moss on the roof

could someone please help me. i have an awful lot of moss growing on my roof. there is none on next doors. and very little on any other property's in the road. could someone explain why this happens and how do i deal with it.
many thanks. Dave.

Moss and lichen growth is common with age, especially if the roof or sections thereof are permanently shaded and damp (overhanging tree branches being a prime cause). Moss should be cleaned off, as it attracts moisture by acting as a sponge and will gradually weaken the mortar and tiles through freeze-thaw action; lichen increases levels of acidity, leading to increased erosion of mortar. Jet-cleaning will remove it, but this can, of course, force debris into cracks and, as such, the only sure way to clean the affected tiles is to remove them and hand-clean.

To prevent regrowth, the roof can either be coated with an anti-fungal preparation, or by using copper, zinc or lead strips; after rainfall, a deposit of oxide will flow onto the roof and poison the growth – look below the lead flashing on a moss-covered roof for an example of this.

The Concrete Tile Manufacturers Association has a publication called "care Maintenance and repair of concrete roof and cladding tiles" available from here.

If it were me with my roof I would very carefully pressure wash it in the right direction.
Then treat as in above post.