Impact of humidity
Wood is a hygroscopic material which absorbs water vapour from the environment. It expands when humidity increases and shrinks when humidity decreases. This reaction is influenced by temperature in the room. Variable air humidity conditions cause the changes in dimensions and shape of boards which in turn may lead to formation of gaps and cracks when air humidity is too high or too low for a prolonged period of time. This relationship is shown in the table below:
|
Temperature in °C |
10 °C |
15°C |
20°C |
25°C |
30°C |
|
Ambient relative humidity |
Wood moisture content |
||||
|
20 % |
4,7 % |
4,7 % |
4,6 % |
4,4 % |
4,3 % |
|
30 % |
6,3 % |
6,2 % |
6,1 % |
6,0 % |
5,9 % |
|
40 % |
7,9 % |
7,8 % |
7,7 % |
7,6 % |
7,5 % |
|
50 % |
9,4 % |
9,3 % |
9,2 % |
9,0 % |
9,0 % |
|
60 % |
11,1 % |
11,0 % |
10,8 % |
10,6 % |
10,5 % |
|
70 % |
13,3 % |
13,2 % |
13,0 % |
12,8 % |
12,6 % |
|
80 % |
16,2 % |
16,3 % |
16,0 % |
15,8 % |
15,6 % |
|
90 % |
21,2 % |
20,8 % |
20,6 % |
20,3 % |
20,1 % |
Table. Wood moisture content depending on atmospheric conditions.
In order to minimize natural changes in wood properties, maintain air humidity of 45% - 60% and temperature of 18°C – 22°C in the room. Content of water trapped in wood (i.e. water which can not be removed by a prolonged drying) is 4-6%. In winter, when air humidity inside and outside the building is considerably reduced, it is recommended to humidify the room using electric humidifiers. In air conditioned rooms, air humidity may be very low. Slovpol Wood are dried to moisture content level of 10% +/- 3%. A lower moisture content can not be achieved technically because the wood dried to the moisture content level of 6% reaches the moisture content level of about 10% again when treated.
Humidity is the most important factor causing shrinkage, swelling and warping of wood. Wood swells when humidity increases and shrinks when humidity decreases. These processes occur with a significant intensity perpendicularly to wood fibres. These processes can be omitted when occurring along wood fibres. Laminated board has a base layer made of mutually perpendicular plywood. Thanks to this it is much less susceptible to swelling and shrinking than solid wood boards. However, large changes in wood moisture content may lead to cracks and delamination of wood (in case of laminated boards). It is important to ensure that the base remains dry. When cleaning the floor, use only a minimum quantity of water (a damp cloth should be used). Care should be taken to ensure that air humidity (relative humidity) does not vary too much. Relative humidity must be between 40 and 60%.