Terracotta roof tiles are typically cleaned to have the visible moss and lichen removed. Terracotta tiles are made from natural clay which is a naturally moist material. Moss and lichen is attracted to the roof tiles surface, and if left will continue to grow and 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 should be applied to all moss and lichen, prior to undertaking the roof cleaning process. I use a product called ‘Roof Ripper’ to kill the moss and lichen prior to its high pressure clean.
Once the anti-fungal treatment is applied, the roofs tile surface is high pressure cleaned using around 3000psi of straight water pressure. A turbo type nozzle should be used when using any high powered water pressure.
Removing the moss and lichen will bring the tiles natural colour to light and will help ensure the roof performs the way it was designed.
Old Terracotta roof tiles will become brittle over time and if so should not be cleaned; as the tiles may break underfoot and water will enter the roof cavity as a result, creating more issues. It is also difficult to walk on and work with brittle roof tiles, which makes it difficult to achieve any effective result.
Some Terracotta roof tiles may show evidence of “Tile Fretting”, and depending on the extent of this problem, will not benefit from any application and should not be cleaned.
Terracotta roof tiles which have glazing evident should not be sealed; painted or coated as an application such as this would have trouble with any mechanical adhesion.
Any one promoting the re-glazing/sealing/painting of terracotta roofing tiles should be avoided.
Brittle or Fretted Terracotta roof tiles should be replaced when required, as money spent on roofs with these problems would mean money wasted.
Alan’s Roof Restoration can provide the best advice for Terracotta roof restoration & replacement.