Problem

Damp patch upstairs: is the roof growth causing it?

Damp appearing on an upstairs ceiling or a chimney breast sends most people straight to the roof, and often to the moss on it, because that is the visible thing. Sometimes the moss is genuinely involved. Frequently it is not.

Spending money in the wrong order is the expensive mistake here, so this page is about narrowing down the source before anyone quotes you for anything.

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a roof slope part cleaned, showing the untouched moss alongside — problem: damp patch upstairs: is the roof growth causing it?

Where the patch is tells you a lot

Close to an outside wall at the top of the room: usually eaves, gutter overflow or a blocked downpipe rather than the slope itself.
Around a chimney breast: flashing, cracked cement fillets or failed flaunching are far more likely than surface growth.
In the middle of a ceiling under a valley: debris in the valley holding water and forcing it sideways under the tiles.
Only after wind-driven rain from one direction: an opening on that elevation, often a slipped tile or a gap at the verge.
Constant regardless of weather: think condensation, plumbing or ventilation before roof covering.

How moss genuinely contributes

Growth does not usually make a roof leak by itself. What it does is hold water on the covering for longer, wedge under laps as it travels downhill, and fill gutters and valleys so water is diverted somewhere it was never meant to go.

It also hides the real culprit. A slipped tile or a cracked fillet under a thick blanket of moss is invisible until someone clears the slope and looks properly, which is why so many defects are found during cleaning rather than before it.

The order that saves money

Check and clear the drainage first, because blocked gutters and downpipes cause more damp than most people expect and cost the least to put right. Then clear the roof so the covering can actually be inspected.

Once the slope is clear we photograph anything we find, and where the answer is chimney repointing, pot work or ridge re-bedding that is work our own team carries out. Where the answer is structural roofing, we say so plainly instead of stretching what we do.

What we will not claim

We are a cleaning and roof-care company and we do not diagnose damp indoors. What we can do is rule the outside in or out with photographs of the actual condition, which is usually the missing piece.

Surveys and quotes are free and carry no obligation, so getting an honest look at the roof before committing to any work costs you nothing.

Our own photographs

Images from Sky Scrapers Ltd work showing the methods described on this page.

a roof slope part cleaned, showing the untouched moss alongside, relevant to damp patch upstairs: is the roof growth causing it?

a before-and-after comparison of a tiled roof cleaned by hand, relevant to damp patch upstairs: is the roof growth causing it?

a cleaned pitched roof on a detached house, relevant to damp patch upstairs: is the roof growth causing it?

Where this applies locally

Towns where this comes up most often on our patch:

Questions we get asked

Can moss on its own cause a leak?

Rarely on its own. It holds moisture, blocks drainage and hides defects, and it is usually one of those three that produces the damp rather than the growth itself.

Should I clean the roof before calling anyone about the damp?

Clearing lets the covering be inspected properly, which is often what identifies the cause. Start with gutters and downpipes if they are visibly blocked.

Do you find the leak as part of a clean?

We photograph what we see and report it. We do not carry out internal damp diagnosis, and we will tell you when a roofer is the right next call.

Is a free survey available?

Yes. Quotes and surveys are free with no obligation.

Get the outside ruled in or out

Send photos of the damp patch and the roof above it, and we will tell you honestly what we can and cannot see.