Table 7-1.—Base Coat Proportions for Different Types of Workof lime putty, or 94 pounds (one sack) of portlandFINISH COAT PROPORTIONS.— A lime finishcement. One part of aggregate means 100 pounds ofsand or 1 cubic foot of vermiculite or perlite. Note:Vermiculite and perlite are not used with lime plaster.While aggregate parts given for gypsum or portlandcement plaster may be presumed to refer to either sandor vermiculite/perlite, the aggregate part given for limeplaster means sand only.BASE COAT PROPORTIONS.— Two-coatplasterwork consists of a single base coat and a finishcoat. Three-coat plasterwork consists of two base coats(the scratch coat and the brown coat) and a finish coat.Portland cement plaster cannot be applied to agypsum base. Lime plaster can, but, in practice, onlygypsum plaster is applied to gypsum lath as a base coat.For two-coat work on gypsum lath, the recommendedbase coat proportions for gypsum plaster are 1:2.5. Fortwo-coat work on a masonry (either monolithic concreteor masonry) base, the recommended base coatproportions are shown in table 7-1. Also shown in table7-1 are proportions for three-coat work on a masonrybase and proportions for work on metal lath.PlasterFor three-coat work on gypsum lath, the recom-mended base coat proportions for gypsum plaster areshown in table 7-2.can be applied over a lime, gypsum, or portland cementbase coat. Other finishes should be applied only to basecoats containing the same cementitious material. Agypsum-vermiculite finish should be applied only to agypsum-vermiculite base coat.Finish coat proportions vary according to whetherthe surface is to be finished with a trowel or with a float.(These tools are described later.) The trowel attains asmooth finish; the float produces a textured finish.For a trowel-finish coat using gypsum plaster, therecommended proportions are 200 pounds of hydratedlime or 5 cubic feet of lime putty to 100 pounds ofgypsum gauging plaster.Table 7-2.—Recommended Base Coat Proportions for Gypsum7-10
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