Track 2
Moisture & Movement
How wood behaves as a material. The most important track for avoiding mistakes — covers why boards warp, cup, twist, and shrink.
10 published guides in this track
Moisture Content Explained
Moisture content (MC) is the percentage measure of water in wood, and it’s the starting point for predicting movement, acclimation, and drying decisions.
Equilibrium Moisture Content
Equilibrium moisture content (EMC) is the moisture level wood naturally settles at for a given temperature and relative humidity, and it’s the key to seasonal movement and acclimatisation.
Why Wood Moves
Wood movement is the predictable swelling and shrinkage of wood as moisture content changes, and understanding direction (tangential/radial/longitudinal) lets you design joints and panels that survive seasons.
Tangential vs Radial Movement
Tangential vs radial is the single most useful cut-angle concept in timber: it tells you how much a board will move across its width for the same moisture change.
Longitudinal Movement (and Why It's Small)
Longitudinal movement is the small (usually negligible) change in wood’s length with moisture, and understanding the exceptions (juvenile and reaction wood) prevents “mystery” bowing and twist.
Shrinkage and Swelling
In the previous guides, we covered the three axes of wood movement — tangential, radial, and longitudinal — and the reasons behind each. Now it's time to bring them together.
How Humidity Affects Wood
Humidity (relative humidity, RH) is the real control dial for wood: it sets EMC, which drives moisture content change and therefore movement.
Case Hardening and Drying Stress
Case hardening is locked-in drying stress from moisture gradients (shell vs core), and it’s why “dry” timber can still spring, bow, and fight you when you machine it.
Internal Stresses in Timber
Internal stress is why boards move after you cut them—sometimes from drying (case hardening), sometimes from growth stresses locked in while the tree was alive.
Dimensional Stability
Dimensional stability is how much a timber changes size for a given moisture swing, and you can improve it with species choice, cut angle, construction, and realistic allowances.