Why roofs in the west of Scotland grow so much moss
High rainfall, mild winters, plenty of shade and long damp spells are ideal conditions for moss, lichen and algae. North-facing slopes stay wet almost permanently and are usually the worst affected on any given house.
Surface texture matters too. Concrete tiles have a rougher, more porous surface than natural slate and hold growth more readily, particularly once their factory surface has weathered. Overhanging trees make everything worse by adding shade, moisture and organic debris.
Scraping versus pressure washing
Hand scraping removes growth mechanically, at a controlled pressure, with the operator able to feel and see the condition of each area of covering as they go. It's slower, and that's the point.
Pressure washing blasts moss off along with the surface of the tile, forces water sideways under laps and into the roof space, and can lift or crack slates held by tired nails. It looks impressive on a before-and-after photo and shortens the life of the roof. We don't do it.
Biocide treatment and regrowth
Once the roof is physically clear, a biocide treatment kills off remaining spores and residual growth, slowing how quickly it comes back. Treatment isn't permanent, nothing is on a shaded roof in this climate, but it substantially extends the interval between cleans.
Applying treatment without removing the bulk of the moss first is a shortcut: the dead moss stays on the roof holding water, then falls off gradually into the gutters over the following months.
Which roofs suit cleaning, and which don't
Concrete and clay tile roofs in reasonable condition clean well and benefit most. Natural slate cleans well too, provided the nails and battens are sound enough to walk the roof safely.
Where a roof is already failing, slates slipping across the slope, soft battens, perished membrane, cleaning is the wrong spend. We'll say so rather than take payment for tidying up a roof that needs replacing. In that situation the sensible route is to price the repair or replacement instead.
- Concrete interlocking tile, cleans well, benefits most
- Clay plain tile and pantile, cleans well with care
- Natural slate, cleans well where fixings are sound
- Fibre-cement slate, cleaned gently, no aggressive methods
- Failing roofs, repair or replacement first
Protecting the property while we work
Moss removal makes mess. Debris comes off the roof in volume, into gutters, onto paths and into planting. We clear gutters and downpipes as part of the job and remove the debris from the property rather than raking it into a border.
Treatment is applied with the surroundings in mind, planting, ponds, pets and drainage, rather than sprayed indiscriminately across a roof and everything below it.
Residential and commercial roof cleaning
For homeowners, roof cleaning is a mix of protection and appearance. For landlords and commercial owners it's usually about preventing the gutter blockages and consequential damp that follow years of moss shedding into the drainage.
Larger commercial roofs and multiple-property portfolios can be priced as a single fixed-price package covering cleaning, gutter clearing and treatment.
