Loose or Cracked Ridge Tiles: What to Do

Why bedding mortar lets go

A traditional ridge is bedded in sand and cement along the top course of the covering. It is a good system and it has held Irish roofs together for a century, but mortar is rigid and a roof is not. Timber moves with heat and moisture, water gets into hairline cracks and freezes, and each winter opens the crack a little further.

Given enough of that, the mortar gives way. You will often see it crumbling out in sections along one side of the ridge, or missing entirely where a hip meets the eaves. Nobody did anything wrong — bedding mortar is simply one of the shorter-lived parts of a roof, and how long it lasts on any particular roof depends on the exposure and the original work.

What you can safely see from the ground

Stand back across the road or at the end of the garden on a bright day, with the sun behind you. A pair of binoculars is genuinely the most useful roofing tool a homeowner can own.

Signs worth reporting

• A ridge or hip tile sitting higher, lower or out of line with the ones beside it
• A visible gap where you can see daylight or shadow under a ridge piece
• Mortar missing in sections, or a pale crumbly line where it has eroded back
• Pieces of mortar in the gutter, on a flat roof below, or on the ground after wind
• A cracked ridge tile, or one with a corner broken away
• Vegetation or moss growing out of the ridge joint, which means the joint is open
• Staining on the ceiling of an upstairs room close to the ridge line

Ridges, hips and verges

The same failure happens in three places and the consequences differ. The ridge is the horizontal apex. Hips are the sloping edges where two slopes meet on a hipped roof, and hip tiles are the ones most often displaced, because they sit on a slope and the bottom one carries the run. The verge is the gable edge, traditionally mortared, and verge mortar is usually the first mortar on any roof to crack.

A roofer should tell you which of the three is actually failing on your house and whether the rest of the run is sound, rather than quoting for the whole lot by default.

Wind, storms and why ridges go first

Wind does not simply push on a roof; it lifts. The ridge and hips sit along the most exposed lines of a roof, so a ridge piece whose bedding has already failed is often among the first things to move in a storm. Storm call-outs can involve displaced ridge or hip tiles, and a ridge that was already cracked in the autumn is often the one on the lawn after a winter gale.

Storm damage repairs covers the aftermath, and what to check after a storm covers what to look for once the weather passes.

Re-bedding, or converting to dry ridge

There are two sensible ways to put a failed ridge right, and which suits your roof depends on the roof.

Re-bedding means removing the ridge pieces, cleaning off the old mortar and bedding them back in fresh mortar, usually with mechanical fixing where appropriate. It keeps the traditional appearance, which matters on period and slate roofs, and it is often the right answer where the existing ridge tiles are sound and worth reusing.

A dry ridge system replaces the mortar with a ventilated roll and mechanical fixings, so each ridge piece is screwed down rather than bedded down. It does not depend on mortar that can crack and weather, it allows the ridge to ventilate, and it accommodates the movement that broke the bedding in the first place. Dry ridge and dry verge explains where each approach fits and what a conversion involves.

How urgent is it?

A hairline crack in otherwise sound mortar is something to plan for. A ridge piece that has visibly moved, a run with mortar missing in lengths, or anything sitting above a footpath is not — that is work to arrange before the next stretch of wind rather than after it.

Water ingress raises it again. A ridge is the highest point of the roof and water getting in there runs a long way before it appears, which is why the stain often shows up in a room that seems unrelated. Roof repairs and slate and tile repairs cover the work itself.