Composition wallboard usually presents no particular painting difficulties if the ordinary precautions are observed, such as making certain that the surface is dry and free from grease and oil. The painting procedure for wallboard is the same as for plaster; it requires a priming and sealing coat followed by whatever finishes coats are desired, or may be given one-coat flat or resin-emulsion type paint.
Water-thinned paint may be applied to wallpaper that is well- bonded to the wall and does not contain dyes which may bleed into the paint. One thickness of wallpaper is preferable for paint application. Paints other than those of the water-thinned type may also be applied to wallpaper by following the directions given for painting plaster. However, wallpaper coated with such a paint is difficult to remove without injury to the plaster.
Wood Walls and Trim
New interior walls and wood trim should be smoothed with sand-paper and dusted before painting or varnishing. To preserve the grain of the wood, the surface may be rubbed with linseed oil, varnished or shellacked, and waxed. If an opaque finish is desired, semi-gloss paint thinned with 1 pint of turpen-tine per gallon of paint or the primer-sealer previously described for walls may be used as a priming coat on wood. One or two coats of semi-gloss paint should then be applied over the thoroughly dry prime coat, or if a full-gloss finish is desired, the last coat should be a high-gloss enamel.
Masonry Walls and Ceilings
Interior masonry walls and ceilings above grade may, in general, be painted in much the same manner as plaster surfaces. Here again, it is necessary to allow adequate time for the masonry to dry before applying paint and, in addition, attention should be given to the preparation of the surface. When decorating a wall containing Portland cement (concrete, for example), it is essential to take precautions against the attack of alkali. For this purpose, alkali-resistant primers such as rubber-base paints may be used when oil paints are to follow.
Cement-water paints are best suited for application to basement walls which are damp as a result of leakage or condensation. To apply these paints, the same procedure should be followed as is described here for painting exterior masonry walls.
Two general types of paints for concrete floors are varnish and rubber-base paint. Each has its limitations and the finish cannot be patched without the patched area showing through. Floor and deck enamel of the varnish type gives good service on concrete floors above grade where there is no moisture present.
Rubber-base paints, which dry to a hard semi-gloss finish, may be used on concrete floors below grade, providing the floor is not continually damp from seepage and condensation.
Paint should not be applied to a concrete basement floor until the concrete has aged for at least a year. The floor should be dry when painted, the best time for application being during the winter or early spring (assuming there is some heating apparatus in the basement), when the humidity in the basement is low. In general, three coats of paint are required on an unpainted floor, and the first coat should be thin to secure good penetration. After the paint is dry, it should be protected with a coat of floor wax.