When you prepare an engineering drawing, regardless of type, you are required to apply knowledge of the materials and methods of construction. This chapter describes the uses, kinds, sizes, grades, and other classifications of wood as they apply to light frame building construction; the various structural members and their functions; and the different types of finishing hardwares and fasteners used.

Of the different construction materials, wood is probably the most often used and perhaps the most important. The variety of uses of wood is practically unlimited. Few SEABEE construction projects, whether involving permanent or temporary structures, are built without using wood. Temporary uses of wood include scaffolding, shoring, bracing, and miscellaneous concrete forms.

There are several types or species of wood. Each type has its own characteristics and its recommended uses. For most large projects, the types and classifications of wood are given in the project specifications. For smaller projects that DO NOT have written specifications, the types and classifications of wood are included in the drawings. The types, sources, uses, and characteristics of common woods are given in table 6-1. In addition, the species, size classification, and design values of common structural woods are also listed in the Standards.

In construction, the terms wood, lumber, and timber have distinct, separate meanings. WOOD is the hard, fibrous substance that forms the major part of the trunk and branches of a tree. LUMBER is wood that has been cut and surfaced for construction use. TIMBER is lumber whose smallest dimension is NOT less than 5 in. Another term, MILLWORK, refers to manufactured lumber products, such as doors, window frames, window casings, shutters, interior trim, cabinets, and moldings.

Standard lumber sizes have been established in the United States to permit uniformity in planning structures and in ordering materials. Lumber is identified by NOMINAL SIZES. The nominal size of a piece of lumber is larger than the actual DRESSED dimensions. Dressed lumber has been SURFACED (planed smooth) on two or more sides. It is designated according to the number of sides or edges surfaced. If it has been surfaced on two sides only, the designation is S2S (surfaced 2 sides); if surfaced on all four sides, S4S (surfaced 4 sides); or if surfaced on two sides and two edges, S2S2E. Lumber is ordered and designated on drawings by its nominal size rather than by its dressed dimensions. Common widths and thicknesses of lumber in nominal and dressed dimensions are shown in table 6-2.