Some popular cleansers include Wet & Forget, a spray-on product for removing moss, mold, and mildew; Bayer 2-in-1 Moss and Algae Killer, a potassium soap of fatty acids and inert ingredients that you mix with water and then spray on; and Moss B Ware, a 99 percent zinc sulfate monohydrate powder that can be applied dry or mixed with water. Whichever you choose, follow the manufacturer’s directions for application; some cleansers should be rinsed off after use, while others specify to be left on. You also can make your own moss remover in a large spray bottle with one of these four DIY recipes: • 8 ounces Dawn Ultra dish soap + 2 gallons of water • 1 pound powdered oxygen bleach + 2 gallons of water • 1½ to 3½ cups chlorine bleach + 2 gallons of water • 1½ to 3½ cups white distilled vinegar + 2 gallons of water For any of these homemade options, you’ll want to wet down the roof with plain water first, then apply the cleanser and let it sit for 20 to 45 minutes. Lightly scrub with a soft-bristle brush, then rinse with water.

STEP 3 Prevent a moss problem from returning by installing strips of zinc- or copper-coated sheet metal just below the top ridge on both sides of the roof. Copper is more toxic to moss and algae, but zinc is much less expensive. You can purchase sheet metal in rolls and cut it into two- to four-inch strips. Attach the strips to the roof using roofing nails or screws with a rubber washer. You also should consider pruning any tree limbs that overhang the roof—natural sunlight is a powerful moss preventive. Cleaning roof shingles is not something that many people think about. However, it should be done at least every few years, especially if there are any large trees that hang over the roof. Small leaves or seeds fall onto the roof and can germinate over time. Washing the roof down prevents this from happening. Some cleaners are better than others for this process. Knowing which ones to use will help keep the shingles clean and long lasting.