Across the grain, not along it
Wood barely changes length along the grain and changes noticeably across it. A 300 mm (11.8 in) wide board can move a few millimeters between a damp summer and a heated winter. A tabletop screwed rigidly to a frame at both ends will split.
Acclimatize before machining
Bring timber into the space it will live in, sticker it so air reaches every face, and leave it. Then machine. A board flattened at 18% moisture and moved into a heated room at 8% will cup, and no amount of care at the planer prevents it.
Design for it
Slotted screw holes or buttons for tabletops. Floating panels in frames, never glued at the edges. Breadboard ends pinned in the middle and slotted at the sides.
The workshop test
If your machines rust overnight in autumn, your timber is absorbing the same moisture.
What comes up most often
How long should timber acclimatize?
Long enough to stop changing — typically one to two weeks indoors, stickered so air reaches all faces. Machining it the day it arrives is the most common cause of a project that moves afterwards.
Last reviewed 2026-08-12
