Ridges on Horsham stone roofs

1Stone or clay along the top

The Stone Roofing Association (SRA) guide notes that the ridge on a Horsham roof may originally have been of stone, but accepts that clay tiles are used today. It gives a practical reason: clay ridge tiles can be ventilated, which stone ridges struggle to do.

Ventilated clay ridges are described as acceptable where clay ridge tiles have already been used on the existing roof. For stone ridges the guide says that ventilation is difficult and suggests contacting the SRA for advice.

That point matters more than it first seems. A stone roof sits over a loft that needs to breathe, and the way the top is finished affects whether damp air can escape. If the roof has been insulated or sealed in mortar, the question of how air reaches and leaves the ridge becomes part of the design, not an afterthought.

Ventilation and appearance are linked here, and the choice is rarely one of taste alone. It follows whatever the roof carries today and whatever that roof needs.

2How much mortar should show

The guide is firm about restraint. Ideally the bedding mortar should not show along the ridge at all, though with uneven stones that is often not possible. The visible depth of mortar should always be kept as small as possible.

To get there, the ridge tiles or stones should be allowed to follow the line of the ridge, instead of being built up with extra mortar to force a dead-straight line. Mortar should be neatly struck off as the work proceeds and not pointed up afterwards.

For new stone ridges, the SRA suggests a vertical wing edge, which allows a neater finish with less visible mortar.

A thick, flush mortar roll along the top is the opposite of this. It looks heavy, cracks as the roof moves, and sheds pieces into the gutter. Where we find one on a stone roof we ask whether it was a later repair that went beyond the original detail, and what has been hidden beneath it.

3What BS 5534 means for a heritage roof

Under BS 5534 as revised in 2014, bedding alone no longer holds the ridge: clips, screws or similar fixings do part of the work. Marley adds that following BS 5534 is a matter of good practice and no statute forces it.

Old roofs call for more care. Marley observes that an amendment published in 2018 makes clear that historic roofs sit awkwardly with some recommendations, and it sends owners to the council and to heritage advisers.

In practice, that means the fixing and the look both have to be considered. A concealed mechanical fixing can hold a clay ridge without changing its appearance, but how it is done on a historic roof is a decision to make with the building in mind, not by default.

Where the ridge has been rebuilt in plain mortar and is starting to lift, a secure fix is often wise, and we explain the options at the survey.

4When consent is involved

Planning permission is not usually required when a roof is renewed like for like, though listed buildings and some Article 4 areas are exceptions. The ridge forms part of the covering, so the same rules govern it.

Listed buildings are the clearest case. The councils' guidance on listed buildings counts a repair made in unmatched materials as work needing consent, and the SRA states that any change to a listed Horsham roof will require listed building consent.

Some conservation areas have extra controls. Article 4 directions cover Old Shoreham and Kingston Buci, withdrawing permitted development for roof coverings on homes that front a road or public path. Worthing's Warwick Gardens has a direction of its own, about altering a slope's shape or material where it fronts the street or open space.

Ask the planning team before work starts if you are unsure which applies. Our page on stone roofs in conservation areas goes into more detail.

5Ridge faults that cause leaks

Typical faults are cracked or missing bedding, ridge pieces that have shifted, and gaps where the ridge meets the last course of stone. Rain driven along the top then finds its way down the first joint it reaches, and a ridge that has been disturbed in one gale is easy to disturb again in the next.

A fault at the ridge can show as a stain well below it, because all the water on that slope passes this line, a pattern described in leaking stone slate roofs. Stones in the highest courses are also the smallest, which our page on diminishing courses explains, and small slabs are the easiest to disturb.

The survey covers the loft and the roof, and you receive photographs of the ridge itself, then one written price. Cost depends on length, access and how much bedding must be redone, and the service is covered at Horsham stone roofing.