Metal will clean with a light solution. I typically use 15% and lots of soap.  You will need to rinse it....every square inch!  Or time it just right and do it just before a hard rain. When the algae dies on a metal roof, its very noticeable and looks like heck! Thats the bad part of metal roofs.

-- Edited by swee****erfish on Monday 17th of May 2010 10:21:55 PM

-- Edited by swee****erfish on Tuesday 18th of May 2010 07:53:55 AM

There is supposed to be a thread here on a roof that I cleaned last year. You will have to rinse every square inch. I only used about 7% SH but strong on the simple cherry. Remember SH kills, it does NOT clean. You have to break the bond with the surface and if you are not using a pressure washer then scrubbing with a brush is in order. Follow it up with plexmaster and make the next cleaning easier.

As for time it takes 2-3 times longer.

Safety.....A dry dirty roof is slicker than a clean wet roof. Don't be afraid to walk on a wet section that has been cleaned. You will be amazed at how well you stick.