Cuts of Lumber and Effects on Stability

Because fresh cut wood is two thirds it weight in moisture, as the wood dries out it will change shape. Wood will lose moisture and seek its equilibrium moisture content with the environment, and once it reaches that equilibrium, it will fluctuate seasonally with changes in the relative humidity of it’s surroundings. When a board is cut from a tree, it’s length is cut parallel to the trunk, so that the strength of the grain be aligned with the length of the board. However, the grain pattern at the end of the board can follow one of three patterns and it provides insights into its future behavior.

Plainsawn lumber is sliced right off of the log. If growth rings were straight, they would appear parallel, or nearly so, to the face of the board from the end grain. It is probably the easiest and cheapest wood to produce, but it is also the least stable and is prone to cupping and warping. The grain can also be fairly wild. But how can we tell about the cupping in advance?

The easiest way to remember is that growth rings, as they dry, want to flatten out into straight lines. If you see a U-shaped growth ring pattern when looking at the end grain, you know that the edges of the face will want to cup down and straighten, thus the board will frown. However, not all lumber has to suffer this fate.

Riftsawn lumber, often found near the ends of plainsawn boards, has growth rings at a thirty to sixty degree angle to the face. It is generally clearer, has straighter grain and is much less likely to warp. It is usually found in the same pile as the flatsawn lumber and often as part of the same board. This is where creative breakdown of the rough lumber can select out the riftsawn cuttings (useable boards cut from raw lumber) so you can put its characteristics to best use.

Finally, quartersawn lumber is identified by growth rings perpendicular to the face of the board. It has the straightest grain, is the least likely to warp or cup, and is the best lumber you can buy. Of course you pay for it too, as more waste is created when cutting quartersawn boards than when sawing any others. Bigger logs are also needed to get wider boards and that will add to the price per board foot. On the bright side, the rays stand out more and contribute to a high degree of figure in the finished material.