Moss is a familiar sight on UK roofs — particularly on north-facing slopes or properties with significant tree cover. But is it actually damaging? And if so, what should you do about it?
Does Moss Damage Roofs?
In small quantities on an otherwise healthy roof, moss is mainly an aesthetic issue. However, significant moss growth can cause real problems:
Moisture retention — Moss holds moisture against tiles, accelerating the freeze-thaw cycle that cracks and degrades tile edges over time.
Root penetration — Moss roots can penetrate into small cracks in mortar joints and tile surfaces, widening them over time.
Gutter blockage — Moss, particularly when dying or after heavy rain, breaks off and blocks gutters and downpipes.
Damp under tiles — In extreme cases, heavy moss can direct water sideways under tiles rather than down the slope.
When Should You Be Concerned?
- Moss coverage is heavy (more than a quarter of the roof surface)
- Your gutters are regularly blocking with moss
- The roof is older and already in a marginal condition
How Is Moss Removed?
Biocide treatment — A professional applies a moss-killing chemical solution. The moss dies and gradually washes away over the following weeks and months. This is our preferred approach as it avoids physical damage to tiles.
Manual scraping — Physically removing moss with brushes or scrapers. More immediate results but risks dislodging tiles and can damage fragile or older tiles if done aggressively.
High pressure washing — Not recommended. The force can damage tiles and drive water up beneath them.
Prevention
After treatment, a moss inhibitor strip can be fitted near the ridge. As rainwater flows over the strip, it releases a low concentration of biocide that inhibits regrowth for several years.
For a professional moss treatment or maintenance visit, contact Reliable Roofing Services in Coventry.
Reliable Roofing Services
Coventry's trusted roofing specialists. Expert advice from the team that gets the job done right, first time.