Can a cracked ridge tile be repaired?

1Hairline craze, through-crack or broken in two

Not every mark is a crack. Old clay ridges often carry a network of fine lines in the glaze or surface, and these are cosmetic. A through-crack is different: it runs the full thickness of the tile and may show daylight or dark shadow when you look along it with binoculars.

Position matters as well. A crack across the width of the tile, near the middle, usually means the tile has flexed under wind. A break at one end often means the bedding underneath has failed and the tile is no longer supported evenly along its length.

If a crack has moved apart enough that you can see a stepped edge, or a piece has dropped away, treat it as a broken tile rather than a cracked one. The page on a ridge tile that has fallen off covers the urgent steps, including how to keep the ground below clear.

Note also whether the crack lines up with the joint between two tiles. A split that follows a joint suggests the whole run is moving, not just one tile.

2Why a sealed crack does not stay sealed

Sealant, bitumen tape and a smear of mortar all sit on the surface. The tile beneath them still moves with wind and with changes in temperature, so the filler splits along the old line within a short time. Water that gets into a crack in cold weather can also widen it as it freezes.

A patch can also hide the problem. Once the crack is covered it becomes harder to tell whether the tile has moved, and the bedding underneath may have dropped away unseen. A crack that has been painted over is a poor guide for anyone inspecting the ridge later.

There is a place for a temporary seal, for instance to keep rain out until a tile can be sourced. It should be described as temporary and replaced, not left in place as the repair and forgotten about for the next few winters.

3Matching the replacement tile

Ridge tiles come in several profiles and in clay or concrete, and a replacement has to match the profile, length, colour and the way the ends overlap. A tile of the wrong shape will not seat on the bed, and a tile of the wrong colour stands out for years.

Weathering is the usual difficulty on an older roof. Clay darkens and mellows, and concrete tiles lose surface colour, so a new tile looks bright beside its neighbours. Where an exact new match is not available, a reclaimed tile of the same type is sometimes the better choice, or a tile from a less visible stretch can be swapped to the front and the new one placed out of sight.

Hip tiles follow the same logic. Our page on hip tile repairs deals with the sloping runs, where gravity adds its own pull to each tile.

4How a single tile is swapped

The cracked tile is lifted off, and the old mortar bed under it is cleared so the new tile sits on a clean, sound base. We check that the tiles either side are secure before going further, because a failed bed rarely stops at one tile.

The new tile is then bedded and fixed. BS 5534, in its 2014 revision, asks for a fixing of its own beside the mortar bed, so the new tile is screwed, clipped or otherwise held down. On a dry ridge system, a clip or bracket does that job without any mortar. The joints are finished tidily so rain runs off cleanly.

Survey photographs let you see the cracked tile, the cleaned bed and the finished joint, which makes it clear what was done and why. The price is given in writing, as one total, once we have looked along the whole run rather than at the one visible fault.

5When one crack points to a bigger repair

Several cracked tiles on one ridge usually mean the bedding has aged across the run or the ridge is moving. Replacing tiles one at a time then becomes a repeat job. Relaying the length, or fitting a dry-fix system, deals with the cause. Whether you could attempt it yourself is answered in can you replace ridge tiles yourself.

The gable ends are worth checking in the same visit, because the same weather that cracks ridge tiles can lift verge caps. Blown dry verge caps are a separate failure with their own repair.

Anywhere you see a tile slipping, or hear one rattle on a windy night, report it early. A modest tile swap now is far better than refixing a long run after a storm. The whole range is set out under ridge tile repairs.