My friend said yesterday that houses that are built with birch don't need to be chemically treated.
The wood what is now 50 years old has dark dots on the surface, but it seems to be strong. The wood is exposed to a litte water, since it is used only for those parts under the roof.
I have thought before that the wood would rot inside during such long periods of time. There may however be some fungi on the material, since the dark dots are very evident on the surface of the wood. Is it dangerous to build houses without chemically treated wood?