We use a rotary jet of just water because normal jetting will cause more harm than good
And with our machines it gets all the moss out of the tiles including acid
Rain discolouring .be careful climbing around on roofs !. Mark Newman
Depending on the type of materials on your roof, slates or tiled, moss can have a bad effect on the condition of these. I would have someone inspect your roof BRFORE you try to clean it or you may cause more damage before you solve the problem. Saying this however, it is a relatively easy procedure that can be scraped or power washed. U can use a chemical to remove also but usually with a bit of scrubbing it will come off.
GM Home Improvements.
We also carry out this kind of work, sometimes steam cleaning can be a problem and affect the surface of the roof covering, we often use a more traditional method of scrubbing by hand with a moss killing liquid.
Chris Miller (The Roofing Co)