Problémy s drevom: Rozťahovanie a zmršťovanie dreva

The success of a woodworking project depends partly on whether you’ve allowed for wood expansion and shrinkage. Wood moves as it releases or absorbs moisture. That’s why it makes no sense to use freshly cut wood for a project: the wood will shrink significantly as it dries.

A living tree is full of moisture because many gallons of water move through it every day, from the roots to the branches and leaves, and some of that moisture is released into the atmosphere. The relationship between wood and the moisture in its environment continues after a tree is cut down. Wood adapts to the moisture level around it by either releasing moisture, which causes shrinkage, or absorbing moisture, which causes expansion.

Suché drevo na dosiahnutie rovnováhy

Most lumber manufacturers use kilns to dry lumber to the proper moisture levels for woodworking. Kiln drying uses heat to dry stacks of lumber. Lumber can also be air-dried, but the process is much slower. Handheld wood moisture meters make it easy to check the moisture level in a piece of lumber.

The goal is to dry wood to the moisture level it will reach in the environment where the finished product will be used or installed. Matching the wood to that environment, its equilibrium moisture content, minimizes movement.

Changes within an environment can still cause problems. In the upper Midwest, for example, summers are humid but winters are quite dry. Many homeowners use humidifiers in winter to add moisture back to the air so hardwood floors and furniture don’t dry out enough to be damaged. This kind of seasonal change in humidity is why dresser drawers and doors tend to stick in summer but work fine in winter.

Moving a piece of furniture to a very different climate is another consideration. A finely crafted hardwood chest of drawers that has reached equilibrium in a humid place like Louisiana could crack if it’s moved to a dry climate like Arizona, as the wood releases a substantial amount of moisture.

Pochopte, ako sa drevo rozpína

A skilled woodworker knows how the wood being used will move as it adjusts to the moisture in its environment. Almost all of that movement happens across the grain, not along it. Shrinkage along the grain from green to oven-dry is only about 0.1% to 0.2% for most species, according to the USDA Forest Products Laboratory’s Príručka o dreve. In other words, an 8-foot-long 2×4 will stay essentially 8 feet long, but its width and thickness can change significantly.

Bezplatné stiahnutie – 6 dôvodov, prečo váš projekt s drevom zlyhal

Stavajte s ohľadom na expanziu

If you’re building a cabinet, for example, it can help to use wood from the same original stock. In any case, orient the grain of the lumber in the same direction. Wood movement can affect drawers and make them hard to open. That’s one reason plywood is used for most cabinet carcasses: its alternating grain layers make it much more dimensionally stable along its length and width than solid lumber.

When you glue boards together for a tabletop, many woodworkers alternate the orientation of the growth rings on the end grain, with one board’s rings curving up and the next board’s curving down. If the boards cup, each one cups slightly in the opposite direction instead of the whole top cupping as one. Starting with properly dried wood is still the best way to limit cupping.

Zistite, prečo je dôležité vedieť, správny obsah vlhkosti pre vaše projekty spracovania dreva.

Vlhkomery Orion

Ron Smith

Ako obchodný manažér spoločnosti Wagner Meters má Ron viac ako 35 rokov skúseností s prístrojovou technikou a meracími systémami v rôznych odvetviach. V predchádzajúcich pozíciách pôsobil ako regionálny obchodný manažér, produktový a projektový manažér a obchodný manažér pre výrobcov zaoberajúcich sa meracími prístrojmi.

Posledná aktualizácia 8. októbra 2026