Figure 6-37-Roof or rafter truss.Figure 6-38.-Light wood trusses: A. W-type; B. King post;C. Scissors.shape of the letter W instead of a center post.The KING POST truss is the simplest type ofstructure. It consists of an upper and lower chordwith a vertical center post (fig. 6-38, view B). TheSCISSORS truss (fig. 6-38, view C) is used forstructures with sloped ceiling room, such as avaulted ceiling.BUILDING FINISHPerhaps the best way to define building finishis to say that it comprises those nonstructural partsof the building. The finish is divided intoEXTERIOR finish (located principally on theoutside of the structure) and INTERIOR finish(located inside). The work involved in theinstallation of nonstructural members on thestructure is called FINISH CARPENTRY.EXTERIOR FINISHThe principal items of the exterior finish arethe ROOF SHEATHING and COVERING,EXTERIOR TRIM, and WALL SHEATHING.The order in which these items are erected mayvary slightly, although in some cases two or moreitems may be installed at the same time.Normally, roof sheathing is installed as soon aspossible to allow work inside a structure toprogress during inclement weather.Roof Sheathing and Roof CoveringRoof sheathing is the covering over the raftersor trusses and usually consists of nominal 1-in.lumber or plywood. In some types of flat or low-pitched roofs, wood roof planking or fiberboardroof decking might be used. Sheathing should bethick enough to span the supports and providea solid base for fastening the roofing materials.Generally, third grade species of lumber, such aspines, redwoods, and hemlocks, are used as roofsheathing boards.Board roof sheathing (fig. 6-39) used underasphalt shingles, metal sheet roofing, or otherFigure 6-39.-Typical board roof sheathing, showing bothclosed and spaced types.6-27
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