The term "timber" describes sawn wood that is 114mm(4-1/2") or more in its smallest dimension. There are two categories of timbers. Rectangular "Beams and Stringers" (larger dimension exceeds smaller dimension by more than 51mm (2")) are typically used as bending members, and square "Posts and Timbers" (larger dimension exceeds smaller dimension by 51mm (2") or less) are typically used for columns.
Wood timbers were widely used in traditional construction although they are less commonly used today. Materials available from lumber yard stock are usually sawn to order from large timbers and should be regarded after cutting. Because very big logs are required to obtain large timbers, the larger timbers most often come from the west. Sizes up to 394 x 394mm (15-1/2" x 15-1/2") are generally available in the Douglas Fir-Larch and Hem-Fir species combinations; however S-P-F and Northern species timbers are available only in smaller sizes. Availability of large size and long length timbers should always be confirmed with suppliers prior to specifying.
There has been little in-grade strength test data on timbers, due to the relatively small volume of timbers produced. Therefore, the design values for timbers continue to be determined on the basis of small clear testing adjusted for grade characteristics. Timbers, along with other materials, such as glulamand parallel strand lumber (PSL), are used in post and beam construction.
Timber.pdf (261 KB)