I'm confused about the way solid wood floors are traditionally
installed, given my understanding of the wood and water vapor.
First, I understand that wood floors are typically nailed to a plywood
substrate. It seems that fixing the wood in place would not allow any
room for the planks to expand or contract across their width,
presenting the possibility of cracks in dry weather or buckling in
damp weather. Why isn't this an issue?
Also, laminate floors are typically installed as a floating floor,
with an expansion gap around the periphery. Is this difference in
technique because laminate floors are less stable with respect to
humidity and temperature than solid wood floors?
Second, I believe that wood floors are only finished on their top
surface. It seems that this would create a big difference in the
permeability of the top and bottom surfaces, and that the uneven water
vapor transfer could cause the planks to cup. Why isn't this an
issue? It seems like it would be easy to finish the underside before
installation, but I've never heard of this being done.
Thanks for your comments.