There is no shortage of ways to get moss off a roof, and most of them work for a while. The differences lie in what they do to the tile, how long the result lasts and what they cost. A method that clears the roof in an afternoon may leave it greener than before within a season, while one that looks unimpressive on day one can leave a clean surface for much longer. This page sets the main methods side by side so you can judge a quote, and see why we favour some over others.
What moss does, and why method matters
Moss is a plant that anchors with fine strands in the pores and laps of a tile, and holds water like a sponge. The aim of removal is to take it off without harming the tile and to make it harder for the moss to return. Those two aims pull against each other. Force removes moss quickly and roughens the surface, which helps the next lot take hold. Chemistry is gentler on the surface but slower. Most good cleans use a little of both, in the right order. For a view of whether moss needs removal at all, see our answer on whether moss on roof tiles is a problem.
Method 1: scraping and hand removal
A cleaner works across the roof with a scraper, a stiff brush or a gloved hand, lifting the moss out of the laps and off the tile faces. Thick moss comes off in mats. It is the oldest method and the simplest.
What it does well
It clears the bulk of the growth where it matters most, in the laps, at the bottom edge and in valleys, and it is the right first step when moss is thick. It uses no water and little chemical, so run-off is small.
Where it goes wrong
Scraping on its own leaves roots and spores, so regrowth is quick. A hard scraper or wire brush can scratch the surface of a tile, lift the face of concrete or damage the edge of a slate. The cleaner has to be on the roof, which brings the risks covered in our guide to roof cleaning safety. It is slow, so the labour charge is higher for a large roof.
Method 2: pressure washing
A pressure washer sends a narrow jet of water at the roof, blasting moss and dirt off. It is fast and visibly effective, and it is the method most people picture.
What it does well
Speed and appearance. A roof can look dramatically better in hours, and it costs less to hire than the alternatives.
Where it goes wrong
Pretty much everywhere else. The jet can strip the surface layer from concrete tiles, scour handmade clay, chip slate, force water under the laps and onto the felt, blow out mortar at the ridge and verge, and loosen nails. Roots remain in the tile, and the roughened surface regrows faster. Run-off is large. We have set out the damage in our guide to high-pressure washing, and it is why we do not recommend it on pitched roofs. Published UK cost guides report a pressure wash at £553 for a small roof, £638 for an average one and £723 for a large one, so the saving against other methods is real but not large.
Method 3: soft washing
Soft washing applies a cleaning solution at low pressure, then rinses gently or lets the weather do it. The pressure is no higher than a garden hose. The cleaning is done by the chemistry, not the force. Our answer on what soft washing is describes it in more detail.
What it does well
It is gentler on tiles and mortar and works across the whole surface, including the laps. It suits delicate coverings and is used widely on algae and black streaks.
Where it goes wrong
It does not remove thick moss on its own, which still needs hand clearing first. The result develops over days or weeks. The solution and the run-off need managing, as set out in roof cleaning, run-off and wildlife.
Method 4: biocide treatment
A biocide is applied to kill the growth, then left to work. Moss turns brown, dies and falls away over weeks. It is often combined with hand clearing and soft washing in one visit. We explain the details in roof biocide treatments.
What it does well
It kills at the root, spares the tile, and slows regrowth more than any force-based method. It reaches places a person cannot, such as shaded laps. It suits almost every roof covering when used as the label directs.
Where it goes wrong
It is not instant, and some owners are disappointed on day one. It depends on weather, because heavy rain too soon can dilute the effect. Wrong product, wrong dilution or poor coverage reduces the result. It needs care around plants, ponds, pets and water butts.
Method 5: hand removal plus biocide
This is the combination most roofers prefer. Thick moss is lifted by hand, the roof is treated with a biocide at low pressure, and the remaining growth is left to die back and weather off. It costs a little more than a pressure wash. For hand removal with biocide, UK cost guides give £748 (small), £863 (average) and £978 (large). The price you are given comes after the visit, and the reasoning behind it is set out on our roof cleaning costs page.
