Chemical roof cleaning is a superior alternative to roof power washing, which you may already be aware of. These days, there are many roof cleaning products and solutions on the market, all claiming to be superior, and all claiming to be the safest and most reliable, but it is important to bear in mind that these are businesses who are just trying to make a buck and are going to say just about anything to sell their product.
There is only one way to clean a roof the right way, in my vast experience, and that’s with a solution based on sodium hypochlorite. Sodium hypochlorite is the active ingredient in bleach and chlorine, and is very literally the easiest, most effective way to disinfect a roof when added to a roof at the correct ratios. It is the preferred method by ARMA (the Asphalt Roofing Manufacturers Association) and GAF (the largest shingle manufacturer in North America) for cleaning roofs. Do you want to learn more? Visit roof cleaning
ARMA suggests a combination of bleach, water and TSP (which can be found in paint shops), but be careful to remove gloss at high dosages with the TSP on painted surfaces. I found that, since the bleach is the primary cleaning agent, the TSP is helpful but not necessary. Furthermore, every roof cleaning professional using this method has its own “secret” additives that they add to this mix to give it just the right cleaning power for their environment, but a final liquid solution that is around 3-4 percent sodium hypochlorite is the common denominator. So you will need to have equal parts of bleach and water to get you down to 3 percent if your typical household bleach is around 6 percent.
This is by far the easiest and most effective way to clean a roof, but the catch is that anywhere from 30 to 60 gallons of total mix would be needed for an average one-story ranch house. That means you’d need a standard 6 percent household bleach of around 15-30 gallons. Usually, in a large poly tank on their truck or trailer, the pros will have the whole mix and will use a battery-powered pump to deliver the solution to the roof surface through a long polybraided hose. Typically, at the end of the hose, they would have a bleach resistant tip that disperses a gentle spray uniformly across the surface of the roof. Before rinsing the surface with water from the garden hose, they’ll leave the solution on the surface and let it do its thing for several minutes. So there should be no need for power washers or scrubbing (the only exception could be for thick moss accumulations). If you do this yourself, during the application, you may also want to keep the entire perimeter of the home rinsed down very well (preferably by a second person) because if not properly diluted, sodium hypochlorite may have a detrimental impact on landscaping. Be particularly conscious of areas in which downspouts empty into grass or other greenery.