The short answer
Concrete roof tiles are best cleaned with a low-pressure soft wash that kills the growth, after loose moss has been lifted off by hand. High-pressure jets are the usual cause of surface wear, because they strip the coloured layer and leave a rougher tile that grows moss faster. The tiles are checked for cracks and slipped courses before any washing starts.
Why concrete tiles need gentler treatment than they look
A concrete tile looks solid, and it is heavy, but the part that does the weatherproofing work is the outer skin. The tile is made with a pigmented top layer, and some makers add a factory coating over it. Together they close the pores of the tile and keep rainwater from soaking in. Remove that skin and the tile underneath is plain, porous concrete.
That is what makes cleaning a balancing act. Moss and algae want a rough, damp surface. A tile that has been scoured by a hard jet gives them exactly that, so a roof blasted bright this year can be furred with moss again within a couple of seasons. The cleaned roof ends up in a worse state than the dirty one.
Concrete tiles have been laid on British houses since the middle of the last century, and you will see them on many later estates around Swindon. You can tell them from clay by the flat, matt face, the consistent colour and the even edges. Clay tiles, by contrast, show slight variations in shade and a more irregular edge, and they wear differently when cleaned.
The three ways to clean them
Hand removal comes first on any roof with thick moss. A roofer lifts the cushions off with a brush or a scraper held flat to the tile, working from the ridge downwards so the debris falls into the gutter line and can be collected. Done with care, scraping removes bulk without wearing the face. Done in a hurry, a metal blade gouges it.
Soft washing follows. A biocide is sprayed on at garden-hose pressure and left to kill the roots and the film beneath. The growth turns grey, dries out and loosens over the weeks that follow, and rain takes much of it away. It is slower than a jet, but it leaves the tile skin alone.
Pressure washing is the third route, and the one we avoid on concrete. MyBuilder's roof cleaning guide, updated on 21 August 2026, prices it at £10 to £15 per m² and adds a warning about delicate tiles. It also drives water sideways under overlaps, which can wet the underlay and the battens beneath. Our page on pressure washing roofs goes into the risks in more detail.
What each method costs
The same MyBuilder guide gives manual scraping at £5 to £10 per m² and soft washing at £15 to £20 per m², with overall bands of £400 to £750 for a tile roof and £450 to £850 for a pitched roof. Those are typical UK figures from one national guide, set out here so you can judge a quote when it arrives, not as a price for any particular house.
| Method | Typical UK rate | Effect on concrete tiles |
|---|---|---|
| Manual scraping | £5 to £10 per m² | Gentle if done flat and by hand |
| Soft wash with biocide | £15 to £20 per m² | Leaves the surface skin intact |
| Pressure wash | £10 to £15 per m² | Can strip the face of the tile |
A low rate can still produce an expensive outcome. Replacing tiles early because a harsh clean wore them out would swallow the gap between those three rates many times over. Access also counts: a roof that needs a tower or scaffold will cost more than the per-metre figures suggest, whichever method you choose.
Signs a tile has already worn too far
Run a hand over a spare tile if you have one in the garage. A sound concrete tile feels smooth and slightly waxy. A worn one feels sandy, sheds a fine grit onto your palm, and shows the colour fading in patches, often with the aggregate visible. Water that once beaded now soaks in and darkens the tile.
Worn tiles still do their job for a time, which is why a clean can be reasonable. But the surface will not recover, and moss will return faster than it would on a sealed tile. Sources vary on how long concrete tiles last, so a safe range is often 30 to 60 years, and a roof near the top of that range deserves a realistic conversation about repair against replacement before money goes into cleaning.
Cracked tiles, chipped nibs and slipped courses are the other thing to look for. A tile with a cracked head can slide out when it is walked on or scraped, so it is better found on the survey than during the wash.
How we approach a concrete roof
We start with the survey and photographs of the slopes, then agree whether the roof needs a clean at all. If the tiles are in good order, we lift the thick moss by hand, apply the biocide and leave it to work. If the roof is crumbling, we tell you plainly and talk through patch repairs or a strip and re-tile, whichever properly solves the fault. You receive a written price after the visit, and the labour is backed by our ten-year guarantee on workmanship. Afterwards we leave the garden tidy and carry the moss away with us.
After cleaning, a coating can slow regrowth, and that decision is covered in our page on black streaks on a roof. For the other treatments we offer, the main roof cleaning and moss removal page lists them all, and the page on why moss grows explains why some roofs relapse sooner than others.