Method 6: zinc and copper strips
Strips of zinc or copper fixed below the ridge release metal ions in rain, which discourage growth on the slope below. They are a preventive measure and not a cleaner. They help where rain runs over them and do little elsewhere, and their effect fades as the strip weathers. Our answer on whether zinc strips stop roof moss sets out the limits.
Method 7: doing nothing
It is a method, and it is sometimes the right one. Moss on a sound roof that is not blocking laps, lifting tiles or filling gutters is often harmless in the short term, and lichen on old slate or clay can be left for decades. Cleaning has a cost and a small risk, and neither is worth paying for a cosmetic gain you do not want. The condition is that the roof is looked at from time to time, so a quiet problem does not become a loud one. A free survey is a low-cost way to find out which side of the line your roof is on.
Side by side
| Method | Speed | Risk to tile | Regrowth | Typical UK cost |
|---|---|---|---|---|
| Scraping and brushing | Slow | Moderate, scratches | Quick | Labour only, varies |
| Pressure washing | Fast | High | Quick, often faster | £553 to £723 |
| Soft washing | Medium | Low | Slower | No reliable range |
| Biocide | Weeks | Low | Slowest | Part of the hand-clean range |
| Hand removal and biocide | Medium | Low | Slowest | £748 to £978 |
Choosing for your roof
The covering matters most. Slate and handmade clay call for the gentlest approach, and a pressure jet is out of the question. Concrete tiles tolerate low-pressure treatment but lose their face under force. Machine-made clay is more forgiving. The comparison in cleaning slate, clay and concrete roofs goes into detail.
The thickness of the growth decides the first step. Thick moss needs hand clearing before anything else, or the treatment will not reach the tile. Light algae and lichen on sound tiles may need only a treatment, or nothing.
The condition of the roof decides whether to clean at all. A roof with slipped or cracked tiles, failing ridge mortar or leaking flashings needs repair first. Cleaning over faults hides them and sometimes makes them worse.
Access and budget play a part. A tall house needs scaffold, which adds cost. A bungalow with a clear garden can be done more cheaply. Whichever method you choose, get gutters cleared at the same time, because the moss ends up there, as our guide to moss and drainage explains.
Mistakes we are called to put right
A few errors turn up again and again. Pressure washing a concrete roof until the colour has gone. Scraping moss off with a wire brush and leaving the roots. Spraying bleach or a garden weedkiller that stains tiles and kills the border below. Cleaning a roof with a slipped tile and then wondering about the leak. Leaving the dead moss in the gutter to block the downpipe. Treating the roof the week before heavy rain. Hiring someone who cannot say what product they use. None of them is hard to avoid with a plan and a survey.
Questions to put to anyone who quotes
Ask what the method is, in plain words. Ask whether a jet is involved and at what pressure. Ask what is applied, how long it needs to work and what the label says about run-off. Ask how the roof will be reached, and whether gutters are included. Ask what the roofer will do if they find a cracked tile or soft mortar. Ask what comes with the job in writing. A cleaner who answers these easily is likely to have done the work before.
Timing and aftercare
Spring and early autumn suit most methods, with mild damp weather and no frost. Our answers on the best time to remove roof moss and whether a roof can be cleaned in winter go through the season. Afterwards, clear gutters, trim back overhanging branches and look at the roof each year. A light repeat treatment costs less than a heavy clean, and the question of rhythm is covered in how often a roof should be cleaned.
What we recommend and why
We generally recommend hand removal of thick growth, followed by a low-pressure biocide treatment, on most tiled roofs. It balances cost, protection for the tile and length of result. We do not recommend a pressure jet on a pitched roof. On a lightly lichened roof in good order, we may recommend doing nothing.
The free survey identifies the covering and the growth, notes any repairs the moss is hiding and photographs it all. You then get one fixed written quote for the method we advise, and the work is covered by our written ten-year workmanship guarantee. For more on the service, see roof cleaning in Basingstoke. A quote starts with a visit, and you can arrange one by calling 01256 213956.
