Hardwood floors — gorgeous, classic, and elegant; however, they do seem to have a weakness. 

Humidity.

Hardwood floors need just the right amount of humidity, not too high, not too low. You need to keep the humidity level in your house in a particular range for your hardwood floor to stay in the best shape through the test of time.

The recommended humidity level for hardwood floors is between 30%-50% within a temperature range of 60 to 80 degrees Fahrenheit. Higher or lower humidity can degrade the appearance and quality of the hardwood floor as wood is sensitive to moisture.

So, how does humidity affect hardwood floors? How can you ensure optimum humidity for hardwood floors? Let’s discuss.

What are Humidity and Relative Humidity?

Humidity is the total volume of water vapor present in the air. The relative humidity is the amount of moisture present, expressed as a percentage of the maximum water vapor the air can hold while maintaining the same temperature. The amount of moisture necessary to saturate the air increases with temperature. This is why the air holds more water or moisture when it is warmer. 

How Does Humidity Affect Hardwood Floors?

To understand the effect of humidity on hardwood floors, first, we need to focus on the wood itself. Wood is a hygroscopic material. Meaning wood has a tendency to absorb moisture from the air. On the contrary, wood will give off/release water and contract or shrink in size in low humid conditions. 

The hardwood floors contract or expand when moisture fluctuation is left unaddressed—the shrinking and expansion cause the hardwood floors to create spacing or push against each other. The impact is worse in areas where humidity varies greatly with seasonal changes as it can cause the hardwood planks to move. 

The effect of different humidity for hardwood floors are –

Humidity Levels	Comment	Impact on hardwood floors
0%-25%	Critically low	Causes moisture to evaporate from hardwood — causing it to shrink and the seams to open wider. Leads to cracking, gapping between planks, and splintering.
25%-35%	Low	Long-time exposure causes the wood to contract and expand with seasonal changes. However, the movement should be minimal.
35%-50%	Ideal	This is the ideal humidity level for any hardwood floor that will not expand or contract the wood.
50%-60%	High	Long-time exposure causes the wood to contract and expand as the season changes.
60%-100%	Critically high	Causes the planks to swell and push against one another and ultimately deform the structure.

Is Low Humidity Bad for Hardwood Floors?

As wood is a hygroscopic material, humidity can impact the hardwood floor. The humidity level can drop due to natural and artificial reasons. In some areas, the moisture content of the air lowers seasonally. Additionally, people may keep their doors and windows closed during winter and turn up the heating system to dry up the indoor air. Using an air conditioner has a similar effect on the indoor moisture level.

Low humidity level (lower than 35%) can have the following effect on hardwood floors –

It can leave gaps in hardwood floors

As the humidity level drops, the hardwood floor loses moisture and contracts. It causes the gap between floors to broaden. It can also lead to uneven spacings between planks.

It can cause hardwood floor to split

As the hardwood floor loses moisture and dries out, it can become brittle and develop cracks along the grain of the wood. It can eventually cause splinters to stick out, which is a safety hazard you don’t want in your home.

It can damage hardwood finish

Low moisture in wood can make your hardwood floors look old and damaged. It makes them harder to manage and might need more frequent maintenance. 

Is High Humidity Bad for Hardwood Floors?

High humidity level also affects your hardwood floor as it can absorb excess moisture from the air and expand. Moisture content can directly impact wood’s physical dimensions. People living in high humid areas can often notice degradation in the appearance of their hardwood floors. Cleaning hardwood floors using water or spilling water frequently on the surface can also have the same effect. 

High humidity (higher than 55%) can have the following effect on your hardwood floors –

It can crack hardwood floors

Like low humidity, the high humidity level can also crack hardwood floors. When your hardwood floor absorbs moisture from the air, it results in swelling. With this expansion, pressure can mount between the boards and eventually causes them to press against one another. In extreme cases, boards can lose their structural integrity and crack.

It can create buckling in hardwood floors

Excessive moisture in the indoor air can cause the hardwood floor to warp or buckle. One common type of warping is cupping, which occurs when the edges of the wood plank rise and become higher than the center due to swelling. It often results from excessive relative humidity in the basement or crawl space.

