Today we removed the moss from a roof in Kinson, Bournemouth. The roof was sound structurally but it had very thick moss all over it. The moss absorbs water like a sponge and can eventually lead to water getting under the tiles, as well as falling down all over the grass and infecting that.
It was a hard couple of days scrubbing but the roof looked amazing when we had finished. After the moss was gone we treated the roof with bleach to kill the spores, then waterproofed the tiles before applying copper tape along the ridge tiles. The copper salts wash down the roof when it rains and prevent further moss growth.