Cracks in hardwood floors: Why do the wood floors crack in winter?

The new wood floor is down, but a few months later comes the first surprise: In the worst case, you can see joints or cracks.

What could have caused cracks in hardwood floors? Most of the time, it’s because of how warm or cold the room is. During the cold season, when the heat was on, the humidity in the rooms was too low, so the wood floors dried out.

As the moisture in the wood goes down, the wood gets smaller.

To reduce the chance of cracks and joints, it is best to carefully prepare the subfloor before putting down the wood floor and glue it firmly to the whole surface.

Wood is hygroscopic, which means it retains water. It alters the amount of water in the wood and the size of the wood floor to adapt to the climate of the space.

You must have an ideal moisture level in wood flooring. When the wood floor is delivered and installed, the moisture level is 9 + 2%. This wood has the same moisture content as a room that is 60-71°F and 55-60% humid.

This normal climate should be reached on average throughout the year, but heating the rooms always makes it too hot in the summer and too cold in the winter.

So, a natural product like wood will always change. The wood floor will grow a bit in the summer because of the room temperature, and it will shrink slightly in the winter. This makes wood different from other (artificial) materials or floor coverings.

Wood floor is very sensitive to the climate inside, so a change in the relative humidity of the room air affects this wood floor covering.

Whether a room is heated with underfloor or convector heating, the relative humidity is often only 34% or less. This means that only 6.8% of the wood is wet. When this happens, there are always holes in the wood.

This is also true of sealed wood floors because sealing layers can’t stop moisture from moving between the wood and the air in the room; they can only slow it down a little.

Because wood swells and shrinks because of how it is made, small holes appear in the sealing film. Also, sealing a wood floor does not make it waterproof. Instead, it protects the surface and makes it easier to clean.

Even when the heat is on, adding more moisture to the air in the room can make the small gaps that appear when the heat is off going away or keep them from happening. This process doesn’t hurt parquet or other wood floors in any way.

For this, you should use a humidifier with a built-in humidity controller. The best ones are evaporators.

Constant humidity is good for the residents’ health and the hardwood floors’ condition, which should also be seen in this way.

Due to their small size, more than the containers that come with radiator heating systems are needed to keep the humidity level in the room constant and within the rules.

They only hold a quarter to half a liter of water, while the air in a room with a floor area of 172 Sq. ft and a normal height need about liters of water in 24 hours to reach a humidity level of 45 to 50%.

Controlling and maintaining a relative humidity of 55% is recommended because it has the following advantages:

  • Preventing the wood from drying out to the point where it’s no longer acceptable
  • Minimizing the formation of gaps – Reducing shrinkage stresses in the adhesive layer, both for new and old subfloors
  • Improving the air’s cleanliness.

Because of how the room’s climate, wood’s moisture content, and heating systems work together, wooden floors will always have gaps.

During the season, joints with widths between 0.3 and 0.8 millimeters are perfectly normal.

But joints with a width of 1 mm or more are no longer acceptable. But these gaps only happen if the humidity in the rooms in question isn’t watched and controlled.

How do I prevent cracks and joints?

How should I take care of the hardwood floor during heating so that it doesn’t get cracks or wide gaps?

When the floor is heated, there are often big holes in the wood. When wood floors are delivered and put down, the wood has about 9% moisture.

This wood’s moisture level is the same as a room temperature of 60 to 71 degrees and relative humidity of 55 to 60 percent.

During the winter, the humidity often drops to 34% or even lower when the house is heated.

Because wood is a natural material that changes when the temperature or humidity changes, this has an effect. The wood gives off moisture (there is only 6.8 percent moisture in wood) and shrinks as a result. This can lead to spaces.

This is also true of sealed wood floors because sealing layers can’t stop moisture from moving between the wood and the air in the room; they can only slow it down.

The right winter care for the wooden floor

Before winter, you should clean and take care of the floor with soap. Soap for wooden floors gets the dirt out of the pores.

It cleans the wood and re-oils it because it has a lot of fat. This keeps the fibers of the wood soft and pliable.

When wood fibers are pushed down, they can spring back up again. This means that small dents and scratches can almost be wiped away. After a short time, the excess water and dirt are wiped with the wiper and washed away with clear water.

The floor can look dry during heating because there isn’t enough humidity in the air. You should wipe it with a larger amount of soap, but it shouldn’t be too wet. This makes the wood smooth again.

It’s important not to wipe with too much water because stress cracks can happen when much water comes at once.

Wooden floor plus underfloor heating

When caring for a natural wood floor in the winter with underfloor heating, you should also note that the temperature should be lowered before wiping or re-oiling to keep the floor from drying out or even cracking.

The surface temperature of the floor heating should be at most 84 degrees, too. It would be best if it stayed within 78 degrees.

Increasing humidity is important for wood floors.

But taking care of joints won’t be enough to stop them. To keep your wood floors looking nice, you should keep the humidity between 40 and 60 percent, even when it’s cold outside. Also, the best room temperature is between 64 and 68 degrees.

Then, not only does your wooden floor feel good, but the right amount of humidity is also good for your lungs and helps keep colds and infections at bay.

For instance, humidifiers, plants, and indoor fountains are good ways to add moisture to the air.

During the heating period, we also suggest that shock ventilation be done. The already low humidity drops, even more when you let your floor air out for a long time, which makes gaps appear in your floor.