stretch wrote:
The rest of the house and the subfloor should shrink and expand at
the
same rate as the wood floor. That is why you acclimate the wood
flooring before you install it. If everything expands and contracts
at
the same rate, you should not have any problems.

Everything expands and contracts at different rates, both based on
temperature and on humidity. The same species of wood can have
markedly different coefficients of expansion depending on whether the
wood was flat or quarter sawn.

http://tinyurl.com/4vbgy

The plywood subfloor and finish flooring will not react to the changes
in humidity in the same way at all. That's one of the major benefits
of plywood - the cross grain limits the expansion and contraction.

R