Sizes of Structural Lumber

Most structural lumber is called dressed lumber. In other words, the lumber is surfaced to the standard net size, which is less than the nominal, or stated, size. This is shown in Figure 3.3.

Dressed lumber is used in many structural applications. How­ever, some architectural applications may call for larger members that have a different texture. Such members are commonly rough – sawn to dimensions that are close to the standard net size. The cross-sectional dimensions of these timbers is about 1/8 in. larger

Sizes of Structural Lumber

Figure 3.3 Example of sizes of structural lumber.

 

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than the standard dressed size. A less common method of ob­taining a rough surface is to specify full-sawn lumber. Since rough – sawn and full-sawn lumber are not frequently used, their cross­sectional properties are not included in the NDS.

Below is an example of the differences between nominal, dressed, rough-sawn, and full-sawn sizes of lumber. Consider an 8 x 12 member (nominal size = 8 x 12 in.):

1. Dressed lumber: Standard net size 7xk x 11/2 in.

2. Rough-sawn lumber: Approximate size 75/8 x 115/8 in.

3. Full-sawn lumber: Minimum size 8 x 12 in. (generally not available).