural expansion.
Open your windows: When outside temperature and humidity levels are comfortable and within the recommended ranges for your flooring, open windows to help balance humidity levels and temperature naturally without using extra electricity.
