Moss on the roof invites a weekend project. A bucket of treatment, a long-handled brush and a ladder seem a small outlay against a quote of several hundred pounds. For some low, simple roofs that sums up fairly. For most houses it does not, because the true cost of cleaning a roof yourself includes a fall risk, a chance of cracked tiles and a good chance of doing the job twice. This guide sets out both sides evenly, so you can make the decision on facts, and it tells you plainly when we would not want you on the roof.
What professional cleaning costs
Published UK cost guides report typical ranges for the two common methods. Hand removal of moss with a biocide treatment is reported at £748 for a small roof, £863 for an average one and £978 for a large one. Pressure washing is reported lower, at £553, £638 and £723 for the same three sizes. These are national orientation figures, not a Beacon price list, and the fixed quote that comes with our visit is based on your roof alone. Our page on roof cleaning costs explains what moves the figure up or down.
It is worth noticing that the cheaper method in the list is also the one with the most risk of damage, which is a theme of this page. The price difference between a pressure wash and a hand clean with a treatment is not large, and the second is generally the gentler on the roof.
What DIY costs, honestly
The product and kit are the visible cost: a treatment, a sprayer, a brush, perhaps a ladder. They are modest. The hidden costs sit elsewhere.
Access
Reaching a roof edge from a ladder is not the same as working on the roof. A ladder lets you spray the first few rows of tiles and no more. To clean a whole slope you must be on it, and a wet roof covered in moss is slippery. A professional crew uses a scaffold, a tower or roof ladders that spread the weight and hold on the pitch. Our page on whether roof cleaning needs scaffolding and the guide to roof cleaning safety explain what safe access looks like.
Damage
Tiles crack under boots. Mortar fails under a hard jet. A brush dragged hard across a concrete tile can take off the coloured face. The cost of a repair to a roof you have damaged is almost always greater than the cost of paying someone to clean it. If you are not sure what covers your roof, see our comparison of cleaning slate, clay and concrete roofs.
Getting the chemistry wrong
Not every product that kills moss belongs on a roof. Bleach is a frequent choice at home and a poor one on tiles, as we explain in whether you can use bleach on roof tiles. A treatment that is too weak does little, and one that is applied and rinsed straight away does nothing. Run-off matters too: the wash water flows into your gutters, down your drains and across your garden, and the label sets out what the product can touch.
Waste and mess
Moss that comes off the roof lands in gutters, on paths, on patios and in flower beds. A job done from a ladder by one person with no ground crew leaves a pile of wet green debris, and a blocked downpipe a week later.
The risk question
Falls from ladders and roofs cause serious injuries every year, and the people who fall are often those doing a job they consider routine. A wet, mossy slope is slick. A fragile rooflight, a skylight or an old asbestos cement sheet on an outbuilding will not take a person's weight. Gutters are not a handhold. If you have any doubt about your ability to work at height, or if the roof is steeper than a low garage pitch, leave it to someone with the right access equipment.
Insurance is a second consideration. We make no claims about anyone's cover here, but it is sensible to read your own home policy before taking on a job at height, and to ask any professional you hire for evidence of theirs. Our answer on whether it is safe to inspect your own roof gives practical limits that apply equally to cleaning.
When DIY can make sense
There are cases where a careful homeowner can deal with moss without risk to themselves or the roof.
- A low-level roof, such as a garden shed, a single-storey outbuilding or a lean-to you can reach safely from the ground or a stable platform.
- Light, early growth on a roof in good repair, where a treatment applied from the ground with a pole sprayer is enough and no scraping is needed.
- Routine upkeep after a professional clean, such as clearing leaves from a valley or topping up a treatment on the lower courses.
In each case, a few rules help. Use a product made for roofs and follow the label. Never use a pressure washer on tiles. Keep off the roof surface. Clear gutters first and protect plants. Wait for dry, still weather. And accept that treatment works over weeks, so do not scrape.
