7 Signs Your South London Roof Is Due a Clean

Most people never look at their own roof. It sits up there out of sight until something goes wrong, and by then the cheap fix has often become an expensive one. A few minutes looking up from your garden or the pavement can save you a lot.

You do not need to climb anywhere to spot the warning signs. A clear day and a decent pair of eyes, or a phone camera zoomed in, will tell you most of what you need to know. Here are seven signs that a South London roof is overdue a clean.

The quick answer: Thick moss, dark streaks, grit in the gutters, plants in the gutter line, water spilling over in rain, damp patches inside, and a roof that looks darker than your neighbours' are all signs it is time. Catch them early and a soft wash sorts it before any of them turn into a repair.

1. Thick moss you can see from the street

The obvious one. If you can see green cushions of moss on your tiles from the pavement, there is a lot more up there than it looks. Moss reads as small from the ground and turns out to be inches deep close up.

Thin patches are not urgent. Thick, spreading moss holds water against the tiles and needs dealing with before it blocks the gutters and lifts the laps.

2. Dark green or black streaks running down the slope

Those streaks are algae, not dirt, and no amount of rain will wash them off. They start as a grey shadow and darken into bold black or green lines running down the tiles from the ridge.

On the pale render and light tiles common across South London's interwar suburbs, algae streaks stand out a mile and drag down the whole look of the house. They also signal a surface staying damp enough to feed constant growth.

3. Grit and tile fragments in the gutters

Next time you are clearing the gutters, look at what comes out. A few leaves are normal. A sludge of gritty granules and small tile fragments is your roof telling you its surface is breaking down.

This is common on older clay and on concrete tiles that have lost their coating. The grit is the tile surface washing away, and once that starts the tiles grow moss faster and need attention.

4. Plants growing in the gutter line

Grass, weeds, or the odd tree seedling sprouting from your gutter is not a quirky bit of greenery. It means enough leaf litter and soil have built up to support a plant, which means the gutter has been blocked for a while.

Where there are plants, water is not draining, and where water is not draining it is spilling somewhere it should not. This one is worth acting on quickly.

5. Water pouring over the gutter in rain

Wait for the next proper downpour and watch your gutters. Water should run quietly to the downpipes. If it is cascading over the front edge like a small waterfall, the gutter is blocked and the overflow is hitting your walls.

Every time that happens, water soaks into the brickwork. Do it through a wet South London winter and you are well on the way to damp inside.

6. Damp patches or a musty smell in upstairs rooms

Sometimes the first sign shows up indoors. A yellowing patch on a bedroom ceiling, a corner that smells musty, paint starting to bubble near the top of a wall, all can point to water getting in from above.

It does not always mean a dramatic leak. Often it is a slow one from a blocked valley or a slipped tile, the kind that a roof clean and inspection would have caught long before it reached your ceiling.

7. Your roof looks darker than the rest of the street

Stand back and compare your roof with your neighbours'. If yours looks noticeably darker, greener, or patchier, it is carrying more growth and grime than theirs, and it is due a clean.

This is an easy check on South London's consistent interwar streets, where the houses were built the same and the roofs started identical. If yours stands out, it is not standing out for a good reason.

What happens if you keep putting it off:

• Blocked gutters overflow: water runs down the walls and soaks in.
• Moss lifts the tiles: growth forces under the laps and lets water past.
• Damp reaches the inside: patches, blown plaster, and that musty smell.
• Small repairs become big ones: a clean turns into a re-bed or a re-roof.

Frequently Asked Questions

How often should a South London roof be cleaned?
Every few years for the moss, depending on shade and tree cover, with a yearly gutter clear. Roofs under trees need it more often than open ones.

Are black streaks actually a problem or just cosmetic?
Mostly cosmetic at first, but they show a surface staying damp enough to feed algae, which often comes with moss. Clearing them improves the look and the roof's condition.

Can I check my roof myself without going up?
Yes. From the garden or pavement with a zoomed-in phone photo you can spot moss, streaks, slipped tiles, and blocked gutters. Leave the actual climbing to someone with the right kit.

Is grit in the gutters really a warning sign?
It can be. On older tiles it means the surface is breaking down, which speeds up moss growth. Worth keeping an eye on and cleaning before it gets worse.

My roof looks fine but my neighbour just had theirs done. Should I bother?
If yours genuinely looks clean and clear, there is no rush. If it looks darker or greener than theirs, it is probably carrying growth you cannot see well from the ground.

Spotted a few of these on your roof?
Ben's Roof Cleaning checks and cleans roofs across South London, with over 15 years of experience. Get in touch or call 020 3435 9666 for a free, no-obligation quote.

Catching it before it costs you

None of these signs mean disaster on their own. What they mean is that your roof is asking for a bit of attention before small problems grow into expensive ones. A quick look up every few months, and a clean when the signs start stacking up, keeps a South London roof sound and off the list of things you worry about.