Solar panels on a Horsham stone roof: what changes, and what doesn't

Horsham, West Sussex is our own district. Washington, where the vans live, is a village inside it, and the town is thirteen road miles up the A24. So when people ask what is different about solar in Horsham, the honest answer is: mostly the roofs, and one planning rule that nearly everyone has heard wrong.

What Horsham stone actually is

It is a sandstone, split into thick slabs and laid in diminishing courses, heavy enough that the roofs built for it have the timbers to prove it. It is also brittle and irregular. A standard roof hook, which is designed to slide under a tile and screw to a rafter, has nothing predictable to slide under and a slab that can crack if you lift it wrong.

That is why our answer on a Horsham stone roof is almost never a standard hook. The design changes, the fixing changes, and sometimes the decision changes. Which brings us to what the survey is for.

What changes on the day

• The fixing. The mounting has to be chosen for the slab, not from the catalogue, and sometimes the honest design keeps the array off the stone slope altogether and uses a tiled extension, an outbuilding or a flat roof.
• The time. Working on a stone roof is slower. The quote reflects it, and a quote that does not is a warning sign.
• The scaffold. Stone roofs tend to belong to older houses in and around the conservation areas, where access from the street is tighter. Scaffold is in our quote, always.
• The structure. A roof carrying stone already carries a great deal. A survey that does not look at the timbers is not a survey.

What does not change

The electrics, the inverter, the battery, the network notification and the paperwork are exactly the same as on a modern tiled estate roof in Broadbridge Heath. UK Power Networks is the network operator for the RH12 and RH13 postcodes, and the industry code sets the notification threshold at 16 amps per phase, which is 3.68 kW: up to that is a G98 notification, above it a G99 application has to be approved before the system is energised. The MPAN on your bill confirms the operator, which matters because the RH14 side of the district around Billingshurst is on Scottish and Southern Electricity Networks instead.

The planning rule people get wrong

Horsham District Council lists 39 conservation areas, four of them in Horsham town itself: the town centre, London Road, Richmond Road and Park Terrace Gardens. The assumption is that solar panels inside one need planning permission. Under the national permitted-development rules they usually do not.

What the regulations exclude in a conservation area, or in the South Downs National Park that covers the district’s southern strip, is a panel installed on a wall, balcony or roof enclosure that fronts a highway, and since December 2023 a flat-roof array on that kind of land needs prior approval. A panel on a roof slope, even a street-facing one, stays permitted development. A listed house is outside the permitted-development class altogether and needs listed building consent. An Article 4 direction can remove roof rights in a specific area, so we check the address against the council’s conservation area maps before the survey and tell you, in writing, whether anything has to be applied for.

The council’s own position

Horsham District Council declared a climate and ecological emergency in 2023, with a net zero target of 2030 for its own operations and 2050 for the district. Its energy advice pages point residents to the West Sussex Affordable Energy service for grants and schemes, and they carry a plain warning about energy scams: unsolicited contact, urgency, pressure to pay quickly. We would add one line to that list. A solar company that quotes a Horsham stone roof without standing on it is not quoting your roof.

If you are in the district

Our page for solar panel installers in Horsham covers the district’s roofs, the National Park strip, the network operators and what we take into account before a quote. The survey is free, and on a Horsham stone roof it is the whole job.