It can cause hardwood floors to crown

When hardwood is left wet or moist for too long or sanded immediately after cupping occurs, it can result in crowning. Crowning is precisely the opposite of cupping, where the middle part of the wood planks is higher than the edge. When you sand the hardwood soon after cupping occurs, the raised edges of the board are sanded off. Afterward, when it dries out and returns to normal, those edges become lower than the rest. This is why you should give your board some time to return to its normal condition when any moisture-caused damage occurs. 

It weakens the wood

Wood gets stronger when it is dried. Wood with a 12-15% moisture content has about twice the bending and compression strength of freshly cut wood. Dried wood’s tensile strength peaks when the moisture content is 6-12%. Exposing it to moisture subsides hardwood’s tensile strength, affecting its longevity. 

What is the Best Humidity Level for Hardwood Floors?

The recommended humidity level for hardwood floors, which is the same as the recommended humidity level for your health, is between 38 percent and 42 percent. However, the humidity level between 35%-50% is also considered exemplary. You can use a humidistat or a hydrometer to measure the humidity level in your home. It is crucial to observe and maintain a healthy humidity level to maintain your physical and hardwood floor’s health.

You can tell if your home humidity level is too high or low even without a humidistat or a hydrometer. Here are a few tell-tale indications of high and low indoor moisture levels –

Signs of low humidity

• Dry and itchy skin
• Increased static electricity
• More respiratory illnesses or colds than usual
• Frequent bloody noses
• The increasing size of gaps between hardwood floorboards or in other wood furniture joints

Signs of high humidity

• The indoor air feels clammy and moist
• Foggy windows
• Musty smell around the house
• Presence of mold
• Worsened allergies

How to Keep Humidity Level Stable in Your Home 

To keep humidity levels stable in your home, you need to observe the indoor relative humidity year-round. If the humidity level goes above 42% or below 38%, you need to act accordingly. 

To stabilize your home’s humidity level, you need to use either a humidifier or a dehumidifier. A humidifier adds moisture to the air. Humidifiers are typically used during dry, winter weather. On the contrary, a dehumidifier removes moisture from the air — typically used in humid areas. Additionally, there is also a whole-home humidification system or central humidification, which does both. It uses a built-in humidity detector or hygrometer to check the humidity level, and it removes and adds moisture as needed.

Types of humidifiers

Warm mist humidifiers

The warm mist humidifier is the most common type of humidifier that heats water to convert it into vapor. The vaporized water is then released into the room to increase moisture level. It uses the most basic and oldest technology to add moisture. 

The main disadvantage of this technology is that it can get boiling hot and pose risks to your family members. Also, it is less energy efficient than other humidifiers. 

Cool mist humidifiers

Cool mist humidifiers use evaporative or ultrasonic technology to get the water out of the machine and into the air. It does not heat the water, which makes it relatively safer than warm mist humidifiers. The downside of this technology is, it can often create a puddle of water. It also uses wicks that you need to replace regularly. 

Types of dehumidifiers

Heat Pump Dehumidifier

These dehumidifiers use a fan, heat pump, and heat exchange coils to remove moisture from the air. A fan circulates the air through the extremely cold heat exchange coil, where the vapor condenses and then gets collected. Even though these are very effective and efficient, the main con is you will have to empty the water reservoir every couple of days.

Dehumidifying Ventilator

The dehumidifying ventilators work by using an exhaust fan to expel air outside. It uses a sensor and exhaust fan. These are typically used in basements, attics, and crawl spaces. It is not ideal to use this type of dehumidifier in other parts of the house as the exhaust fan can look odd and ruin the aesthetics.

Chemical Absorbent Dehumidifier

These dehumidifiers consist of hydrophilic materials, such as silica gel that absorbs moisture from the air. The residential units usually contain single-use desiccant-type cartridges, gel, and powder. These are also known as desiccant dehumidifiers. The downside of these humidifiers is they are less efficient, and some consider them to be wasteful as you need to replace the hydrophilic material quite often. 

It is crucial to maintain a healthy humidity level in your home — both for the sake of your health and your flooring. As for the humidity for hardwood, you want to avoid either extreme of the spectrum. It’s about finding the right balance and maintaining a consistent humidity level in your home. Your hardwood floor can now, too, remain in its perfect condition through the test of time by following the ways mentioned above.