Copyright Goodheart-Willcox Co., Inc. 122 Section 3 Specifications and Materials and bending. It also has excellent impact resistance. While steps have been taken to substitute other materials, wood remains a valuable and widely used residential construction material. Wood Classification Woods are broadly classified as either hardwoods or softwoods. There are many varieties used for construc- tion. These classifications are not an exact measure of hardness or softness (because this varies) but a general classification based on type of tree. In addition to hardness or softness, woods vary in strength, weight, texture, workability, and cost. Building specifications usually indicate the type and grade of lumber to be used in different parts of the construction. Wood Classifications Hardwoods Softwoods Ash h Cypr re ss yp A As h, Wh W hi te Fir, Do ou glas g Beech h Fir, W Wh ite Birch h h Heml lo ck Cherry r Pine, i Pon nd erosa a y Elm m Pine, P So ou thern n Gum m m Pine, White W Hickory or Poplar, P Yellow Y y p M Ma hogany ga Red d Cedar r, Eastern g g y Maple l e Red d Cedar, r Weste er n p Oak k Redw wo od Walnu n ut Spruce u p Lumber When wood is cut into pieces of specific thickness, width, and length, it is called lumber. Lumber products r r include rough framing members (at least 2″ thick), such ″ as beams, headers, and posts finished lumber, such as flooring, door and window trim, paneling, and moldings and specialty items, such as decorative panels, carved doors, ornamental overlay designs, and turned balusters (stair-rail posts). Lumber is classified as rough-sawn or surfaced to size. Rough-sawn lumber has been cut to size but not r dressed or surfaced. Surfaced lumber has been dressed r or finished to size by running it through a planer. The designation “S2S” is used for lumber dressed on two sides, and “S4S” for lumber that is surfaced or planed on all four sides. Plywood is a wood product made of several layers of d lumber arranged with the grain at right angles in each successive layer and bonded with an adhesive. An odd number of layers is used, so that the grain of the face and back are running in the same direction. The panels are Division 06—Wood, Plastics, and Composites Wood continues to be one of the chief building materials, Figure 7-22. It is used for structural framing (rough carpentry), trim, floors, walls, and cabinetry (finish carpentry and architectural woodwork). Relative to its weight, wood has high strength in compression, tension, Norris & Dierkers Architects/Planners, Inc. A Steel column Steel beam B Jim Parkin/Shutterstock.com Figure 7-20. A—This steel frame is designed to support the entire weight of the building. The exterior walls of this building are precast concrete panels. B—Steel beams and columns are common members used to support a building. Connections between the structural members are specified on detail drawings. Goodheart-Willcox Publisher