Moss on the roof? Not for long. No damage done.

Scottish roofs are magnets for biological growth. The damp climate, combined with atmospheric pollutants that feed algae, means most roofs develop visible moss, lichen, and algae within 8-12 years of installation. Left untreated, the growth retains moisture against the tile surface — accelerating frost damage, lifting tile edges, and eventually forcing water past the underlay. A roof that should last 50 years can need replacement in 25. The good news: a single soft wash treatment restores the roof, kills the growth at the root, and inhibits regrowth for 4-7 years.

Soft washing is fundamentally different from pressure washing. We apply a biocidal solution (typically a quaternary-ammonium or benzalkonium-based chemistry) at low pressure — around 5 bar, the same as a garden hose. The biocide soaks into the tile, kills the moss, algae, and lichen at the root structure, and breaks down over 4-12 weeks. The dead growth then washes away naturally with rain. No tiles are lifted, no granules are stripped, no underlay is compromised, and no warranty is voided. Pressure washing a roof, by contrast, strips the mineral granules from concrete tiles, cracks clay and slate, and forces water past the tile laps — a catastrophic method that we refuse to use.

We soft-wash all common Scottish roof types: concrete interlocking tiles (Redland, Marley, Sandtoft), clay pantiles and plain tiles, natural slate (Welsh, Spanish, Westmorland), and fibre-cement slates. Each material responds slightly differently — slate is non-porous and needs a longer contact time, concrete is porous and absorbs the biocide readily, clay sits in between. We assess the roof from the gutter line before quoting, identify the dominant growth (moss, lichen, algae, or a mix), and recommend the right biocide strength and contact time. For particularly steep or tall roofs, we use IRATA-certified rope access or a cherry-picker — we never walk on a roof unless absolutely necessary.