Does lumber expand across the grain or along the grain?

Expansion in length is much less than expansion across the grain (so small that it doesn't matter) and expansion even across the grain varies depending on whether the wood is plain-sawn or quarter sawn. read more

Wood moves much more across the grain, tangent to the growth rings. Green lumber shrinks as much as 8 percent in this direction. But it shrinks only half as much (4 percent) in the radial direction, extending out from the pith along the radius of the growth rings. read more

Grain direction determines a board's strength . If you've tried, you know that wood is far easier to split along the grain than it is to break across the grain. This is because wood is made up of tough cellulose fibers that are about 100 times longer than they are wide. read more