Maybe Trader will enlighten us. I've heard it mentioned as a possible solution for discoloration, but I never really thought about it for composition materials, so I researched it a bit. As one might think, high pressure power washing dislodges granules, and some chemicals soften and/or dry the asphalt base. Still, some power wash companies recommend it. A lot of companies tout their low pressure power wash methods, and some chemical companies will include information on how to convert high pressure washers to appropriate levels. I also discovered something called Spray and Forget it that is suppose to kill algae and fungus growth over a period of time and deposit a residue that will retard and prevent future growth. For badly affected roofs, there can be an initial application of mild bleach water (to be rinsed thoroughly after a very short stand time). This product uses a garden sprayer rather than a power wash...but includes instructions to be used with a powerwash option. I have a light colored 3-tab under two huge pecan trees. I have some mild discoloration which I thought I'd have to live with as natural patina. Now, I have something to try that might work without taking years of granules from my roof. I hope Trader will come back and explain the coverage aspect to this whole subject. Could be a wind storm deposited some large branches that left fungus colonies (are fungi social?) as the only sudden physical damage or something. Maybe someone has experience with the spray and leave type chemicals that might save me a bad experience. RandyC! |