When to leave it to a professional
We would not want to see a homeowner attempting any of these.
- A two-storey house, or any roof you cannot reach with your feet on firm ground.
- A steep pitch, or a roof with a valley, dormer, chimney or roof window that you would need to cross.
- Heavy moss that fills the gaps between tiles and has lifted them.
- Slate or handmade clay, which crack and spall when handled roughly.
- Any roof with sheets that could be asbestos cement, such as an older garage or outbuilding. These should not be pressure-washed or scrubbed, and the HSE sets out the rules on its asbestos pages.
- A roof that has leaked, or has slipped or broken tiles, where cleaning could hide the cause or make it worse.
| Factor | DIY | Professional |
|---|---|---|
| Upfront cost | Low, for products and tools | Typically several hundred pounds |
| Access | Ladder only, limited reach | Scaffold, tower or roof ladders |
| Risk of injury | Real, at height on a wet roof | Managed by equipment and method |
| Risk of damage | Higher, from boots, brushes and jets | Lower, with a method chosen for the tile |
| Gutters and mess | Left to you | Cleared as part of the job |
| Roof checked while up there | Rarely | Yes, with photographs |
A sensible DIY method for a low, simple roof
If your roof passes the tests above, the order of work matters. Start by clearing the gutters and covering any plants below with sheeting. Pick a dry day with no rain forecast for at least a day and no strong wind, so the treatment does not blow onto neighbours or wash off. Remove thick, loose moss gently by hand from the laps and from the lowest edge, working downwards and not upwards, so you do not lift tiles. Do not scrape the tile faces or the mortar.
Apply a roof-specific treatment with a garden sprayer to the whole surface, following the label on dilution, coverage and contact time. Leave it alone. Dead moss and algae go brown or black over the next days and then loosen across several weeks. Resist the urge to hose them off. When the growth has gone, sweep the gutters again and note the date, so you know when to look at the roof next. If there is any sign that tiles are cracked, slipped or missing, stop and get them looked at before you do anything else.
If you hire someone, what to ask
A good cleaner will answer these without fuss. What method will you use, and will you use a pressure jet on my tiles? How will you reach the roof, and who will be on it? What do you apply, how long does it take to work, and what does the label say about run-off and pets? Will the gutters be cleared at the end? What do you do if you find a cracked tile or failed mortar? And is the price fixed, in writing, before work starts? A cleaner who cannot say what is on the tiles or how they will get up there is not one to hire.
The benefit people forget: someone looks at the roof
When a professional goes up, the clean is only part of the visit. Moss often hides slipped tiles, cracked ridge mortar, split flashings and blocked valleys. A person on the roof sees them. A person at the bottom of a ladder with a sprayer does not. Many of the repairs we recommend after a survey, from re-pointing a ridge to replacing a split tile, start as a note made while looking at the roof for another reason. If you clean it yourself, you give that chance up, and the problem can wait until it leaks.
The reverse also applies. Occasionally we advise leaving a lightly mossed roof alone. Moss that sits on sound tiles and does not block anything is not an emergency, and our answer on whether moss on roof tiles is a problem sets out when to act and when to wait.
How to decide
Ask yourself five questions. Can you reach all of the affected roof with your feet on firm ground, or a stable platform? Is the roof covering one you know, and one that tolerates a brush? Is the roof sound, with no slipped or cracked tiles? Is the growth light? Do you have the time to treat, wait and clear up properly? If every answer is yes, a careful DIY job may be reasonable. If any is no, a survey will cost you nothing and may save the roof.
The survey costs nothing, and the report that follows pairs roof photographs with a single fixed price. We say so if a few hours of careful work by you will do the job. Where we do the cleaning, the work is covered by our ten-year workmanship guarantee in writing, and we take the debris away. See our roof cleaning in Basingstoke page for more, and if you are weighing it up, ring 01256 213956 and set the quote beside what the kit and a spare weekend would cost you.
