Can loose ridge tiles cause a leak?

Where two slopes of a pitched roof meet at the top there is a gap. The tiles on each slope stop short of the point, and a row of rounded or angled capping pieces, the ridge tiles, closes it over. Verges and hips have their own seals, so a leak near the ridge can start at either end of the run as easily as in the middle. The mortar bed or a dry-fixed system beneath the capping fills the space and keeps wind and rain out of the roof void.

Below the tiles sits the underlay, a membrane that carries any water slipping past the tiles down towards the gutter. The ridge is meant to work with it by covering the top edge of both slopes, so rain is not driven into the gap above the underlay. If the capping moves, that cover goes with it, and the underlay is left to do a job it was never meant to do alone.

There are a few routes. A crack in the bed lets water run into the gap and trickle onto the batten and rafter below. A tile that has slipped sideways leaves an open section along the line. A tile that has fallen away completely exposes the top courses of both slopes, not only to rain blown sideways but to rain falling straight down. A cracked capping tile leaks differently from a slipped one: the break lets water through the piece itself, even when the bed beneath looks sound.

Wind makes matters worse. Driving rain blown along the roof can enter a small gap with real force, and sea weather on this coast gives it plenty of chances. A gap that stays dry in a light shower can pass water freely in a gale, which is why a roof that seems fine for most of the year may leak only when the weather turns. If yours does, mention that when you call, because it points the survey at the ridge and the verges.

Water that gets in at the ridge seldom falls vertically. It travels along the underlay, down a rafter or across a timber before it finds a way through, so the mark on the ceiling may sit a metre or two from the fault, and lower on the slope. The stain tells you that water arrived, not where it came in.

Guessing at the repair from a ceiling stain can waste money. A look in the loft by daylight, along the rafters beneath the ridge, often shows tide marks or dark patches that lead back to the source. Our answer on checking the loft for a roof leak explains what to look for and how to stay safe while you do it, with a torch and without stepping off the joists.

Not every damp patch is a leak. Moist air from the house can settle on cold timbers and underlay, collect and run down, looking very like a leak after rain. The difference is often timing: a leak shows during or soon after wet weather, whereas condensation tends to follow cold, still spells and a lot of cooking, bathing or drying indoors.

A loose ridge can cause both at once, because a gap lets in rain and also upsets the airflow along the apex. So a survey looks at the tiles and the loft together. If you are unsure which you have, see our answer on whether it is a leak or condensation. A plain verdict from the loft and the roof costs less than treating the wrong cause for a whole winter.

If water is coming in, we treat it as a priority and secure the roof first. That may mean a temporary cover, or securing loose pieces so the next shower does no more harm. Please do not go up yourself: a loose ridge tile can shift underfoot, and a wet roof is a hazard even for people who work on one every day.

The lasting repair follows the survey. Loose tiles are rebedded with a mechanical fixing, cracked ones are replaced, and where a mortar bed keeps failing a dry-fixed system may suit better. The written quote states a single total, and the photographs from the survey show the fault on your own roof, which makes it easier to see why a particular repair is being suggested. See the ridge tile repairs page for the work, or how ridge tiles are fixed for the steps, from stripping the old bed to the last tile.