More than two dozen species of wood are commonly used to build log homes in North America. Almost all are softwoods: evergreens such as pine, cedar, fir, cypress, hemlock and spruce. Although each log home producer favors certain species, the successful use of so many varieties is a clear indication that there’s not one type of tree that makes a better log home than another. Instead, the choice rests in the type of wood your log home company and you prefer. Despite their many differences, these various woods share certain characteristics.
Technically, wood is the hard, fibrous substance beneath the bark in a tree. It owes its character to the hollow, elongated, spindle-shaped cells that constitute it. These cells are arranged parallel to each other along the trunk of a tree, and this arrangement affects some properties of the wood, notably strength and shrinkage. The wood’s fibrous nature influences how it is used.
Trees grow by adding new wood. Wood that has already been formed does not continue to grow, but each year, a new layer of wood, called an annual growth ring, is added. The portion of the ring formed in the spring is light in color and is called earlywood. The portion formed later in the growing season is darker and is called latewood. Latewood is generally denser and stronger than earlywood.
The wood formed just inside the bark is known as sapwood. Depending on the size and species of the tree, sapwood can measure one to three inches beneath the bark. As a rule, the more vigorously growing tree species have wider sapwood layers. Second-growth trees of marketable size consist mainly of sapwood.
Sapwood contains mostly living cells that carry sap, the tree’s food, from the roots to the leaves. It’s not durable, and if exposed to moisture and other factors, it can decay. But in terms of log home construction, sapwood usually absorbs preservatives readily, so when wood is impregnated with a good wood preservative, the presence of sapwood can be an advantage. If thoroughly treated, sapwood will usually be at least as decay resistant as the treated heartwood, maybe more so.
Inside the sapwood is the heartwood. Heartwood consists of inactive wood cells that have been changed slightly, both chemically and physically, so that they no longer conduct sap. Heartwood is usually more decay resistant than sapwood.