Document v9v2MpEjQ0LjELbrOqq75D8R

U.S. DEPARTMENT OF AGRICULTURE FOREST SERVICE FOREST PRODUCTS LABORATORY MADISON, WIS. In Cooperation with the University of Wisconsin U.S.D.A. FOREST SERVICE RESEARCH NOTE FPL - 0232 1976 HOW TO REFINISH WOOD SIDING WITH LATEX PAINTS By EDWARD A. MRAZ, Technician Forest Products Laboratory,1 Forest Service U.S. Department of Agriculture SUMMARY Every homeowner with painted wood siding and trim at some time faces the job of repainting. In this Note a simple test is described to determine whether an old sur- face will form a satisfactory bond with latex paints, and suggestions are given on preparing the surface to achieve a satisfactory bond, INTRODUCTION Weathering is the action of sun, wind, rain, dew, snow, hail, and dust. On painted wood siding and trim, weathering gradually causes the best quality paint to wear away, and the siding must be repainted. Repainting is a major job for the homeowner. Thus, it is worthwhile to learn how to extend intervals between paintings. The purpose of this Note is to outline the procedures to follow to attain a durable paint surface on wood siding. However, if water or moisture is getting behind siding, this must be prevented before repainting. This water or moisture in walls could be from inade quate vapor barriers, ice dams, leaky roofs, and poor gutters and downspouts. Repainting should be considered only after previous paint has weathered so that it no longer covers and protects the wood. Repainting too frequently can lead to a too thick paint film that causes paint failure. Maintained at Madison, Wis., in cooperation with the University of Wisconsin. 1- - PREPARATION OF SURFACE The following six steps should be help ful in preparing for repainting. (1) Scrape off all loose paint. (2) Sand bare spots and feather the edges of surrounding paint. (3) Remove chalk from old paint with steel wool or with sponge and detergent solution. (A chalk-free surface ensures a good bond between old and newly applied paint surfaces.) Rinse old paint thoroughly with water from a garden hose. (4) Brush all exposed wood and joints with a water-repellent preservative. (5) After 2 or 3 days of sunny, dry weather, apply an oil-base primer paint to bare spots to completely obscure the gram. (6) Calk all open joints and cracks with a synthetic calking compound. TEST FOR CHALKING A simple, helpful test has been devised to determine if a surface of old paint film is free of chalk and suitable for repainting. A small area of old paint surface is coated with latex paint, and the paint allowed to dry 24 hours or more. To test for adhesion, firmly press one end of an adhesive type of tape about 2-3/4 inches long by 1 inch wide (like that used with a gauze pad for covering minor wounds) onto the dry, freshly painted surface. With draw it quickly. If the tape is free of paint, the latex paint is well bonded to the old surface, and repainting can be started. If the new latex paint adheres to the tape, this indicates the old surface is still too chalky. If this is the situation, an oil-base primer coat should be applied. APPLICATION OF PAINT After the old paint surface has been prepared satisfactorily, apply two coats-ac- cording to directions given by the paint manufacturer. Avoid painting late in the evening-about 2 hours before sunset. Heavy dews are likely to form and cause water marks on the paint. Avoid painting if temperature is likely to fall below 50F during the night. If latex paint is applied on hot, dry, windy days in direct sunlight, dampen the area about to be painted by using a water-soaked sponge. This will improve paint spreadability, and the latex paint will not dry too quickly. Finally, always use a hiah-qualitv ex terior latex paint; quality is usually related to price. 2- - 4.5-2-2-76