exterior
Roof cleaning and moss removal
Roof cleaning costs £400 to £900 for a typical semi-detached house and £700 to £1,500 for a large detached one. The single most important thing to know before booking is that a roof should never be pressure washed: it strips the protective granules off concrete tiles and forces water under them, and it is the fastest way to turn a cosmetic job into a roofing bill.
What this covers
What it costs. Roof cleaning costs £400 to £900 for a typical semi-detached house, £700 to £1,500 for a large detached one and £15 to £25 a square metre where a firm prices by area. Full cost breakdown.
What the job covers
- Moss removal by hand scraping, which is the method that does not damage tiles
- Soft washing with a biocide to kill the regrowth
- Clearing the gutters afterwards, because the moss ends up in them
- Ridge and verge checks while access is up
- Applying a residual treatment that slows it coming back
What is involved
The right method is scraping and soft washing. Moss is removed by hand with a scraper, then a biocide is applied at low pressure and left to kill what remains, with the regrowth dying back over the following weeks. It looks slower and less dramatic than a pressure washer and it is the reason the roof still has its surface afterwards.
Concrete tiles are the case that matters. They are made with a coloured granular surface, that surface is what sheds water and resists moss, and pressure takes it off. A pressure-washed concrete roof looks clean for a season and then goes green faster than it ever did, because the surface that was slowing the moss has gone.
Whatever comes off the roof lands in the gutters, so gutter clearing belongs in the quote rather than in a separate call the following week. And because access is already up, it is the cheapest opportunity anybody will get to look at the ridge, the verges and the flashing.
Choosing someone for the job
Ask directly whether they pressure wash roofs. If the answer is yes, that is the end of the conversation.
Ask how they access it: scaffolding, a tower or a cherry picker, and who is paying for it. Access is often the largest single line in the price.
Ask whether gutter clearing and a biocide treatment are included, and get both on the quote.
Common questions
Does moss actually damage a roof?
It holds water against the tiles and lifts them slightly, and it blocks gutters and valleys. On a sound roof it is slow; on an old one it accelerates what is already happening.
Why not pressure wash it?
Concrete tiles carry a granular surface that sheds water and slows moss, and pressure removes it. The roof looks clean for a season and then goes green faster than before.