Question answered
Can a ridge leak?
The short answer
Yes, a ridge can leak. The usual causes are cracked or crumbling bedding mortar, gaps where ridge tiles have shifted, and a torn or sagging underlay beneath the ridge. Rain driven by wind passes through those weak points and runs down the timbers. The lasting repair is to rebed or refix the ridge and renew any damaged underlay, not to coat it with sealant.
Water can get in at the crest of the roof, and when it does the stain often shows lower down. Finding the real entry point is most of the job.
How a ridge normally keeps rain out
The ridge marks the top of the house, where the two slopes rise to meet. Ridge tiles sit over that crest and close the gap between the slopes, but they are not the only protection. Beneath them, the underlay folds or laps over the apex, and that layer carries away any water that gets past the tiles.
So a sound ridge works as a system: tiles that shed most of the rain, bedding or clips that hold them in place, and an underlay that catches the rest. Ventilated ridges add a gap for air as well, which the repair has to leave working.
A leak means one of those layers has failed, and wind-driven rain exposes the weakness at the top of the building first, long before the lower slopes show anything.
Mortar gaps and shifted tiles
Traditional ridge tiles are bedded in mortar, and over many seasons that mortar cracks, shrinks and falls away. Gaps open between the tile and the bed, and between tile and tile. Rain blown sideways enters those gaps and gets below.
Check the gutter and the paths beneath for grit and flecks of old mortar, which drop as the bed breaks down; they are a useful early clue.
Movement in the tiles makes it worse. A tile that has slipped leaves a wider slot, and a hairline crack lets in water pushed by the gusts. The result may be no visible hole at all, just a slow trickle in storms.
BS 5534, in its 2014 revision, asks for a fixing beside the mortar, so a ridge held by old bedding alone falls behind that standard. Our pages on whether mortar ridges are allowed and laying ridge mortar in cold weather go into how the bed should be made and when it sets badly.
Underlay problems at the apex
Underlay lies over the rafters, below the battens, and is the second line of defence. At the ridge it has to lap properly, stay supported and avoid being pierced by fixings. If it is torn, sagging, perished by sunlight through a gap, or simply too short at the apex, water that passes the tiles has nowhere to go.
This fault is easy to miss from outside. The ridge tiles look intact, yet the roof leaks every time the wind shifts into the right quarter. Inside, a stained patch of boarding or damp batten ends near the top of the loft is the clue.
An old underlay may also have been damaged when previous repairs were made. A thorough repair lifts the ridge to check what is below, rather than leaving the tiles in place and hoping the next shower will not find the weak spot.
Why the stain is not under the leak
Water entering at the ridge seldom drips straight down. It slides down the top surface of the underlay, down the rafters or along a purlin and appears wherever it finds a way through. A ceiling stain can sit a metre or more from the real entry point.
In the loft, look for tide marks on the timbers, damp insulation and dark patches on the underside of the felt. Photograph them from a safe position, and note whether the marks line up with the ridge or with something else, such as a chimney or a valley.
Write down when the stain grew, and whether it dried between spells of rain. A stain that stays damp in dry weather points towards condensation or a slow, constant source.
Other causes also fit the picture, and condensation is one we rule out during the survey. Our page on verge undercloak covers another edge where water often gets in, down the sloping side of a gable.
A lasting repair at the ridge
The repair starts by lifting the affected tiles and clearing the old bedding. We check the underlay, the batten ends and the ridge timber, replace what is damaged and then refit the tiles, bedded and fixed mechanically, or switch to a dry-fix system tested to BS 8612:2018.
Sealant or a bitumen strip painted over the joints is only short-term cover. It hides a failed bed and fails again at the next hard blow. If the ridge has deteriorated along its length, relaying it is better value than patching it piece by piece.
Where the ridge is sound but the underlay is not, only the tiles along the affected stretch need lifting, so the work stays in proportion to the fault.
Photographs of your own ridge come with the survey, and the price arrives in writing, as one sum, after we have seen what lies under the tiles. Everything we do at the top of a roof is described under ridge tile repairs.
Ridge leaks: two more questions
Why is my loft damp when the ridge tiles look fine?
From the garden a ridge can look perfectly sound while the bed has cracked or the underlay beneath has torn. Condensation is another possible cause, so the survey checks both. Look for tide marks on the timbers and note whether the damp follows storms.
Can I see a leaking ridge from the garden?
Sometimes. Binoculars may show gaps in the mortar, tiles out of line or a visible slot along the top. Leaks caused by the underlay beneath leave no outside sign, so a loft inspection and a survey of the apex are usually needed.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
10-year workmanship guarantee, in writing.