The relative humidity is the quantity of water proportionately present in the air. You need a hygrometer to measure the humidity. Most weather stations have a hygrometer. Too high humidity can cause mould, vermin… This can also have an influence on wooden floors.
The right relative humidity is between 40% & 55%. So it is certainly important to install the wooden floor when the humidity is between these values, and it is also important to keep an eye on this percentage after installation. A different percentage could cause the wooden floor to shrink or expand.
If the relative humidity is too low, the wood will repel moisture and shrink. This can result in irreparable cracks. If the air humidity is too high, the wood will absorb moisture so the planks will expand and lift.
Humidifiers with built-in hygrostat can be used to constantly measure the relative humidity in a space.
This appliance measures the humidity in the air and will humidify the space if required by means of cold water technology.
The relative humidity can vary strongly between summer and winter (variations between 90% - 20%), so the wooden floor will expand and shrink depending on the time of the year. The most difficult period for wood is the winter. In freezing temperatures there may be extremely low humidity (down to 20%). If the spaces are then heated more, the wooden floor expels the last moisture so the planks react and can become detached from the joints.
It is important to remember that wood is a natural product with the possibility of deformation, cracks or open gaps in the joints and this must be tolerated.
Regularly measure the relative humidity. It is often necessary to place an electric air humidifier to be able to maintain sufficient relative humidity (40 to 55%). When purchasing a humidifier take account of the size of the space (cubic metres). It is recommended to place the humidifier in the middle of the space, as far as possible away from the heat source (radiator, hearth).
Spaces not occupied in the winter must be heated to minimum of 10 °C.