Formula for Killing Moss on a Roof

Cleaning the Roof

• Clean your roof of any debris that might act as food or protection for the moss, including any leaves or broken tree limbs. "Popular Mechanics" recommends a product called Moss Aside, which kills moss and cleans away debris still clinging to the roofing materials. Tim Carter of Ask the Builder suggests powdered oxygen bleach mixed with water, which works the same way. Cover the roof with a thin layer of cleaning solution and gently work it across the shingles, using a scrub brush or mop. Once you clean the roof completely, use a pressure washer or sprayer and rinse off any residue.

Considerations

• When cleaning the moss off the roof, look at the shingles and move in the direction of those shingles. More than likely, you must work from the top or peak of the roof down to the walls of the house. When you clean against the shingles, you risk knocking loose a few shingles or causing other damage to the roof. Follow the same path when rinsing off the roof.

Prevention

• Examine the sides of the roof carefully, looking for any trees close to the top of the house. Trim tree branches that overhang the roof, as those branches provide dark, shady spots that foster moss growth. According to both Carter and "Popular Mechanics," zinc strips prevent moss growth in the future. Lay one strip along the peak or center of the roof and add more strips along the sides. When rain hits the strips, it sends zinc carbonate to different areas of the roof, stopping the moss from growing and coming back.

Warning

• Don't use full-strength liquid bleach on your roof. The runoff from the bleach bleeding into your yard can kill any vegetation near the sides of the house, including grass, plants and trees. Avoid using laundry detergent to kill moss, as it isn't effective.