How long does a roof clean last?

“How long will it last?” is one of the first things James gets asked on a roof-cleaning call, and the honest answer is that nobody can give a fixed figure without seeing the roof. A roof clean is not a coat of paint with a printed shelf life. How long it stays moss-free depends far more on the roof it went onto than on the treatment itself.

Why there isn't a fixed answer

It depends what actually happened during the clean. Scraping or jetting moss off the surface removes what you can see but leaves the roots in the tile, and that grows back fast — often within a season. Whales' roof cleaning combines manual moss scraping with a hot-water, low-pressure clean and a BAC 50 biocide treatment, and the biocide is left to work into the moss rather than simply rinsed straight off. That is what gives the result its staying power. James checks the tile type and condition before deciding the method, because what is safe and effective on clay is not always right for ageing concrete.

What brings it back faster

• North and east-facing pitches, and anything under mature trees, stay damp for longer after rain and in shade for longer through the day. Moss needs both, so these pitches always re-green first — our guide on why moss ends up in your gutters covers the same pattern.
• Older concrete tiles are more porous than newer concrete, clay or slate, and give spores more to grip onto.
• A shallow pitch holds water and windblown debris longer than a steep one.
• Gutters that silt back up hold moss-laden debris hard against the tile edge, which is one reason our roof-cleaning package always includes a gutter clearance rather than treating the tiles in isolation.

What actually to expect

Rather than quote a blanket number, James looks at tile type, orientation, shade and how established the moss already is before he confirms the price and talks through what to expect for that specific roof. A south-facing roof in modern low-porosity tile with nothing overhanging it can go several years without needing another look. A shaded, older, north-facing roof under a conifer can show a thin green tinge on the worst corner within a year or two — that is not the treatment failing, it just means that one pitch is a harder environment than the rest of the roof, and a light spot-retreat there costs a fraction of the original job.

What's included, so the whole outside matches

Roof cleaning starts from £11/m² and the package bundles in a window clean, gutter clearance and house wash, so the roofline, the glass and the walls beneath it all come back to the same standard in one visit rather than three separate call-outs. If the gutters are what brought you here in the first place, our guide on what moss removal actually costs breaks the roof and driveway figures down side by side.