Why Does Moss Keep Coming Back on My Roof?

The Direct Answer

Moss comes back on a roof because the spores never fully leave. A standard wash, pressure or otherwise, lifts the visible moss but leaves spores sitting in the gutters and in the texture of the tiles, so regrowth starts again the moment the roof stays damp for a few days in a row. The fix is steam to lift the moss without damaging the tile surface, followed by a biocide treatment that actually kills what is left behind, not just the bit you can see.

Why pressure washing makes it worse

• It strips the tile surface. Concrete tiles have a slightly rough, slightly porous face. Pressure washing can scour that surface smoother, which gives moss spores an easier place to grip next time.
• It forces water under the flashings. High pressure aimed up a slope pushes water past the laps between tiles, which is exactly where you do not want water going.
• It does nothing to the spores. Washing moss off is not the same as killing it. Without a biocide, you have cleaned the roof, not treated it.

How we actually do it

We work steam off 45-foot poles from the ground, so there is no scaffold and nobody walking on your tiles. Steam lifts the moss without stripping the tile surface the way pressure does. A biocide treatment goes on after, which holds moss off for three years minimum, less on roofs that stay shaded or face north and dry out slower. Everything that comes off the roof lands in the gutters, so clearing them is part of the same job, not an extra.

FAQ: Will it definitely never come back?

No roof treatment is permanent. The biocide holds it off for three years minimum. Shaded, north-facing roofs are at the shorter end of that because they stay damp longer.

FAQ: What does it cost?

From £750 for a two bed up to £1,500 for a five bed and above. Full detail is on the roof cleaning page.

No scaffold, no deposit. Call 07467 214446 or message us on WhatsApp.