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Is it safe to pressure wash roofs? It’s a question we are asked often.  It’s only right that home owners are concerned about potential issues when pressure washing roof tiles to remove the moss and dirt that has built up over years.

Is it safe to pressure wash roofs?

Roof tiles in the UK and Europe are generally made from concrete, slate, composite, clay and terracotta, and over time, the smooth surface of these tiles weathers and becomes more porous.  This promotes growth of moss and lichen as the spores settle into the imperfections to grow.  As a rule, the moss and lichen do not harm the tiles, although a heavy build up of moss that birds will peck at, or falls off during rain storms can cause gutter blockages and a messy path, patio or conservatory roof.  Many home owners clean off the moss to give the house a neater appearance, particularly prior to a sale.

Is it safe to pressure wash roofs?The Roof Tile Association gave it’s official view on the removal of moss and lichen from roofs back in 2016 where it addressed the main methods of cleaning:

Scraping off moss manually: “Attempts to remove moss or lichen growths by scraping them off the tile are not recommended, as it can result in broken or damaged tiles and unsightly scrape marks on the surface of the tiles, however carefully the work is carried out. Inevitably the process will have to be repeated in the future as the mosses and lichens return.

Pressure Washing: “If removal of the dead growths of moss or lichen is required this can be achieved by a low pressure (4-5 bar) jet of water, taking care not to spray against the tile laps. On no account should a high pressure water jet be used to clean off moss and lichen growths from concrete tiles. This will result in erosion of the surface thereby reducing the potential lifespan of the rooftile.

The document also warns against walking on the roof itself because roof tiles are fragile, particularly when 20 or 30 years old.

You can view the whole document on the Roof Tile Association Website Technical Documentation Library.

How does the Roof Appeal system differ from other pressure washing systems?

Our system has been developed exclusively for roof cleaning from the ground with these requirements in mind.  You can see from the Roof Cleaning Video how the water is not being used at the same pressure you would use for a patio clean.

Our system only requires enough water force to gently lift an ultra light weight (twin or triple) roof cleaning head circa 6 to 12 inches above any roof. Once the head is floating it easily removes moss, dirt and lichen as it glides. As there is no static resistance or weight acting down upon the cleaning head means our hovering roof cleaning system will not cause any new roof damage.

Can using your roof cleaning system damage a roof and it’s coatings ?

All the roofs we clean are from 10 to 60 + years old. By this time any roof coatings will have been compromised naturally by weathering and indeed this is how the moss and lichen takes hold. Regardless of this the roof will still be very sound with many more years of life.  It’s not commonly known but roof tiles do not make a roof waterproof.  They certainly help keep the worst of British weather from getting into your home, but underneath your roof tiles will be a breathable membrane that the tiles protect.

Our roof cleaning system may sometimes uncover pre existing roof damage but because of the unique way it floats over a roof will not cause anything new.

In summary, Is it safe to pressure wash roofs? With the purpose-built Roof Appeal system – yes.
Is it safe to pressure wash roofs?