Can dry ridge go on a slate roof?

1How a dry ridge sits on slate

On a slate roof the ridge pieces are often clay or stone, shaped to a rounded or angled profile, and traditionally bedded in mortar. A dry ridge replaces the bed with a fixing system. A rail or batten runs the length of the apex, the ridge pieces are held by clips or screws fixed back to the rafters or ridge board, and a flexible, often ventilated, roll closes the gap under each side.

The slate itself stays where it is. Depending on the kit, the system fixes through the top course or sits above it, and it has to suit the slate thickness and the headlap in use. That is why the manufacturer's range and instructions come first. A kit designed for concrete tiles does not automatically work on slate, and mixing parts from different ranges is where problems begin.

For the matching detail at the hips, see the dry hip system page.

2How the finished ridge looks

Many slate roofs carry a decorative crest, like the clay finials and cresting on a Victorian villa. A dry system can hold that kind of piece, but the clips and the roll change the line under it. On a plain half-round or angled ridge the result is very close to the original, and from the street the difference is hard to spot. On a heavily moulded crest, the shape of the piece can limit which kits will hold it securely.

Neatness matters more on slate, because the roof is dark and crisp and an uneven seal shows. The roll comes in a limited choice of colours, so we match it to the slate and check the overlap at each joint. On a seaside house the ridge takes weather from every side, so the roll and clips should be specified for exposure by the maker.

If you like the look of mortar lines, a bedded ridge with a fixing hidden behind the mortar is still a sound choice, as our page on ridge re-bedding explains.

3Old slate, conservation areas and listed roofs

Many slate roofs along the Victorian and Edwardian streets near the seafront are old, and some sit in conservation areas or on listed buildings. Re-covering a roof like for like usually sits outside planning control, yet some Article 4 directions take that freedom away. Two such conservation areas, Old Shoreham and Kingston Buci, lost the right to change roof coverings and chimneys on houses that front a road. Check with the Adur & Worthing planning team before altering the finish.

On a listed building, materials that do not match can require listed building consent, so ask the council first. Marley's note on BS 5534 adds that the 2018 amendment accepts that heritage roofs can need a different approach, and it suggests speaking to the council and to conservation advisers.

On a heritage roof, a traditional bedded ridge with a discreet mechanical fixing is often the more suitable answer. The listing officer or council can tell you what they expect, and the survey photographs we provide help them judge it.

4Looking after a dry ridge on slate

A dry ridge needs little attention, but it is not a fit-and-forget item. After a hard winter, scan from the ground for a ridge piece that sits out of line, a roll that has slipped at a joint, or a clip that has worked loose. Moss and lichen can gather on the seal and the slate beside it, and gentle clearing helps keep the line clear.

Do not use a pressure washer on slate or on the seal, because it drives water under the laps and can lift the roll. If something looks wrong, send us a photograph. Early attention to a single loose piece is far cheaper than a gale taking the lot, and the fix is usually a refix of the clip, not a new ridge.

5When a dry ridge is the right call

A dry ridge suits slate where the bed has failed more than once, where mortar keeps cracking in the wind, or where the roof is exposed and the ridge needs a fixing that does not depend on a bond. It also works on newer slate, including imported slate on modern estates.

It is not right where the slate is fragile or the headlap is tight. Cracked or slipping slates are repaired first, because a ridge is only as secure as the slates beneath it. We check that from the loft and on the roof, and the photographs show you the same view.

Roof edges raise similar questions, which we cover in fitting dry verge to an old roof. For the time a job takes, see how long a ridge repair takes. The full service sits on the ridge tile repairs hub.