Guide · DY Exterior Cleaning Ltd
How to remove moss from your roof safely (and what NOT to do)
Roof moss should be removed using soft-wash biocide treatment, never high-pressure water. Hand-scrape the heaviest growth, apply a sodium hypochlorite-based wash at low pressure, and the spores die at root. The roof returns to original colour over the following weeks.
Why removing moss matters
Moss holds water against your tiles. In winter that water freezes, expands, and cracks the surface coating. Over years that shortens the life of the roof, typically by 5,10 years on concrete tiles.
The right method: soft wash
Soft wash means low-pressure application of a controlled biocide (usually sodium hypochlorite based). The chemical kills the moss and the spores. Dead moss then washes off over weeks of rain, restoring tile colour without damaging the surface.
Why you should NEVER pressure-wash a roof
High-pressure water strips the protective coating from concrete tiles, forces water under the laps where it can rot battens, dislodges mortar from ridge tiles, and voids most roof warranties. Any company that quotes for jet-washing a roof should be ruled out immediately.
DIY vs. professional
DIY is realistic for ground-floor extensions and outbuildings, wear PPE, work from a tower scaffold, and use a domestic biocide spray. Main roofs need professional kit (high-volume biocide pumps, reach lances, safe roof access) and proper insurance. Don't climb a two-storey roof on a ladder.