Lumber is classified according to its USE, SIZE, and EXTENT OF MANUFACTURE. When classified according to use, lumber falls into three categories:

1. YARD LUMBERgrades, sizes, and patterns generally intended for ordinary construction and general building purposes

2. STRUCTURAL LUMBER2 or more in. in thickness and width for use where workingstresses are required

3. FACTORY AND SHOP LUMBER produced or selected mainly for manufacture of furniture, doors, cabinets, and other millwork

Table 6-1.-Common Woods

Table 6-1.-Common WoodsContinued

Table 6-1.-Common WoodsContinued

Table 6-1.-Common WoodsContinued

Table 6-1.-Common WoodsContinued

Nominal, rough, green lumber has three general classifications, according to size, as follows:

2. DIMENSIONat least 2 in. thick, but less than 5 in. thick, and 2 or more in. wide. It may be classified as framing, joists, planks, rafters, studs, and small timbers.

3. TIMBERSsmallest dimension is 5 or more in. They may be classified as beams, stringers, posts, caps, sills, girders, and purlins. Lumber classified by extent of manufacture consists of three types as follows:

1. ROUGH LUMBER is not dressed (sur-faced) but sawed, edged, and trimmed to the ex-tent that saw marks show in the wood on the four longitudinal surfaces of each piece for its overall length.

2. DRESSED LUMBER is surfaced by a planing machine to attain a smooth surface and uniform size.

3. WORKED LUMBER is dressed and also matched, shiplapped, or patterned.