Wood inside the house 

Wood is the most valuable building material for the house.
A cube of only 1.0m³ has an interior surface of 200m² .This capillary porous body with its large inner surface is in permanent exchange of humidity with its environment.       
The wood absorbs the humidity surrounding it or gives it off until an 
equilibrium is reached. Water either liquid or in form of steam is stored in the wood. The hollow spaces of the cells contain the liquid more volatile water, 
called free water, whereas steam is bound in the smaller hollow spaces of the cell walls, the fibres and is called bound water. Fibre saturation with bound water is obtained at a humidity content of approx. 30%. The wood is then in hygroscopic ba lance with an approx. 100% relative air humidity. The balance  humidity of the wood depends on th degree of humidity and temperature around it. It warps because its volume changes permanently while absorbing or giving off humidity particularly when this is between 6 and 30% It depends 
very much on how the wood is treated to maintain this outstanding quality. 
Because of its large surface all interior wood needs a protection against soiling where wood humidity does not exceed 18% .For this purpose the oils and waxes mentioned further down are applied. Sealing wood surfaces with synthetical resin varnishes means destroying the unique quality of wood.       
A sealed wood or cork floor could as well be replaced by a synthetical one.