three equal parts. Each short web meets the top chord ata point that is one-fourth the horizontal distance of thebottom chord.FABRICATIONThe construction features of a typical W-truss areshown in figure 2-64. Also shown are gusset cutout sizesand nailing patterns for nail-gluing. The span of thistruss is 26 feet and roof cut is 4/12. When spaced24 inches apart and made of good- quality 2- by 4-inchmembers, the trusses should be able to support a totalroof load of 40 pounds per square foot.Gussets for light wood trusses are cut from 3/8- or1/2-inch standard plywood with an exterior glue line, orfrom sheathing-grade exterior plywood. Glue is spreadon the clean surfaces of the gussets and truss members.Staples are used to supply pressure until the glue is set.Under normal conditions and where the relativehumidity of air in attic spaces tends to be high, aresorcinol glue is applied. In areas of low humidity, acasein or similar glue is used. Two rows of 4d nailsare used for either the 3/8- or 1/2-inch-thick gusset. Thenails are spaced so that they are 3 inches apart and3/4 inches from the edges of the truss members. Gussetsare nail-glued to both sides of the truss.Plywood-gusset, king-post trusses are limited tospans of 26 feet or less if spaced 24 inches apart andfabricated with 2- by 4-inch members and a 4/12 roofcut. The spans are somewhat less than those allowed forW-trusses having the same-sized members. The shorterspan for the king-post truss is due, in part, to theunsupported upper chord. On the other hand, because itdistances between connections are shorter, the W-trusscan span up to 32 feet without intermediate support, andits members can be made of lower grade lumber.INSTALLATIONTrusses are usually spaced 24 inches OC. They mustbe lifted into place, fastened to the walls, and braced.Small trusses can be placed by hand, using the procedureshown in figure 2-69. Builders are required on the twoopposite walls to fasten the ends of the trusses. One ortwo workers on the floor below can push the truss to anupright position. If appropriate equipment is available,use it to lift trusses into place.In handling and storing completed trusses, avoidplacing unusual stresses on them. They were designedto carry roof loads in a vertical position; thus it isimportant that they be lifted and stored upright. If theymust be handled in a flat position, enough supportshould be used along their length to minimize bendingdeflections. Never support the trusses only at the centeror only at each end when they are in a flat position.BracingAfter the truss bundles have been set on the walls,they are moved individually into position, nailed down,and temporarily braced. Without temporary bracing, atruss may topple over, cause damage to the truss, andpossibly injure workers. A recommended procedure forbracing trusses as they are being set in place is shownin figure 2-70. Refer to the figure as you study thehas more members than the king-post truss andfollowing steps:Figure 2-70.—Installing roof trusses and temporary bracing.2-43
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