Fundamental Properties

Basic Wood Structure: Surfaces of Wood

Before beginning a study of wood, it is first necessary to understand that wood looks different depending upon which surface is viewed.
Cross section or transverse surface

The surface that is viewed when looking at the end of a log or the top of a stump is known as a cross section. This surface is also sometimes referred to as a transverse surface.

Heartwood and sapwood zones, annual growth rings and rays can be seen on this surface.

Close examination of a cross section or transverse surface, shown here as the top of a wedge-shaped portion of a round cross section, clearly reveals annual growth rings.
Radial surface

The surface created by cutting along a radius of a round cross section is known as a radial surface.

Tangential surface

The surface created by cutting at a tangent to the growth rings, or the surface you would see if you were to view the outside of a log with the bark removed, is called the tangential surface.

To summarize: three distinct surfaces of wood can be identified: cross section, radial, and tangential.

As you will later learn, wood not only looks different in cross section, radial, and tangential views, but it also has considerably different properties depending upon its orientation.

(Images adapted from: Haygreen, J.G. and Bowyer, J.L., Forest Products and Wood Science - An Introduction, 3rd ed., 1996. Iowa State University Press.) Softwoods Home Orders
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