The 39 conservation areas in Horsham District, and what they do to an extension

Most people find out their house is in a conservation area at the worst possible moment — after the drawings are done, when somebody mentions it in passing. It is worth checking first, because inside one, several of the permitted development rights people assume they have simply do not exist.

Horsham District has 39 conservation areas. Four of them are in Horsham town itself.

The full list

Adversane, Amberley, Billingshurst, Blackstone, Bramber, Coldwaltham, Cowfold, Crabtree, Edburton, Greatham, Hardham, Henfield, Horsham (town centre), Horsham (London Road), Horsham (Richmond Road), Horsham (Park Terrace Gardens), Itchingfield, North Stoke, Nutbourne, Nuthurst, Pulborough (Church Place), Pulborough (Lower Street), Rudgwick, Rusper, Shipley, Slinfold, Steyning, Storrington, Sullington, Thakeham, Upper Beeding (High Street), Upper Beeding (Hyde Street), Warnham, Washington, Watersfield, West Chiltington, West Chiltington Lanes, West Grinstead, Wiggonholt.

Seventeen of them have adopted character statements, which are worth reading if yours is one — they describe what the council considers worth protecting, and that is effectively the test your application will be judged against.

The council publishes the maps and character statements, and there is a mapping tool that will show you the boundary against your address. Boundaries are not intuitive: they follow historic plot patterns, not roads, and one side of a street is often in while the other is out.

What you lose inside one

A conservation area is “article 2(3) land” under the planning legislation. That designation strips out specific permitted development rights. The ones that matter for a house:

No side extensions at all. Outside a conservation area you can build a single storey side extension under permitted development, up to half the width of the original house. Inside one, that right is removed entirely. Any side extension needs a full planning application.

No two-storey rear extensions. Multi-storey rear extensions are not permitted development on article 2(3) land, full stop.

No permitted development loft conversion. This is the one that surprises people most. Class B — the right that lets you add a rear dormer within a volume allowance — is not available on article 2(3) land at any size. Every dormer in a conservation area needs planning permission.

No cladding. Cladding the exterior with stone, timber, render, tiles or plastic is not permitted development.

The larger home extension scheme is unavailable. The prior approval route that allows a single storey rear extension up to 8 metres (detached) or 6 metres (everything else) explicitly excludes article 2(3) land. You are back to the standard 4 metre and 3 metre limits, and anything beyond needs a full application.

What else needs permission that would not elsewhere

Horsham District Council’s own list of works requiring permission inside a conservation area includes:

• Adding an extension
• Altering the roof
• Cladding
• Constructing an outbuilding
• Altering windows and external doors
• Adding solar panels
• Satellite dishes
• Changing a fence, wall or gate facing a highway

That windows and doors line catches a lot of people. Replacing timber sash windows with uPVC in a conservation area is not a like-for-like repair in planning terms, and doing it without consent can attract enforcement.

The trees, which almost nobody knows about

Every tree in a conservation area with a trunk more than 75mm in diameter, measured 1.5m above the ground, is protected. You must give the council written notice six weeks before doing any work to one — including a tree in your own garden, and including work that seems minor.

That is a low threshold. A 75mm trunk is a young tree, not a veteran oak.

Applications for work to protected trees are free, so there is no reason not to do it properly. Unauthorised work to a tree covered by a Tree Preservation Order is a criminal offence, and “I did not know it was protected” is not a defence.

If you are extending anywhere near a tree, deal with this at design stage. It also affects your foundations — building near a mature tree on the clay soils common around Horsham usually means deeper foundations, which is a cost, not just a permission.

What this means in practice

Being in a conservation area does not mean you cannot extend. It means the route changes: instead of building under permitted development, you make a householder planning application, currently £548, with a statutory eight week determination period.

It also means the design is judged on whether it preserves or enhances the character of the area, which in practice means the council will have a view on materials, window proportions, roof form and how visible the work is from the street. Rear extensions that cannot be seen from anywhere public tend to be far less contentious than anything at the front.

Two things worth doing before you spend money on drawings

Check the boundary properly. Use the council’s mapping tool against your actual address rather than assuming from your street.

Consider paying for pre-application advice. Horsham District Council charges £105 for written advice on extensions and alterations to a house, with a 28-day response, or £65 for the simpler “do I need planning permission?” question. On a project where the answer changes your design, that is the cheapest money you will spend.

One more thing to check

If your property is in the south of the district, it may be inside the South Downs National Park — in which case your application is decided by the South Downs National Park Authority, not by Horsham District Council. Different authority, different portal, different policies. Parts of the north and east of the district fall within the High Weald National Landscape instead. Both are also article 2(3) land, so the restrictions above apply there too.

What to do next

If you are not sure which designations apply to your address, that is worth establishing before anything else — it determines both what you can build and who decides.

Tell us where the property is and we will tell you what you are dealing with.