Metal LathAll metal lath is installed with the sides and endslapped over each other. The laps between supportsshould be securely tied, using 18-gauge tie wire. Ingeneral, metal lath is applied with the long length at rightangles to the supports. Rib lath is placed with the ribsagainst the supports and the ribs nested where the lathoverlaps. Generally, metal lath and wire lath are lappedat least 1 inch at the ends and 1/2 inch at the sides. Somewire lath manufacturers specify up to 4 1/2-inch endlapping and 2-inch side laps. This is done to mesh thewires and the paper backing.Lath is either nailed, stapled, or hog-tied (heavywire ring installed with a special gun) to the supports at6-inch intervals. Use 1 1/2-inch barbed roofing nailswith 7/16-inch heads or 1 inch 4-gauge staples for theflat lath on wood supports. For ribbed lath, heavy wirelath, and sheet lath, nails or staples must penetrate thewood 1 3/8 inches for horizontal application and at least3/4 inch for vertical application. When common nailsare used, they must be bent across at least three lathstrands.On channel iron supports, the lath is tied with No.18-gauge tie wire at 4-inch intervals using lathers’nippers. For wire lath, the hog tie gun can be used. Lathmust be stretched tight as it is applied so that no sags orbuckles occur. Start tying or nailing at the center of thesheet and work toward the ends. Rib lath should haveties looped around each rib at all supports, as the mainsupporting power for rib lath is the rib.When you install metal laths at both inside andoutside corners, bend the lath to forma comer and carryit at least 4 inches in or around the corner. This providesthe proper reinforcement for the angle or comer.Lath AccessoriesA wide variety of metal accessories is produced foruse with gypsum and metal lathing. Lathing accessoriesare usually installed before plastering to form truecorners, act as screeds for the plasterer, reinforcepossible weak points, provide control joints, andprovide structural support.Lathing accessories consist of structural com-ponents and miscellaneous accessories. The principaluse of structural components is in the construction ofhollow partitions. A hollow partition is one containingno building framing members, such as studs and plates.Structural components are lathing accessories that takethe place of the missing framing members supportingFigure 7-6.—Perforated flanged corner bead.the lath. These include prefabricated metal studs andfloor and ceiling runner tracks. The runner tracks takethe place of missing stud top and bottom plates. Theyusually consist of metal channels. Channels are alsoused for furring and bracing.Miscellaneous accessories consist of componentsattached to the lath at various locations. They serve todefine and reinforce comers, provide dividing stripsbetween plaster and the edges of baseboard or othertrim, and define plaster edges at unframed openings.Comer beads fit over gypsum lath outside cornersto provide a true, reinforced comer. They are availablein either small-nose or bullnose types, with flanges ofeither solid or perforated (fig. 7-6) metal. They areavailable with expanded metal flanges.Casing beads are similar to comer beads and areused both as finish casings around openings in plasterwalls and as screeds to obtain true surfaces around doorsand windows. They are also used as stops between aplaster surface and another material, such as masonry orwood paneling. Casing beads are available as squaresections, modified-square sections, and quarter-rounds.Base or parting screeds are used to separate plasterfrom other flush surfaces, such as concrete. Ventilatingexpansion screed is used on the underside of closedsoffits and in protected vertical surfaces for ventilationof enclosed attic spaces. Drip screeds act as terminatorsof exterior portland cement plaster at concretefoundation walls. They are also used on externalhorizontal comers of plaster soffits to prevent drip stains7-7
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