[Scott Dean]

I've picked up a garage roof clean (double garage with pitched roof about 20 years old) that needs the moss and general build up of crud taken off. As I currently don't own a jet wash or lance I'm going to hire them from my local tool shop but I was mainly wondering what biocide (if that's the right word) would I need to treat it with to stop the fungus and/or moss growing back??

I'm cleaning it this coming Friday so any suggestions would be great..,