moss on roof

[MIKE FP]

i tried to clean moss off of a customers roof from the ground and nothing i used would even loosen it up. im guessing the only way to clean it is to go on the roof and use light pressure. it almost looks as if grass has grown on their roof. any suggestions?

 

[Russ Spence]

that is called "lichen" you will need a slightly stronger solution and some longer dwell time but it will kill the plant and it will turn loose and try adding some TSP if you are not using it to your mix