Removing Stains From Asphalt Shingles

If you have shingles made of asphalt, you may have noticed stains that have developed on your roof. These unsightly black streaks can make your roof look dirty and beat up even if the shingles on your roof aren't very old. Regardless of how recently your roof has been reshingled, these dark stains might make you think about replacing your roof shingles just to make your roof look nice again.

These streaky stains are usually caused by a kind of algae that thrives in humid regions. Roof shingles introduced within the last twenty years are more likely to attract an algae problem, because they are made of different materials that the algae thrive on. This algae loves the materials in your asphalt roof and live and grow on the shingles. The black you see accumulating on the roof over time is dead cells from these algae.

The good news is that you don't have to replace your roof to get it looking new again. Instead, you can clean the roof and take measures to prevent future algae problems. With the right knowledge and materials, you can clean the shingles yourself.

• Choose a cleaner for your roof. There are different options you can buy that are made specifically for getting algae off your roof. Follow the directions for the product carefully.
• You can also use an oxygen bleach (not chlorine) powder that you can mix with water. If you try this method to clean your roof, it is best to do it on a cloudy day so that the mixture won't dry too quickly. Mix the bleach with water (about one quart of bleach to one gallon of water) and 3 ounces trisodium phosphate (which can be found in hardware stores) and put in a garden sprayer. Get the roof wet with the mixture, then let sit for about fifteen minutes or so. Use a hose to rinse it off.
• To stop the algae from returning, try installing some sheet metal that is coated with either zinc or copper below the roof's ridge on both sides. Zinc and copper are toxic to the algae and will help to keep it from coming back.

Always use caution when cleaning your roof yourself. Be sure that the ladder you use to climb up onto the roof is secure and stable. When on the roof, be aware of slippery conditions caused by water. You might want to consider wearing some kind of safely harness to prevent slipping.