Houtkrimp

Houtkrimp, literally “wood shrinkage” in Dutch, refers to the dimensional reduction of wood as it dries and loses moisture. It is an inherent property of wood caused by the hygroscopic nature of plant cells and the anisotropic structure of xylem. Wood shrinks differently along its axes: tangentially (along the growth rings) and radially (across the rings), with the tangential direction typically showing greater shrinkage. The third dimension, thickness, also decreases but follows the same directional pattern.

Most shrinkage occurs when moisture content falls from the fiber saturation point to oven-dry. Above the fiber saturation point, changes in moisture content cause relatively little dimensional change; below it, cell walls lose bound water and wood contracts. The exact magnitude of shrinkage varies widely by species, growth conditions, grain orientation, and previous moisture history. In general, tangential shrinkage exceeds radial shrinkage, and both are influenced by density and the proportion of latewood versus earlywood.

Measurements of shrinkage are usually expressed as percentages of the wood’s size at target moisture states, such as oven-dry. Typical values differ by species, but the pattern—tangential greater than radial; volume shrinkage being the result of both—holds across most woods. Engineering and construction practices often account for houtkrimp through proper drying schedules, acclimation to ambient conditions, and design allowances to prevent warping, cupping, or joint failure.

Mitigation strategies include controlled kiln or air drying, sealing end grains to reduce moisture exchange, and using joinery and layout that tolerate moisture-driven dimensional changes.