Lots of people want me to bid cleaning but what they really need is a new roof and a cleaning would be a waste of money. I will give you the honest answer and what I think is going to be the best cost effective method. You know I am being honest because I do not install new roofs. However, I do offer a program for those who do not want to put on a new roof right away even though they need one. It goes like this – I will treat your roof for moss, clean your gutters and seal any leak hazards that I see. When I say treat it, I mean treatment only because I do not clean moss from old roofs. Also, I do not guarantee all the moss to completely die off from the first treatment. Usually it only takes one treatment but sometimes it could take 2. I have never seen a roof take more then 2 treatments to fully kill off the moss. Also, the roof will require regular treatments to keep it dead. The treatment will not get rid of the moss, it will still be up there looking just as ugly as ever, but it will be dead so that no further damage is being done to your roof.