Moss is not automatically a crisis, but it changes how a roof behaves. It holds water against the covering, it breaks off and washes into gutters and valleys, and on a shallow pitch it can dam water back under the laps. The associated problem, gutters full of moss and leaf litter, quietly does more damage to walls and fascias than most single roof faults.
Why pressure washing is usually the wrong answer
A jet wash strips moss quickly and takes the weathered surface of concrete tiles with it, leaving them more porous than before. It also drives water up under laps and into the roof space, and on slate it can loosen fixings. Roofs that have been jet washed frequently look worse three years later than roofs that were left alone.
Careful manual removal, working down the slope, is slower and far kinder to the covering. Where growth keeps returning, a copper or zinc strip near the ridge reduces it over time without attacking the tiles.
What debris actually blocks
The real damage is where water is meant to be channelled and cannot be.
- Valleys silting up and overtopping into the roof space
- Gutters overflowing behind the fascia and rotting the timber
- Flat roof outlets choked by moss washed down from a pitched slope above
- Hopper heads and downpipes blocking at bends
- Lead back gutters behind chimneys filling with grit
Gutters are a building problem, not a roof problem
An overflowing gutter soaks the wall below it repeatedly. On solid-wall Norfolk properties that shows up as internal damp on the ground floor, spalled brick or blown render, and rotten fascia and soffit, costs that dwarf the price of clearing the gutter. If you are going to do one piece of roof maintenance a year, this is the one.
What we do on a clean-and-check visit
We clear gutters, valleys and outlets, remove moss by hand where it is causing a problem, flush the downpipes, and look at the covering, flashings and ridge line while we have access. You get told what we found, including the things that are fine. Where something needs attention it goes in a written quote, we do not invent work while we are on the roof.
Common questions
Does moss actually damage a roof?
Indirectly. It holds moisture against the covering, accelerates frost damage on porous tiles, and the debris it sheds blocks the drainage details that matter. On a well-drained roof with sound tiles, light moss on a north slope is largely cosmetic.
How often should gutters be cleared?
Once a year for most properties, twice where there are trees close by, late autumn after leaf fall is the important one.
Do moss killers work?
Biocide treatments slow regrowth after manual removal. They are not a substitute for clearing the material that is already blocking valleys and gutters, and run-off needs thinking about near planting and ponds.
Can you clear gutters on a two-storey house?
Yes, with appropriate access. We will confirm what access the property needs in the quote rather than turning up and adding a charge.