THE OWNER BUILT HOME & HOMESTEAD
(Page 11 of 13)
September/October 1972
By Ken Kern
Latex paints have proven to be the foremost choice for interior as well as exterior masonry surfaces. Styrene-butadiene (rubber latex) pioneered among latex paints in this country. It out-performs by far the best oil-based paints on the market. It is the least expensive of all latex paints and is best used on inside masonry basement walls, owing to its water-repellent and alkali-resistant qualities.
RELATED CONTENT
Cement-water paint has been the traditionally accepted waterproofing material for masonry surfaces, especially porous concrete block walls. The portland cement content should be not less than 65% by weight of the total paint. Fine, sharp silica sand and/or hydrated lime make up the balance. The paint must be applied to damp walls for proper adhesion.
Whitewash is an inexpensive, even older, and still used masonry coating. The National Lime Association suggests a formula having 5 lbs. of casein dissolved in 2 gals. of hot water, 3 lbs. of trisodium phosphate dissolved in 3 gals. of water, 3 pints of formaldehyde mixed in 3 gals. of water, all added to 8 gals. of lime paste (50 lbs. of hydrated lime mixed with 6 gals. of water). The lime coating is applied to damp walls, and dries to an opaque, hard, dust-free finish.
Polyvinyl acetate and acrylic have excellent color-retention and water-resistant qualities on outside masonry surfaces, asbestos cement, and asphalt shingles. Resin-based urethane is a new concrete floor varnish that is claimed to outlast other floor varnishes three to five times. Chlorinated rubber and phenolic are used where the floor is exposed to acids, alkalis, salt and other corrosive elements.
There are a number of factors that influence the proper choice of masonry paints. Cement-swater paints, for instance, are more suitable for new, and therefore damp, walls containing water-soluble alkaline salts and open-textured surfaces. Resin-emulsion paints are better for dry, close-textured surfaces such as cast concrete, asbestos-cement siding, tile, etc. Oil paints are best used on masonry surfaces that are dry at the time of painting and remain dry afterward.
Corrosion (rust) is a common problem when using exposed metal in building construction. Zinc-dust paint is about the only primer that will adhere satisfactorily to galvanized metal surfaces. In priming steel, "red lead," iron oxide, or zinc chromate in linseed, alkyd, or phenolic vehicles is satisfactory. A linseed or alkyd finish coat is then applied. The best preservant for tarpaper roofs is a commercial asphalt varnish mixed with aluminum powder. Upon application the aluminum flakes float to the surface and give a metallic finish. These paints combine excellent durability with reflective roof-coating features.
These recommendations on paint materials deal with only one small segment of the total painting problem. Equally important, a painter must understand the "paintable" characteristics of different surfaces. He must choose and use correctly the various tools of the trade. Finally, his method of procedure must be correctly established—such as painting the house exterior before the interior, and painting the ceiling before the walls before the woodwork before the floor before the baseboard.
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