Yes, bump up your surfactant. Tile Roofs always require more. Also you may want to add some sodium hydroxide to your mix. This will help boost up the PH level in your SH and also help loosen and remove that lichen on the Tiles when it rains...
-- Edited by Roof Cleaning Palm Harbor FL 727 543 3276 on Monday 17th of August 2009 12:19:13 PM
How did this one turn out? That looks like heavy duty tile. If its not too steep I would climb that like a billy goat mate. We had some similar stuff on some concrete caps, quite the pain in the azz. Once we took the bulk of the organic matter off, there was still a stain around the perimeter of every blasted little blotch. Had to let it dry and then sock it again. Came out ok, but not like new. Good luck Down Under with these!
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