The short answer
Spalling is the face of a tile breaking away in flakes or layers. The usual cause is water soaking into the tile and freezing, which pushes the surface off. Clay shows it as chips and peeling faces, concrete as a roughened, crumbling top. A few spalled tiles can be swapped. Many on one slope point to a covering nearing the end of its life.
Chips of tile lying on the lawn or the drive are the first sign. What matters next is how deep the damage goes and how many tiles are affected.
What spalling is and what causes it
Spalling comes from moisture. A tile takes up a little water, the water freezes in a cold spell, and ice needs more room than water. Repeated freezing and thawing pushes at the tile from the inside until the outer face lets go. Damp, shaded slopes under trees stay wet longest and suffer most. A slope that never sees the sun can stay cold and wet for days after the rest of the roof has dried, so it takes more freezing cycles than its sunny neighbour.
What usually makes tiles crack?
Frost is one cause, though not the only one. Footfall on a slope, a slipped tile knocking its neighbours, a fixing rusted tight and a falling branch all crack tiles. A crack is a break right through the tile, often in a line. Spalling is loss of the surface. The two can occur together, and a tile that has flaked is easier to crack later.
Look at what has landed on the ground. Thin curved flakes mean surface loss. Chunks and straight breaks mean cracks. Our answer on the cracked roof tile deals with the second kind, including the steps worth taking before a repair is booked.
Clay against concrete
The two materials fail in different ways. Clay is fired, and the quality of a tile depends on the clay used and how it was burnt. A well-fired clay tile can resist frost for generations, while a soft one, or one laid on a permanently damp roof, may start to peel. Spalled clay often shows a paler, rougher patch where the glaze or the outer skin has gone, and the exposed body soaks up water faster than the face it replaced. Concrete tiles are cast from sand and cement, and weathering shows as a rougher surface and a thinning of the coloured layer on top.
Do both materials wear out at the same rate?
The published figures differ. Marley puts its concrete roof tiles at around 60 years of expected life, with no guarantee implied. The BRE minimum life expectancy of 60 years is for clay tiles only. For old peg tiles, the conservation literature says that figure is not a dependable guide. A tile past its best may spall across a whole slope, which is a different matter from one bad tile at the eaves.
You can read more in how long a tiled roof lasts, and a roofer can show where the surface has thinned by comparing a shaded slope with a sunny one.
When spalled tiles need replacing
A tile that has lost only a thin skin of surface can go on shedding water for years. One that has flaked through to the body, or whose face is so thin it breaks when touched, cannot.
How do I decide between replacing and leaving?
Three tests help. Does the damage go deep? Does it spread across many tiles? Is there water in the loft? If the answer to the last is yes, act. A tile that spalls at its bottom edge, where it laps over the tile below, can let water through even when the face looks fair from the ground.
For a few tiles, replacement is the answer. MyJobQuote gives £150 to £200 for five tiles and £200 to £275 for 10 to 20 as typical UK ranges (Oct 2026). When whole slopes are going, patching adds up and a re-roof can be the better buy. We go up, take photographs of the weakest slope and say which route we would choose, giving our reasoning in plain terms.
Matching new tiles to the old roof
A replacement tile has to be the same profile, size and fixing as its neighbours. Colour and texture are the hard part, because a new tile on a weathered slope shows as a bright patch until it ages.
Is it possible to find a matching tile?
Often, with a little searching. A reclaimed tile from a sound slope or a salvage yard is the best match for old clay. For a more recent concrete roof, the maker may still sell the same tile. Where nothing matches, we put new tiles on a rear slope and move sound old ones to the front, so the street view stays intact.
See matching old roof tiles for the detail. Owners of listed houses, or houses in a conservation area, should ask Somerset Council's planning team about consent before the covering is altered. The pitched roofing page lists our work. Whichever route suits your roof, you receive a single price in writing once the survey is done.
More on flaking tiles
Is moss behind the flaking on my tiles?
Moss holds water against the tile, which keeps it wet and gives frost more to work on. It contributes without being the whole story. Removing it gently helps, but a tile already flaking through will not recover. Marley advises against powerful jet washes, which can damage the surface.
Can a spalled tile be painted or coated?
A coating hides a flaking face but does not stop water entering, and trapped moisture can speed the damage. If the tile is sound but dull, cleaning is the first step. If it is flaking, the choice is to watch it or replace it, depending on how deep the damage runs.
The full picture: Pitched roofing in Taunton · More short answers