Wood shrinkage
February 14, 2013 | 6:00 pm CST

Q: Somewhere in my woodworking background, it seems that I learned that wood shrinks or grows about 1/64 inch per 1 degree of moisture across the grain. Is this right?

A: There is quite a bit of variability in shrinkage for the different species. Teak shrinks or swells very little (1 percent size change for an 8 percent MC change) and oak shrinks or swells quite a bit (1 percent size change for less than 3 percent MC change). As a general rule of thumb, kiln-dried lumber shrinks or swells in width about 1 percent for a 4 percent MC change for flatsawn, or about 1 percent for a 7 percent MC change with quartersawn lumber. (Shrinkage or swelling in thickness is about 1 percent for a 7 percent MC change for flatsawn and 1 percent for 4 percent MC for quartersawn.)

Stated another way, a 1-inch-wide piece of kiln-dried flatsawn lumber will shrink or swell 0.0025 inch when the moisture changes by 1 percent MC. A 6-inch-wide piece would shrink or swell 0.015 inch with a 1 percent MC change, which is 1/64 inch. Perhaps this is the basis for your recollection.

Have something to say? Share your thoughts with us in the comments below.

Profile picture for user genewengert
About the author
Gene Wengert

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 45 years. He is extension specialist emeritus at the University of Wisconsin-Madison.