The result will be a structure having the strength and durability of masonry with a popular, attractive stucco finish. With the right planning and preparation in the construction of the concrete masonry base, the final step is to follow the requirements of ASTM C 926, the Standard Specification for Application of Portland Cement Plaster, and the guidelines given in PCA's Portland Cement Plaster (Stucco) Manual EB049 in applying the plaster. A dash bond coat is a slurry mixture rich in cement, usually one part cement to no more than two parts sand, that is literally dashed against the wall using a brush, trowel, paddle, or machine. If open textured masonry units are not available or the condition of the masonry surface is questionable, apply a dash bond coat of a non-re-emulsifiable bonding agent to masonry surfaces prior to application of the basecoat. However, avoid saturating the masonry either by excessive spraying or by exposure of uncovered masonry walls or units to rain. Prior to application of the basecoat, uniformly pre-moisten concrete masonry surfaces to aid in curing of the plaster. Plaster is applied to concrete masonry surfaces in two or three coats, consisting of basecoat(s) and a finish coat. Because plaster and concrete masonry undergo similar volume changes, place control joints in the plaster only in locations that coincide with control joints in the concrete masonry. Cut all mortar joints flush, rather than tooling or sponge floating them. To enhance that inherent compatibility, select open-textured concrete masonry units that promote mechanical keying between the plaster and the base masonry wall. Traditional portland cement stucco should not be confused with the Exterior Insulation Finish Systems (EIFS) which are sometimes called "synthetic stuccos."Ĭoncrete masonry provides an excellent base for direct application of portland cement plaster. The term "stucco" is widely used to describe material applied to exterior surfaces. Portland cement plaster and portland cement stucco are the same material. Sea sand is prohibited for construction work, because of high salt contents. Sand should be clean, free from dust and organic matters. Size of sand particles should be such that it passes through 4.75mm sieve. Sand particles should have coarse, sharp and angular edges. The serviceability of traditional portland cement plaster has been proof-tested through long use in extreme environments such as the cold temperatures of Alaska and Canada, the hot temperatures of the humid Gulf States, and the dry Southwestern States. Sand is used as fine aggregate in cement concrete. Portland cement plaster is a versatile, durable facing material that can be applied to either exterior or interior surfaces of a structure.
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