Heavy build-up of moss on flat roof

[taz777]

I wasn't sure of which section to ask this question so I apologise in advance if it's in the wrong section.

The house I want to buy has a heavy build-up of moss on the extension and garage flat roofs.

What's the best way to clear this whilst not damaging the roof itself?

 

[LooPrEvil]

Try not to walk on the roofs, that how most damage can be done. Try a hose pipe or pressure washer (but be careful with the latter!), and a stiff brush. I am assuming these roofs do not have chippings on them.