Fluctuations in relative humidity can affect your wooden flooring. Wood’s moisture content is directly affected by the amount of moisture in the air. It absorbs moisture when levels are high and gives it off when they’re low. As a rough guide, a 10% change can cause up to half an inch expansion or contraction in boards. So, it’s vital to keep humidity at a constant level.
In the UK, we have a changeable climate; average outside humidity ranges between 25-75% throughout the year. In the home it is usually between 35-55%. While it doesn’t vary as much, it’s still necessary to take steps to prevent any damage to your floors.
Outside, levels are at their highest in winter and lowest in the summer months. However, in the home, conditions are different and the opposite occurs. In summer, humidity inside peaks causing wood to expand. In winter, the air is drier so it contracts. Why? Because air from outside is warmed or cooled quickly when it comes into the house without any change in hydration, hence humidity levels rise or fall rapidly.
For example, in winter outside air is drawn in and heated from say 2 to 20 degrees Celsius without any moisture added, relative humidity level subsequently falls. A room that’s kept at a constant 21 degrees all year could have a 50% relative humidity in summer which may drop to around 30% in the winter months. If you have under floor heating, the effects will be more severe.
It is recommended you purchase a humidity meter for your home to monitor variations. In some cases, it may be necessary to use a humidifier or de-humidifier at certain times of the year.