The short answer
Cracked tiles come from frost working into damp clay or concrete, from weight on the roof such as ladders and aerials, from impacts like branches and falling debris, and from tiles held too tightly or on movement in the structure. One cracked tile is a quick replacement. Many across a slope points to a covering nearing the end of its life.
Frost, water and age
Tiles of every material take in a little water, and water expands as it freezes. A tile that is saturated when a hard frost arrives can crack along a weak point or lose a layer from its face. Met Office averages for South Farnborough (1991 to 2020) show around 53 air-frost days, so a roof here goes through the freeze and thaw cycle many times a winter.
The cycle does its worst to tiles that are already weakened. A hairline crack that took on water in autumn can widen in January. Age plays a part too, since older tiles are more porous and more brittle than new ones.
Look at where the cracks are. A scatter across a slope, particularly along the lower courses or on the shaded side, often means the tiles themselves have aged out. A single crack in an otherwise sound slope is more likely a one-off event.
Moss holds water against the surface and keeps tiles wet for longer, which feeds the problem. Our page on repairing a clay tile roof looks at how frost damage shows on clay specifically.
Foot traffic and impact
A tile is strong against rain and weak against a point load. Stepping on a tile, setting a ladder against it, resting a scaffold board on it or kneeling to reach a chimney can snap one that looks perfectly sound. The crack may not show for weeks, until water finds it.
Aerial and satellite dish fitters, chimney sweeps, gutter cleaners and solar installers all spend time on roofs, and any of them can leave a cracked tile behind. Walking on tiles safely is a skill, and our page on whether you can walk on a tiled roof explains how it is done and why a ladder and a roof ladder are not for amateurs.
Impacts come from the sky as well. A branch in a storm, a thrown ball or a piece of falling masonry from a chimney can crack or shatter a tile in an instant. The damage is usually obvious from the ground in the form of a gap, a displaced tile or fragments in the gutter.
A tile cracked by impact has an obvious cause and rarely signals a wider failure. The repair is to replace it and check its neighbours, since the ones either side are often cracked too.
Fixings and movement
Sometimes the tile is not the problem. A tile that is nailed too hard, or held down by a clip that pulls it into the batten, is stressed from the day it goes on. When the roof structure moves a little, as timber does with the seasons, that tile cracks.
Wrongly sized or misaligned battens do the same. A tile sitting on an uneven batten rocks under load and cracks where it should lie flat. Rusting nails swell as they corrode and can lever a tile upwards until it breaks.
These are fixing and structure faults, and replacing the tile alone will not cure them. The new tile is held the same way and cracks the same way. Our survey looks at the battens and the loft side of the slope for clues, such as light showing through, sagging timbers and rust.
BS 5534 sets out how tiles should be fixed, and Marley points out that installing to BS 5534 is not required by law. A careful roofer works to it anyway. Where fixings are the issue, we correct them as part of the repair.
If cracks keep returning in the same place, say so when you ring, as it points to a cause beyond the tile.
Replace, patch or re-tile
A single cracked tile is replaced, not patched. Sealant, tape and mortar smeared over a crack are not a lasting answer, and they hide a failing tile. The broken one is lifted out and a matching tile is fixed in its place, using the clip or nail that its position on the roof calls for.
On cost, Which? (Nov 2025) puts a small job of up to six tiles at £75 to £400, ex VAT. MyJobQuote (Oct 2026) averages around £215 for five tiles. Both are typical UK ranges from national cost guides, and access moves the figure more than the tile does. See our page on roof tile replacement cost for more.
If many tiles are cracking, a patchwork of repairs costs more over time than the work it postpones. At that point we talk about re-tiling the slope, reusing sound tiles where we can.
Photographs of the damage come first, then a single written total. Rain coming through gets a temporary cover straight away. The wider pitched roofing hub explains the covering choices we work with in Farnborough and the towns around it.
