The short answer
Ridge tiles usually come loose because the mortar bedding beneath them has cracked or crumbled with age, frost and movement, leaving the tiles sitting on a weak joint with no mechanical fixing. A rocking or gapped ridge tile is worth putting right soon, because wind can lift it clear and rain can then reach the roof timbers.
What a loose ridge tile is actually telling you
The line where a roof's two sloping sides join is the ridge. The curved tiles laid along it sit on a strip of mortar, and that mortar is the only thing holding most older ridges in place. When a ridge tile rocks under a hand, shows a dark gap along its length or has a visible crack in the joint beneath, the mortar has stopped doing its job.
Loose tiles are a symptom, not the fault itself. The fault is the bedding. Mortar is a rigid, brittle material sitting on a part of the roof that shifts slightly as the weather warms, cools and blows. Over the years it shrinks away from the tile, cracks along its length, and begins to fall out in pieces. You may find crumbs of it in the gutter or on a path below, which is often the first clue anyone notices.
A ridge in this state still looks like a ridge from the street, so the problem can run for several winters unseen. The tiles stay put on a calm day and move on a windy one.
The common causes of loose ridge tiles
Several things work on a mortar bed at once, and on an older roof more than one is usually at play.
- Age and shrinkage. Mortar loses volume as it cures and keeps drying and wetting for years. Hairline cracks open at the edges and widen.
- Frost. Water enters a crack, freezes, expands and levers the joint further apart. A bed that was sound in autumn can be open by spring.
- Wind. A gust lifting at the ridge works a tile back and forth against its bed until the bond breaks.
- Movement in the roof. Timbers swell, shrink and settle, and a rigid bed cannot follow.
- Poor original bedding. A mix that was too strong, too weak or too dry when it was laid will not last. A hard cement mix on a soft clay tile can crack the tile instead of bonding to it.
- No mechanical fixing. Many ridges were laid on mortar alone, with no clip, screw or strap holding the tile down.
That last point matters because current practice has moved on. BS 5534:2014 no longer trusts mortar by itself to secure ridge, hip and verge tiles; tiles set in mortar should also be pinned down mechanically.
How urgent is a loose ridge tile?
Treat a rocking tile as something to book, not something to watch for a year. It does not usually mean water is pouring in today, but it does mean the next strong wind has something to work on.
The risk comes in two forms. The first is a tile coming off. A ridge tile is a heavy, curved piece of clay or concrete, and one that slides down a slope can land on a path, a car or a person. The second is water. Once a tile has gone, the open ridge lets rain in at the highest point of the roof, where it can run down onto the timbers and the underlay, the sheet that sits beneath the battens to catch whatever gets past the tiles.
A few cases move to the front of the queue: a tile that has already slipped, a gap wide enough to see daylight from the loft, or a ridge that has been disturbed by a storm. If tiles are down or hanging we prioritise the call and make the roof safe first, then repair properly once it is dry enough to bed new mortar. Keep people and vehicles clear of the area below until that is done.
What you can check without going on the roof
Do not climb up to test a ridge. A slippery roof edge is the wrong place to find out a tile moves. Most of what is worth knowing can be seen from the ground or from an upstairs window.
Stand back far enough to see the whole ridge line against the sky. A straight line is a good sign. Look for a tile that sits crooked or higher than its neighbours, a dark shadow between the tile and the roof where mortar has dropped out, or a stretch where the ridge dips. Binoculars help, and so does a phone camera zoomed in, which also gives you a record to show a roofer or an insurer.
Then walk round the house and check the ground, the flat roofs below and the gutters for pieces of mortar. A scatter of grit or pale crumbs usually means the bedding is breaking up somewhere above. In the loft, a pinprick of daylight along the ridge line, or stained timber beneath it, says water has been getting in.
None of this replaces a close look by a roofer, but it tells you whether you need one this week or this season.
How a loose ridge is put right
What gets done depends on how much bedding is left. Where only a few joints have cracked and the mortar beneath is still sound, repointing may be enough, and our page on repointing ridge tiles explains where that stops being sufficient. Where the bed is failing along a run, the tiles come off, the old mortar is cleared, and they are laid again on fresh mortar with mechanical fixings added.
We also check the details around the ridge. A cracked or missing tile is replaced with a matching one, the end pieces are looked at, and where hips meet the ridge we check those joints too, which is covered in our note on bonnet hip tiles. Dry-fix is the alternative: the tiles are held by clips and a vented strip instead of a mortar bed, which sidesteps the mortar problem.
For what a repair typically costs, see our guide to ridge repair cost. The wider range of work is described under ridge and verge repairs. You get a free survey with photographs of your ridge, one fixed price on paper, and the finished repair is covered by a 10-year written workmanship guarantee.
