Horsham stone roofing in West Sussex

Most stone roof repairs begin with the fixings and the timbers rather than the stone, which is why a survey starts in the loft.

A Horsham stone roof can outlast several generations of owners, but the parts that hold it up do not last as long as the stone. Slabs slip when the fixings give way, when a batten behind them softens, or when water and frost have flaked the stone around a fixing hole. So a repair starts with one question: why did that slab move? Putting a slab back onto a rotten batten only moves the leak a few weeks down the calendar. A reliable repair finds the cause, fixes it and then restores the stone.

2.1 Slipped slabs and failed fixings

Many stone slates are held by a peg or a nail through a hole near the head of the slab. When the peg rots or the nail rusts through, the slab slides until its own weight catches on the course below. We lift the slipped slab and its neighbours, check the batten, renew the fixing and set the stone back in its place in the course. Where the batten has gone soft we replace a length of it, because a new fixing in old timber does not hold. On our survey we mark every slab that has moved, not just the one over the stain, and photograph the line it has travelled along. Tell us if water has shown at the same spot more than once; a repeat leak usually means a hidden cause such as a rotted batten or a broken peg.

2.2 Cracked, flaking and missing slabs

A cracked slab can sometimes be left where it sits; one that lets water through has to come out. Stone also flakes in layers, and a slab that has lost its face stops shedding water. Replacements are matched to the old ones by thickness, size and colour, because a thin or pale slab among thick, weathered ones looks wrong and sits badly in the course. Reclaimed slabs from a stripped outbuilding or a neighbouring job are often the best match, since they carry the same weathering. If slabs are flaking across a whole slope, that points towards a re-lay rather than another patch, and the survey photographs show you why.

2.3 Moss, lichen and gutters

Lichen is part of the look of an old stone roof and is usually left alone. Thick moss that holds water against the stone, or blocks a valley, is another matter. We prefer gentle hand work to blasting the surface with a pressure washer, which can strip a worn stone face. Clear gutters and outlets as well, since a blocked gutter sends water back under the bottom course.

A gale can leave a slope open to the rain. We cover it temporarily, make the roof safe first and return for the full repair in settled weather; leaks and storm damage go to the front of our list. Ring your insurer early, take photographs and keep every receipt for temporary cover, which is the advice Which? gives. Bats may roost in old roof voids and are protected by law, so we check for them before stripping any slope, and a nesting bird stops the work too.

Whether stone roof work needs consent depends on the building, its location and what changes, so ask before the first slab comes off.

Like-for-like work on an ordinary house does not normally need planning permission, because the Town and Country Planning Act 1990 says works that leave the outside of a building materially unchanged are not development. Stone roofs are often found on buildings with extra protection, though, so the first question is always whether the building is listed, in a conservation area or inside the National Park. For roofing in Horsham town and the villages around it, the answer shapes the whole job, from the timing to the type of stone.

4.1 Listed buildings

Section 7 of the Listed Buildings Act 1990 bars works that would alter a listed building in any manner affecting its character as a building of special architectural or historic interest, unless they are authorised. The South Downs National Park Authority says regular maintenance and minor like-for-like in-situ repairs do not need listed building consent. Re-laying a slope in the same stone is usually like-for-like. Changing the covering is not, and nor is altering the pitch or the roof structure. Our guide on re-roofing a stone roof in a conservation area goes through permission step by step, and your local council's conservation officer can confirm what applies to a listed home. If you are unsure whether your house is listed, the council's planning team can tell you. What we need from you is simple: the address, photographs of each slope and any listing or conservation-area papers you already hold. From the survey we then write the proposed work up in plain terms that you or your agent can pass to the conservation officer. Timing matters too. Consent decisions take time, and stone often has to be ordered or salvaged, so a planned repair avoids the pressure of working in midwinter.

4.2 Conservation areas and the National Park

Conservation areas and Article 4 directions can remove rights that ordinary houses have, so check with the council's planning team before work starts. Petworth and Midhurst sit inside the South Downs National Park, where Chichester District Council handles applications on the SDNPA's behalf. In the parts of the Park inside Horsham or Arun districts the SDNPA decides directly. Pulborough, Billingshurst and Horsham town are in Horsham District Council's area. Building control stays with the district council even inside the Park, so a re-roof there can involve two bodies: one for planning, one for the Building Regulations.

Churches and monuments

Churches carry their own routes. A Church of England church in use is exempt from listed building consent and goes through the faculty jurisdiction instead; some other denominations run their own procedure. A closed church, or one held by the Churches Conservation Trust, comes under normal listed building control, and a scheduled monument needs scheduled monument consent. Where work on any of these buildings is notifiable under the Building Regulations, we explain which consents apply and handle the notification, and talk through our survey findings with whoever decides.

The right answer is the lightest job that cures the fault, and sound stone is worth keeping on the roof.

After every survey we give one of three verdicts: repair it, re-lay it, or replace the covering. Stone is the one covering where replacement is rarely the first answer, because the material itself is long-lived. Checkatrade says stone slate can last more than a hundred years, and a trade body, the Confederation of Roofing Contractors, gives well-maintained slate 100 years or more. What gives out first is usually the fixings and the battens, and those can be put right without discarding the stone. None of these figures is a promise for your roof, which is why the verdict rests on what we photograph on it. If your roof has been repaired before, the earlier work tells us a lot: mismatched stone, cement-heavy pointing and a patchwork of fixings show where past repairs fell short.

6.1 When repair is enough

A repair is the answer when only one area has failed and the stone and timbers around it are sound: a few slipped slabs, a lifted flashing, a crumbled ridge bed or a blocked valley. We photograph the fault and its cause, fix both, and tell you what to watch for next. A repair also tells us something about the rest of the roof, since the slabs we lift show how the timbers beneath are holding up.

6.2 When a slope needs re-laying

A re-lay means stripping a slope, sorting the stone, renewing the battens and fixings and laying the best slabs back in diminishing courses, topped up with matched stone. It suits a roof where the stone is good but the fixings are failing across the whole slope, and it keeps the look of the building. Our guide on repairing, re-laying or replacing a Horsham stone roof sets the choices side by side.

6.3 Weight, structure and approval

Stone is heavy, and the roof structure was built for it. Where a new covering would add 15 per cent or more to the weight on the roof, the Planning Portal says a building control application is needed, and it advises a structural engineer or surveyor where a replacement is significantly heavier or lighter. It also says no application is normally needed when less than 25 per cent of the total building envelope and less than 50 per cent of the roof is affected. Swapping stone for tile or slate lightens the roof, changes the building and may need consent; check with your building control body first.

Under Approved Document L, replacing a roof covering can count as renovation, and if over half the roof area is renovated, the insulation can need to be improved. The 2021 edition applies until 24 March 2027, when the 2026 edition takes over. You will hear at the survey whether that is likely on your roof, because it changes both the work and the cost. For a listed or conservation-area home, ask the council before any change of covering is even priced.