Moss is a problem that lots of houses suffer with. Not only does it look dirty/untidy on the roof, but it also creates more problems lower down the house.
The birds pick at it and throw it on the floor.
It rolls into the gutters, blocks them and then causes water to overflow down the walls causing problems to the brickwork.
Clean as a Whistle Dorset works on the roof to clear the moss by hand before spraying the cleared roof with solution to help slow down the re-growth.