Heavy moss growth
A film of moss on a north-facing slope is normal in Scotland and largely cosmetic. Thick growth is a different matter: it holds water against the tile surface, blocks drainage paths and washes into gutters where it forms a dam.
What it looks like from above
- Deep green cushions along tile laps and at the bottom of the slope
- Moss packed into valleys and behind ridge and hip lines
- Fragments visible in the gutter channel and at the downpipe outlet
- Uneven drying patterns on the slope after rain
What happens if it's left
- Constant moisture accelerates freeze-thaw damage to the tile surface
- Valleys and gutters block, so water backs up under the tiles
- Aggressive scraping or pressure washing does more damage than the moss did
How it's normally fixed
Careful manual removal and a gutter clear-out, not a pressure washer — high-pressure water strips the tile surface and forces water under the laps. Photographs help you judge whether it needs doing at all this year.
Common questions
Should moss be removed from a roof?
Only when it is thick enough to block drainage or sit in valleys and gutters. Light growth on a north-facing slope is not doing measurable harm.
Is pressure washing a roof a good idea?
Generally no. It erodes the surface of concrete tiles and drives water under the laps. Manual removal is slower and much safer for the roof.
Think you've got this on your roof?
We photograph every elevation, circle each defect and grade it by severity — £99 residential, £149 commercial, report within 24 hours.