WOOD-SELECTION Rules Help But Should Not Be Followed Blindly

The following rules for the selection of wood should be used only as rough guides and not as substitutes for specific information, such as may be obtained from the Forest Products Laboratory, Madison, Wis. Exceptions to most of them can be found, and if a large amount of material is involved or if the wood is to be used for some important purpose, dependence on these rules alone is inadvisable; additional information should be obtained.

Sapwood is the outer portion and heartwood the center portion of a cross section of a log. The sapwood is usually lighter in color than the heartwood.

Springwood is the thin-walled, relatively weak, and usually light-colored portion and summerwood the thick-walled, heavy, and relatively strong portion of the ring that grows annually in the tree.

The term “softwoods” is applied to the group of trees that bear cones, examples of which are pine and spruce; "hardwoods" is applied to broad-leaved trees, such as oak and maple. Actually some softwoods are harder than some woods of the hardwood group.

Dense wood is heavy and hard; hickory is an example.

The term "heavy" is used in defining the actual wood substance apart from any moisture it may contain. Even a light wood may have much weight if it is saturated with water.

Heavy woods have high fuel value.

Seasoning wood increases its fuel value.

The heat value of 1 cord of heavy wood, 1½ cords of medium-heavy wood, or 2 cords of light wood is approximately equivalent to that of a ton of coal.

Softwoods generally burn more readily than hardwoods, light woods more readily than heavy woods.

Heartwood is generally more durable than sapwood of the same species.

Pitchy wood is more durable than nonpitchy wood of the same species.

Dark woods are usually more durable than light-colored woods.

Wood properly treated with a preservative is many times as durable as untreated wood.

The time of year when timbers are cut has no great effect upon their resistance to decay if they are properly cared for after cutting.

Wood is not effectively protected from decay by painting.

Posts or timbers with the bark on decay more rapidly than peeled posts or timbers.

Heavy wood is generally hard and strong, light wood soft and weak.
Heavy wood holds nails well, but tends to split in nailing.

Seasoned wood holds nails better than green wood.
Seasoned wood is stronger than green wood, except in shock resistance.

The growth change from sapwood to heartwood in the wood of the tree does not affect the strength.

Timber of the same species grown in widely different localities generally varies no more in strength than timber of the same species grown in one locality.

Woods of light weight are better temperature insulators than heavy woods.

Woods with prominent alternate annual growth rings of soft spring wood and hard summer wood are more difficult to work than woods either uniformly soft or hard.

Softwoods generally require less care in gluing than heavy woods.