Who thinks about cleaning their roof? No one, or at least until it's time to do so. Your roof is probably the most expensive item of your home. When it comes time to clean it you'd better be aware of the damages that caa be associated with using high water pressure for roof shingle cleaning. Though most people consider it a cleaning, we look at it as a treatment. The difference is that with a cleaning, you may have the results you were looking for as the contractor leaves your home, with your money. In this case they probably have used a "environmentally friendly" roof detergent and rinsed with "low pressure". The problem with using any type of pressure is that any type of pressure will dislodge the roofing granules. Those that did not fall off immediately are now loosened and will rinse off more and more with each rain. if you've ever cleaned out a gutter you may have noticed roofing granules inside the gutter. This is what falls off naturely with rain, so imagine what even low pressure can do. Forget about high pressure!
Black streaks on a roof is actually a type of bacteria that feeds on the limestone in the roofing shingle. They can mostly be seen on the north side of the roof with less sunlight. These stains can be removed instantly with a non-pressure treatment using sodium-hypochlorite (bleach) and water combo with a surfactant to allow the detergent to cling to the roof. With this method you can achieve a 100% kill ratio creating a longer lasting clean. This is the recommended method by both major roofing maufacture GAF and the ARMA.
When it comes to moss and other heavier growths, the results are not as immediate. After treating the moss it will turn biege and die. The ingredients of the roof detergent shock the root system, allowing it to detach from the shingle on its own. The dead moss will eventually dry out and fall off with rain. Regular moss growth can take anywhere from 4-8 weeks to be completely removed. Heavy moss can take up to 12 weeks. It's a hard sell to customers because many times they are looking for instant results possibly for home sale.
If you would like more information on NON-Pressure roof cleaning visit http://www.ThompsonRoofCleaning.com . If you would like to see how NOT to clean a roof, watch this video
http://www.dailymotion.com/video/xbk181_roof-shampooy-safety-roof-cleaning_people
