The short answer
Replace the tile. A crack lets water run through to the battens and underlay beneath, and sealant, mastic or paint only hides the line until the tile flexes again in sun, frost or wind. Swapping in a matching tile is a small job that fixes the fault properly. Sealing makes sense only as a short, temporary stopgap while a replacement is arranged.
What a crack really does to the roof
A tile is the top layer of a roof, not the whole waterproofing. Underneath sit the battens, which are the thin timber strips the tiles hang from, and a second line of defence, the underlay, which catches stray drips. A sound underlay copes with the odd drop. A cracked tile sends a steady trickle to the same spot every time it rains, and that spot is usually a batten.
Timber that is wetted again and again goes soft and dark, and the nail that holds the next tile starts to lose its grip. You may see nothing indoors for a long time, because the loft insulation and the underlay soak up the water first. By the time a stain shows on a ceiling, the damp has often been working for months. That is why a cracked tile is worth dealing with even when the house feels dry.
Why sealant is a stopgap and not a repair
Tiles move. They expand a little in sun, shrink in the cold, and flex under wind and under the weight of a roofer's boot. Clay and concrete are both rigid, so a crack that opens and closes pulls at any filler stuck across it. Mastic and bitumen tape cure hard or lose their grip on dusty, weathered tile, and the bond fails along the edge of the crack first.
A sealed tile also looks fixed, which is the real trouble. Nobody checks it again, and water finds its way back under the filler. There is a second issue with frost: if water gets into a cracked porous tile and freezes, the crack widens and flakes the face off. Sealant does nothing about that.
Where a sealed tile can make sense is as a few days of cover. If a replacement tile has to be sourced, a temporary seal keeps the weather out in the meantime. We treat it as a make-safe and describe it that way.
How a single tile is replaced
The job is smaller than most people expect. On interlocking tiles, the tiles on either side and in the course above are eased up a little, the broken tile is lifted out, and a new one is slid in and clipped or nailed. On plain tiles, which hang from nibs on the battens and overlap in a staggered pattern, the neighbours are lifted with a slater's tool and the new tile is slid up into its place, held by the overlap and a nail where the course calls for one.
While the tile is out, the batten and underlay get a look. If the timber is sound and the underlay is intact, the repair is finished in a few minutes. If the batten has gone soft, that is the point where a small repair turns into a slightly larger one, and it is better found now than after the next winter. Our guide to slipped roof tiles covers the sister problem of tiles that have moved rather than broken.
What cracks tiles, and when to look wider
The usual culprits are simple. Someone has walked on the roof, a branch or a satellite-dish fixing has knocked a tile, or age has made the tile brittle. Frost does most of its damage to porous tiles that hold water. A single crack in an otherwise sound roof is a one-tile job.
Several cracks across a slope tell a different story. They suggest the covering is reaching the end of its working life, or that something is putting repeated load on one area, such as a ladder rest or a shared walkway. The type of tile matters too, because plain tiles are thinner and more fragile than interlocking tiles. If you are unsure which you have, our page on plain versus interlocking tiles explains how to tell them apart from the ground. Where cracking is widespread, the survey report spells out whether a patch or a larger repair makes more sense.
Cost and matching the tile
Third-party price pages show roughly what a small tile job costs. MyBuilder's roof repair guide, updated in August 2026, puts a minor roof repair at £100 to £300. Checkatrade's roof repair guide prices clay tile repairs at £110 to £160 per m² and concrete at £90 to £120 per m², with VAT and access equipment left out. A single replacement tile sits at the small end of that, but access can matter more than the tile itself, so check whether any quote includes scaffolding.
The harder part can be the tile. A replacement has to match the profile, thickness and colour of the originals, and older roofs often use tiles that are no longer made. Reclaimed tiles of the same type are a common answer, and a slightly weathered colour blends better than a bright new one. The pitch of the roof limits what is allowed too, which is why our page on minimum tile pitch is worth a look before you change tile type.
Getting a cracked tile looked at
Where one tile has cracked, the fix we recommend is one replacement tile, not a new roof. You get pictures of your own slope after the survey, then our price in writing, and once the repair is done it is covered by a 10-year workmanship guarantee that you hold on paper. We tidy up and take the waste away. If water is coming in today, we deal with that first and plan the lasting repair afterwards.
Back to the pitched roofing hub for the other tile and slate questions, or ring 01793 626096 and send us a photo of the crack.