You know you need to clean your roof, but is one way to clean it better than another? Yes, there certainly are ways to clean your roof that will damage it and others that will help.
So let’s say you have a mold or algae problem on your roof, and that’s what you are trying to remove. If you have either in your home, usually a good way to clean it is bleach. Bleach kills it, removes the stains, done. Not so fast with your roof. Bleach can kill your landscaping around the house, covering the plants and shrubs will protect them. If the algae aren’t completely killed it will come back twice as strong. It’s like trying to get rid of weeds by cutting them. Exposure to pure bleach is damaging to most surfaces and your roof is no exception. Make sure your contractor uses a diluted solution if you have asphalt shingles, other alternatives like lye or sodium hydroxide are seriously damaging. Lye can even dissolve roofing nails if used at a concentration that is too high.
Ok, so no chemicals and a pressure washer? Not so fast. High pressure washing causes damage to most types of roofing materials. Another problem with high pressure washing is it can aerosolize mold spores and spread them to other parts of the roof or to your neighbor’s roofs. That means the problem is just spread, not stopped. Plus your neighbors probably won’t appreciate it either!
What you can do is to contact a roofing professional about the safest ways to clean your roof. There are lower pressure systems that work well. There are also things you can do to prevent re-infestation of mold or algae. One way is to install zinc strips near the peak of your roof. What this does is cause small amounts of zinc to dissolve when it rains. The zinc coats the roof and inhibits the growth of algae and molds. If you need to replace your roof, there are ways to prevent infestation in the first place. Again, your roofing professional can advise you of ways to keep your roof in tip top shape.