Roofs decline slowly enough that most homeowners don't notice until something obvious happens — a leak, a fallen tile, a stain on the ceiling. By that point, you're paying for a repair as well as a clean. The signs below are what we look for when we drive past a property. If you can spot more than two of them on your own roof, it's time to book a clean.
1. Visible green or black streaks
Vertical green streaks are usually moss or algae growing in the porous surface of concrete tiles. Black streaks are typically gloeocapsa magma — an algae that feeds on the limestone in the tile coating. Both are easy to remove with soft washing. Both come back fast without biocide treatment.
2. Clumps of moss in the gutter
If you can see moss in the gutter from the ground, the roof above is shedding it. Heavy moss adds weight to the roof, holds water against the tile surface (accelerating wear), and lifts tiles slightly when it grows under the laps. See our companion guide on when to clean your gutters.
3. Dark patches on north-facing slopes
North-facing pitches stay wetter for longer and grow moss faster. If your north-facing slope looks noticeably darker than the south-facing one, that's moss and algae — not a shadow.
4. Plants growing on the roof
Once moss is established, seeds blow in and find a foothold. Small grasses, weeds, and even tiny saplings on a roof are not a quirky garden feature — they're a sign the roof has held water and organic matter long enough for things to grow.
5. Loose granules in the gutter or at the foot of downpipes
Concrete tiles have a granular coating that protects the cement underneath. If you find a layer of grit at the bottom of your downpipe, the coating is breaking down. Cleaning soon will protect what's left.
6. The roof looks much darker than your neighbours'
If your roof is noticeably grimier than the houses either side of you, it's not your imagination. Cleaning brings the colour back to close to the original tile finish — see our gallery for before/after examples.
7. The last clean was more than 3–5 years ago
Even a roof that looks fine should be cleaned every 3–5 years. Moss is much easier (and cheaper) to remove early. Letting it establish doubles the price and the time.
Get a free roof inspection
We'll come and look at your roof at no cost and tell you honestly whether it needs cleaning yet. Call 07841 595419 or request a free quote online.
We cover Manchester, Cheshire, Chester, the Wirral, Liverpool, North Wales and surrounding areas. See our main roof cleaning page for full details.
