I am registered Sole Trader/Independent . Roof cleaning and Moss removal . A little bit of Moss would not be much of a problem , but if there is a lot it holds dampness and gradually soaks into the tiles ,and can damage them , especially in freezing weather . It also stops good run off from your roof and clogs your gutters and drains with debris..The best way to remove the moss/alge from your roof is with high pressure jet , if the main roof has either clay , concrete tiles ,slates , asbestos and metal roofing sheets . If you are considering having your roof cleaned , give me a call or text...AREAS I COVER : London-SW , London-W , London-NW , London-N , and 50 Miles around London .