I read alot of times that people just spray on there chemicals on roofs and rinse off and bamm its new again. I want to know if you ever have to get on roof and use your surface cleaner? or does the chemicals do all the work. if so what chemicals do the trick because im here in west palm beach fl where algae roofs out number power washers. would like to know some info on chemical mixtures you can email me at www.2_BROTHERS_AND_A_PRESSURE_CLEANER@MSN.COM