Wood shrinkage
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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.

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Gene Wengert

Gene Wengert (1942-2025) was popularly known as “The Wood Doctor.” He trained thousands of people in efficient use of wood for more than 50 years and authored foundational resources on wood technology. He worked at the University of Wisconsin-Madison and Virginia Tech. His popular "Wood Doctor's Rx" column has appeared regularly in FDM and FDMC magazine since 1978. Because so much of his advice was timeless, he asked that we continue to run his columns in memoriam.