The short answer
Clean them when the tiles are intact and the trouble is only growth or staining. Replace them when they are cracked, crumbling or flaking across a slope, or when the covering is past its published range. Age alone does not decide it: HomeBuilding gives clay 60 to 80 years and plain concrete 40 to 50, so condition on inspection settles the question.
Age against typical lifespan
Start with the material and a rough age. HomeBuilding & Renovating (Sep 2025) lists clay tiles at "60-80 years", plain concrete and Double Roman at "40-50 years" and fibre cement at "30-40 years". Marley's expectation for its concrete tiles is around 60 years, with a warning that this does not promise anything for a given roof. The BRE minimum of 60 years applies to clay only.
These are typical ranges. They give a rough position on the road. A 30-year-old concrete tile roof is well within its range, and cleaning is a sensible spend. A 55-year-old one is past the shorter published range, so the first question is whether cleaning is worth doing in the first place.
Age is only a prompt. A well-made roof in a sheltered spot may outlast the table, and a poorly fixed one on a damp site may fail early. The lifespan figure says nothing about the individual roof.
When the age is unknown, a house survey, an old invoice or a neighbour's matching roof can offer a clue. Our page on how long roof tiles last sets out the published figures for each material.
What the inspection finds
Condition matters more than age. A close look at the tiles settles the question, and the signs fall into two groups.
Signs that cleaning will be worthwhile include the following.
- Tiles whose surface is intact under the growth.
- Moss and streaks only, with no cracks or flaking.
- Few slipped or broken tiles, and those easily replaced.
- Sound underlay and battens, seen from the loft.
Signs that replacement is the better route include these.
- Tiles that flake, delaminate or crumble when touched.
- Cracked or porous tiles across much of a slope.
- Nails that have rusted, with tiles slipping repeatedly.
- Daylight, damp patches or rotten battens visible in the loft.
A roof can sit between the two. Sound tiles with one patch of poor ones can be cleaned, with the poor ones replaced during the same visit. Our page on repairs after moss removal explains why that is common.
Cleaning does not restore a worn tile. It removes growth, and it cannot cure cracks or porosity. If cleaning only exposes a failing covering, the money is better spent on the covering itself, ideally on a repair that reaches the cause of the failure instead of another round of surface treatment.
Cost drivers
What cleaning costs is settled by a survey, because the area of the roof, the access, the pitch and the weight of growth all count. Scaffolding or a tower, where the roof is high or awkward, can add more than the cleaning itself. Check whether any quote includes it, and VAT.
Replacement costs a great deal more, and the national guides disagree about how much. Which? (Nov 2025) gives a range of £7,000 to £21,000, ex VAT, to re-cover an entire average three-bedroom house. HomeBuilding (Sep 2025) puts a three-bedroom semi of 65 m² in plain concrete tiles at between £10,000 and £15,000, including labour, scaffolding and insulation. They are national guide figures, not our prices.
The gap between the two choices is why the decision should rest on evidence. Spending on a clean that buys two years before a re-roof is poor value, and re-roofing a sound roof is poorer still. Either mistake costs real money.
A middle path is a partial replacement. Failed tiles, ridge or verge sections are replaced and the rest cleaned, which keeps the cost proportionate. We would recommend that where the evidence supports it.
Our roof tile replacement cost page gives the figures for small repairs.
Making the decision
The sensible order is to inspect first and decide second, and to keep the two apart so that nobody is selling you the answer before the evidence is in. We measure and photograph the roof from the slope and the loft, identify the tile, and tell you what condition it is in. You see the pictures and hear the reasoning.
Then the choices are put plainly: clean now, clean and repair, or plan a re-cover. We say which we think the evidence supports and why. If the roof is sound, we would not push a re-roof. If it is failing, we would not clean it for the sake of it.
Mind how the cleaning is done: Marley advises against high-powered jet washes for the damage they do to tile surfaces, so a gentler method is the right basis for any quote. Treatments must be approved products used to the label.
The written quote is one total. It states whether repairs are included, which avoids a disagreement later.
If you are thinking of selling, the same logic applies, and our page on cleaning the roof before selling explains it. The roof cleaning and moss removal hub covers the full service.
