Who decides your planning application — Horsham council, or the National Park?

You pay council tax to Horsham District Council. It does not follow that Horsham District Council decides your planning application.

Parts of the district sit inside the South Downs National Park, and inside the Park boundary the local planning authority is the South Downs National Park Authority. Horsham District Council states this plainly: if your property is within the National Park, your application will be managed by the Park Authority.

Different authority. Different portal. Different policies. Different local plan.

Which parts of the district

The National Park covers the southern part of Horsham District — the downland side, taking in the area around Storrington, Amberley, Sullington and Washington. The boundary is drawn on landscape lines rather than parish boundaries, so a village can be partly in and partly out.

The only reliable way to know is to check your specific address against the boundary, not to reason from which village you are in.

The other designation, in the opposite corner

Parts of the north and east of the district fall within the High Weald National Landscape — still legally an Area of Outstanding Natural Beauty, and renamed rather than downgraded. Horsham District Council is one of fifteen partner authorities to its management plan.

The High Weald is not a separate planning authority. Applications there are still decided by Horsham District Council. But the designation carries real weight in policy terms, and it has the same effect on permitted development as the National Park does.

What both designations do to permitted development

The National Park and the High Weald are both article 2(3) land, exactly as conservation areas are. That means the same removals:

• No side extensions under permitted development
• No two-storey rear extensions
• No permitted development loft conversions — Class B is unavailable entirely
• No cladding
• The larger home extension scheme is unavailable, so rear extension depths are capped at 4 metres (detached) and 3 metres (everything else)

So the practical position for a property in the National Park is: fewer things you can do without permission, and a different authority to ask when you need it.

Why it matters beyond the address on the envelope

You will submit to the wrong place. Applications go through the South Downs portal, not Horsham’s. Submitting to the wrong authority wastes weeks.

The policies are different. The National Park Authority has its own local plan, with its own policies on design, landscape and dark skies. The Park has statutory purposes around conserving natural beauty which weigh heavily in decisions, and applications there routinely attract more scrutiny on materials, massing and external lighting than an equivalent proposal a few miles north.

Pre-application advice is a different service at a different price. Horsham District Council’s own charges — £65 for “do I need permission”, £105 for advice on extensions — apply to applications it determines. The Park Authority runs its own scheme.

Building control is unaffected. This is the bit that catches people out in the other direction. National Park status changes the planning authority; it does not change building control. Sussex Building Control, the shared service run by Horsham District Council and Crawley Borough Council, still handles building regulations for the district, National Park or not. Two different bodies for the two different processes.

And one thing that recently got simpler

For four years, development across the Sussex North water supply zone — much of this district — was held up by Natural England’s water neutrality position, requiring statements and offsetting payments.

That position was withdrawn on 31 October 2025. From 1 November 2025 no water neutrality statement is needed and no payment into the certification scheme is required. New dwellings still have to meet the tighter water efficiency standard of 110 litres per person per day under council policy.

A lot of what is written online about developing around Horsham still describes the old regime. If somebody quotes you for a water neutrality statement, it is out of date.

How to check

Use the council’s mapping tool, which carries the designation layers, and check your actual address rather than your village. If you are close to a boundary, that check is worth doing carefully — the difference is not a nuance, it is a different authority.

If you are inside the Park, go to the South Downs National Park Authority for planning and to Sussex Building Control for building regulations.

What to do next

Establishing which authority decides your application is the first thing to do, before drawings and well before a builder. It changes the process, the policies and the timescale.

Tell us the address and we will tell you which regime you are in.