Is moss damaging my roof?
Moss itself rarely destroys a sound covering. The problems it causes are indirect: it holds moisture against surfaces, it breaks away and blocks gutters and valleys, and it can hold water against mortar joints where frost then does the damage. Heavy growth is also a sign of a slope that stays damp, which is worth understanding in its own right.
What moss does and does not do
On a slope in good condition, moss is mainly a maintenance issue: it displaces water at laps and it ends up in the gutter. Where mortar bedding, porous coverings or defective details are already present, retained moisture accelerates deterioration.
Aggressive removal can do more harm than the moss. Pressure washing has stripped the surface off tiles and driven water under coverings on roofs we are called to afterwards, so method matters.
What evidence should you look for?
These are indications, not conclusions. Each one narrows where to look; only an inspection confirms a cause.
Heavy growth on one slope only.
That slope may stay damp through shading or poor drainage.
Areas that may need investigating
- overhanging trees
- gutter and valley flow
- surface condition beneath
Gutters repeatedly blocked with moss.
Water may be overflowing onto walls rather than draining away.
Areas that may need investigating
- gutter falls and outlets
- wall staining below
Urgency: Monitor
Moss growth is usually a maintenance matter that can be planned, rather than a defect requiring an urgent response.
Repair or replace?
Maintenance may be enough when
- Growth on a sound covering with clear gutters as the main concern
Further investigation is the right next step when
- Surface of the covering appears to be breaking down beneath the growth
How we can help
- Moss RemovalMoss removal is the targeted stripping of moss growth from a roof covering and its drainage using manual scraping and low-pressure soft washing, followed by an optional biocide treatment to slow regrowth. It is carried out to restore drainage and prevent water being held against the covering.
- Roof CleaningRoof cleaning removes moss, algae, lichen and debris from a roof covering and its drainage. Done correctly it protects the covering and restores drainage; done with a high-pressure lance it strips surface material, drives water under the units and can take years off the roof's life.
- Gutter CleaningGutter cleaning clears leaves, moss and silt from gutters, hoppers, outlets and downpipes so rainwater leaves the building rather than overflowing down the wall. It is the cheapest preventative maintenance available and prevents damp, pointing erosion and fascia rot.
Related questions
What should you do next?
Deal with gutters and valleys first, and have the covering looked at before any cleaning so the method suits the roof rather than damaging it.