This process involves the high pressure cleaning of Terracotta or Concrete roof tiles.
Concrete Roof Tiles are normally only cleaned where the intention is to re-seal & re-paint/coat the roof tiles surface after.
Terracotta Roof Tiles are normally cleaned to have the moss & lichen removed. Terracotta tiles are made from natural clay which is a naturally a moist material. Moss & Lichen is attracted to the roof tiles surface & if left will grow & most likely restrict the flow of rain water over the tiles surface into the roofs gutters.
An application of an environmentally friendly anti-fungal solution is applied to all moss & lichen prior to undertaking the roof cleaning process.