Did you ever wonder how wood absorbs moisture?Wood Flooring and Moisture
Plants draw moisture up the stem to the leaves. Wood from a tree is just a slice of the stem.
Wood cells can be as long as 2 1/2″ and they look like tubes. When the wood is alive they are full of moisture
Oak has rather wide cells and that give it a distinct grain. Mahogany is a similar shape of cell.
Sealing the end grains can prevent any wood from expanding and contracting quite so much and so quickly.
Many exterior builders seal the lumber all 6 sides.
The more wood flooring is dried, the harder it gets. When wood flooring is dried using heat the sap cooks. This cooked sap will not absorb moisture the same as air dried or partially dried floors, and it will actually deter the infiltration of moisture some species like pine.
This is why Merv dries his flooring to 6% rather than 8% moisture content.
Quite often floors are destroyed by moisture damage– It takes considerably more moisture to make 6% flooring swell than it does flooring dried less.