What causes slipped roof tiles, and how are they fixed?

A tile never slips for no reason. It slips because the fixing that held it has given up, or because the timber under that fixing has. Over the years nails can loosen as the batten around them dries and shrinks, and clips can lose their grip. A gale then finds the weakest tile and lifts it, or a whole run of tiles creeps down the slope together.

Wind does more than push. Marley notes that on a pitch below 30 degrees the windward slope can suffer strong suction, so a badly fixed tile on a shallow roof is pulled up as well as pressed down. Gales coming in off the sea make this a worry along the whole coast, and it is the reason the fixing counts for more than the tile. Tiles along the verge and the eaves are the most exposed, because the wind gets under them first. A tile that has slipped once is telling you something about what lies behind it.

Three faults sit behind most slipped tiles. The first is nail sickness, where the fixings corrode or work loose and tiles drift out of position. The second is rotten battens, the timber strips the tiles hang from, which no longer grip a nail. The third is a torn or perished underlay, which lets water in and softens the timber over time. Our answer on rotten roof battens covers the second of these in detail.

Roof spread is rarer but worth knowing about. If the walls or rafters are moving apart, tiles can shift as the roof opens along the ridge. A bowed ridge line or a wide gap at the eaves points that way. A look from the ground will not settle it, which is why we inspect the slope from above and take pictures of what we find before we say what is wrong, rather than guessing from the garden.

The repair begins with the cause. We raise the neighbouring tiles, then look over the batten, the nails and the underlay below, renewing whatever has deteriorated. Then the tile goes back, or a matching one goes in, with a fixing that will hold. Wienerberger asks for a minimum of one mechanical fixing per single-lap tile, and clips on tiles along exposed edges are normal practice.

If one batten is soft, we cut it back and splice in a sound length instead of driving a nail into rot. If several tiles have gone along one line, we look for a wider fault and tell you before any price is given. Our page on roof tile clips explains when a clip is the right answer and when the batten or the tile itself needs attention first. A tile that is whole can go back, but a cracked one is replaced.

Do not climb up to push the tile back. Tiles are slippery and brittle, and a fall from a ladder onto a path is the most serious risk in the whole job. Stand in the garden and look up, using binoculars if you own a pair, and note which slope the gap is on and roughly where. Take a few pictures from the ground, because they help both a roofer and, later on, an insurer.

If the gap sits over a bedroom, or the loft is already damp, tell us when you ring, because we prioritise leaks and storm damage. Set a bowl beneath any drip and clear furniture away from it. Covering an open gap for the time being is work for a roofer, never for a homeowner on a ladder. Slipped tiles often drop to the ground, so keep the ground below clear of people until the roof has been checked.

After a storm, Which? suggests ringing your insurer at the outset and keeping the receipts from any emergency visit. Whether a policy pays depends on its terms and on whether the damage came from a storm or from age. Our answer on home insurance for slipped or missing tiles goes through it, and nobody can promise that a claim will succeed.

On price, Checkatrade's roof repair guide gives typical national figures per square metre, £90 to £120 for concrete and £110 to £160 for clay, with VAT to add, and puts roofers at around £280 to £360 per day. A handful of tiles is a modest job, and a failing run of battens costs more. Where tiles are missing rather than slipped, the same survey applies and the replacements must match the roof. You get a written price after the survey, and our pitched roofing page shows the wider work.