How To Protect Your Floor From Cold Weather

Many homeowners experience problems with wood floors during the winter. Cold weather tends to reduce the amount of moisture in the air, scientifically known as relative humidity. A low RH causes wood to dry out and shrink, resulting in gaps between the floor boards. A high RH in winter is less common, but it can cause mold to grow on wood flooring. The most important means of protecting your wood floor during winter are to select the proper materials for the floor and maintain the RH in your home within the desired range.


The materials used in wood flooring can generally be classified into solid wood and engineered wood. Engineered wood is also known by several other names, including composite wood, manufactured board and man-made wood. These terms refer to a range of products that consist of wood fiber, particles or veneer bound together with adhesives.

Some types of wood are more resistant to changes in size than others, a quantity known as the dimensional change coefficient. For example, red oak will shrink less than hickory as the RH decreases. Organizations such as U.S. Forest Service provide the DC coefficients for various types of wood.

Engineered wood is generally more stable than solid wood. However, the warranties for engineered wood often require these materials to be kept within a specific RH range such as 40 to 60 percent. It is often impractical to maintain this type of warranty by keeping a wood floor within a narrow RH range.

Homeowners can also minimize gaps in their floors during winter by selecting narrow boards. For example, boards that are 3 inches wide will shrink half as much as boards that are 6 inches wide over the same decrease in RH. The gaps in a floor with 3-inch boards will therefore be half as wide as the gaps in a floor with 6-inch boards.


One method of reducing the gaps in your floor during winter is to reduce the ventilation in your house. Cold air that enters your house from outside will eventually be heated, which reduces the RH of the air and causes floor gaps. For example, assume that the outside air has a temperature of 30 degrees Fahrenheit and an RH of 50 percent. The RH of this air will drop to 10 percent after it is warmed to 70 degrees Fahrenheit.

Ventilation is measured in terms of air changes per hour, which is the volume of air that enters the house in an hour divided by the interior volume of the house. Assume for this example that a house with 2,000 square feet has 8-foot ceilings, giving the house an interior volume of 2,000 x 8 = 16,000 cubic feet. Assume further that this house is ventilated at the rate of 16,000 cubic feet per hour. This house therefore has a ventilation rate of 1 ACH.

A modern house in good condition typically has a ventilation rate of 1 to 2 ACH, while leaky homes may have ventilation rates as high as 10 ACH. A home energy audit can measure the ventilation rate and identify sources of air leakage such as doors, windows and holes in the ceiling. These problems can often be solved by sealing the leakage sites.

Adding Moisture

Gaps in floorboards can often be reduced by adding moisture to the air, typically with the use of humidifiers. A typical home humidifier can add up to 6 pints of water to the air every hour. The American Society of Heating, Refrigerating and Air-Conditioning Engineers provides specific information on the relationship between adding moisture to the air and its effect on the air’s RH.