Oak cupping and warping

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

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?

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.

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

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