If you were to just clean your roof with water, the moss and lichen would return in 12 months time. However, after the wash we apply an anti-fungal treatment to the entire roof, which actually kills the organic spores and stops them from re-growing. In addition to this, we also apply two coats of 100% acrylic, fungicidal quality, waterproof coating. This helps to seal the porous surface of the tiles and prevents moss, lichen and algae from both growing back on the surface of the roof in the future.