Climate
Humidity and stability: how Canadian seasons move a wood floor
Wood is a humidity sponge. It releases moisture when the surrounding air is dry and takes it back up when the air is damp, and as it does, it changes size. In much of Canada the indoor air swings a long way between a heated winter and a humid summer, which is why moisture — not foot traffic — is the factor that most often shapes how a wood floor performs.
The winter heating problem
When outdoor air is cold, it holds little moisture. Heating that air indoors lowers its relative humidity further, and a home running forced-air heat through a Canadian January can sit well below the comfortable range for wood. As the air dries, solid boards give up moisture and shrink across their width. Thin gaps can open between boards. When summer humidity returns, the boards take moisture back and the gaps close again.
This seasonal opening and closing is normal behaviour for solid wood, not a defect. It is more visible with wide boards and with species that move more, and less visible with narrow boards and with engineered construction.
A target worth holding
Health Canada suggests keeping indoor relative humidity within a moderate range and avoiding extended periods at the dry or damp ends. A stable indoor environment is also what most wood-floor guidance asks for. See the reference linked at the end of this article.
Why engineered floors move less
The cross-laminated core of an engineered board is built to fight movement. Because the inner plies have their grain running in alternating directions, they restrain one another, and the whole board stays closer to its original dimensions through a humidity swing. That is the practical reason engineered planks are so often recommended over concrete slabs and in basements, where moisture conditions are harder to control.
Acclimation before installation
One of the most overlooked steps is letting the flooring adjust to the room before it goes down. If boards are installed straight from a cold delivery truck into a heated home, they will keep changing size after installation. The usual practice is to bring the material into the space, in its normal operating conditions, and let it reach equilibrium before fastening anything.
What to confirm before install day
- The home is at its normal lived-in temperature and humidity, not a construction-phase extreme.
- The subfloor moisture has been checked, especially over concrete.
- The flooring has spent enough time in the room to settle.
- The plan accounts for expansion space at the walls.
Living with seasonal movement
Some movement is simply part of owning a wood floor, and chasing a perfectly gap-free surface year-round is unrealistic in a four-season climate. The more useful goal is to avoid extremes: a humidifier in the dry months and good ventilation in the humid ones keep the swings smaller, which keeps the floor calmer.