Oak cupping and warping

When during drying does oak lumber stop cupping and warping? July 4, 2000

Q.
I have a sawmill and a solar kiln, and cut mostly red and white oak. The lumber is end-coated, and stickered in piles 8 feet high and kept inside a building for up to a year before being put in the solar kiln. I have started using 4-foot x 9-foot x 7-inch slabs of cement (3000lb) on the top of my piles to help stop the cupping and bowing.

My question: At what moisture content (MC) does the cupping and bowing cease? If I put the wood in the solar kiln at 12 to 20 percent, is the weight still needed?

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Most of the movement in the wood will happen before it gets down to around 19 percent. However, the weight is still a good idea during kiln drying.

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I agree with the last respondent. Note too that a lot of cup can still occur at the lower MCs if the wood is over-dried, and weight will not help control it.
Gene Wengert, forum moderator