Wash That Surface

sprayer PROPER PREPARATION for repainting depends on the condition of the surface. To remove mildew, dirt, and chalking, dissolve some trisodium phosphate (according to package instructions) in a solution of three parts water and one part bleach. Rent or purchase a pressure washer for this job, and select a hose tip that fans the water out in a flat stream about four inches wide. Wear protective clothing, gloves, and eyewear. Emphasize washing over pressure. Severe mildew, dirt, and chalking may require some scrubbing with a stiff-bristle brush. Rinse well and let any areas of bare wood dry thoroughly.
Resist temptation when you see low-pressure washing taking off loose paint that's flaking or peeling. If you boost the pressure to remove alligatored, cracked, or blistered paint, it can result in saturated wood and masonry, water behind the clapboards, soaked inner walls, knocked-off shingles, and blown-out stained-glass windows.