Everything green on a building is there because the conditions suit it, and cleaning removes the growth without changing the conditions. That is why one house is spotless four years after a clean and another is green again in eighteen months. Devon's climate does the rest: mild, wet and rarely cold enough for long enough to kill anything off. You cannot make a property permanently moss-proof, and you should be sceptical of anyone claiming otherwise, but you can change enough of the variables to double or treble how long a clean lasts.
Moisture is the whole story
Algae, moss and lichen all need water and they all need it to stay put. Any surface that stays damp for long periods will grow something. That is why the north elevation goes first, why the wall under a leaking gutter is worst, and why the strip of patio in permanent shadow is always the slipperiest part. Every prevention measure that works is a variation on the same theme: help the surface dry out faster.
This guide sits under our Wall Cleaning & Softwash work, covering 20-mile radius of Plymouth.
Fix the gutters and downpipes first
Nothing regreens a wall faster than water running down it. A gutter that overflows in every heavy shower keeps a vertical strip of render permanently damp, and no treatment survives that. Clearing gutters annually, fixing a dropped joint and redirecting a downpipe that splashes onto brickwork will often do more for the appearance of a house than another clean.
Cut back what is holding the damp in
Overhanging branches drip onto roofs and walls for hours after rain has stopped, drop leaf litter into gutters and block the sun and wind that would otherwise dry the surface. Shrubs planted tight against a wall do the same at ground level. Trimming back to leave an air gap around the building is unglamorous and genuinely effective.
Look at where the water goes at ground level
A path that falls towards the house, a flowerbed built up above the damp course, or a soakaway that no longer soaks away all keep the wall base wet. That lower metre of render is nearly always the first to go green again. Correcting the levels or the drainage does more than repeated cleaning of the same strip.
Maintenance treatments beat rescue cleans
A light biocidal application every couple of years, applied before growth is visible, keeps a surface in the state it was left in after the deep clean. It is quicker and less involved than a full clean, and it means you never get back to the point of needing heavy mechanical work. This is the single most reliable way to keep a property looking maintained.
Understand which surfaces will always be worst
North-facing walls, shaded patios, tree-lined driveways, roof pitches that get no afternoon sun and anything within splash range of a downpipe are permanent hotspots. Rather than treating the whole property to the same schedule, it is often better to have the hotspots refreshed more often and leave the sunny elevations longer.
What does not work
Household bleach on paving is a temporary result that damages planting and does nothing to the roots. Scraping moss off a roof without treatment leaves the holdfasts to regrow. Copper or zinc strips have some effect immediately below them on a roof and very little further down. Sealing a surface that is still biologically active seals the problem in.
A realistic maintenance rhythm
For most houses in and around Plymouth: gutters annually, windows on a regular round, a light treatment on shaded walls and the patio every year or two, hard landscaping cleaned every one to two years, and a full roof clean only every several years if the interim work is being done. That rhythm costs less over a decade than three rescue jobs.
Questions we get on this
- How long should a clean last before moss returns?
- It varies with shade, trees and drainage. Sunny, open elevations can look good for years; shaded ones under trees can green up within a couple of seasons without maintenance.
- Do copper or zinc strips stop roof moss?
- They have some effect on the courses immediately below them and much less further down the pitch. They are not a substitute for treatment.
- Is a maintenance treatment cheaper than re-cleaning?
- Generally yes, because it is a shorter visit with no heavy mechanical work, and it stops the surface reaching rescue condition.
- Will bleach from the supermarket do the same job?
- No. It gives a short-lived surface result, does not kill growth at root level and risks damaging planting and joints.
Related reading
- Granite, limestone and Devon stone walls
- uPVC cladding, fascias and soffits
- Indian sandstone patios: cleaning without blotching
- Porcelain paving: low maintenance, not no maintenance