Home extensions in Horsham
Every type of house extension in Horsham, from single-storey kitchen extensions to two-storey additions, side returns and orangeries. We design, handle the approvals and build.
- Postcode districtsRH12, RH13
- Price regionSouth East England (×1.12)
- Planning rulesEngland
- Site visitFree, no obligation
Planning and building control in Horsham
In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
In England a two-storey rear extension is permitted development only if it projects no more than 3 m from the original rear wall, sits at least 7 m from the rear boundary, matches the roof pitch and uses obscure, non-opening side windows upstairs. Most two-storey extensions therefore go through a householder planning application, which costs £548 from 1 April 2026 and normally takes about 8 weeks.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Applications are decided by the local planning authority (your district, borough or unitary council).
Which extension suits a Horsham home?
Homes across the South East range from Victorian terraces in the older town centres to large detached houses on the edges, so the right extension type varies street by street.
The types we would usually look at first for a home in Horsham are wraparound extensions, single-storey rear extensions and double-storey extensions, depending on the garden and how the house is laid out.
Guide prices for Horsham
Use these Horsham guide prices to sense-check a budget; the guide-price tool narrows them to your own size, and the site visit turns them into a written figure.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Orangery extensions | 16 m² | £50,000 – £63,000 |
| Single-storey rear extensions | 20 m² | £45,500 – £58,500 |
| Wraparound extensions | 25 m² | £64,000 – £81,500 |
| Conservatory replacement extensions | 14 m² | £33,500 – £43,500 |
| Kitchen extensions | 20 m² | £47,000 – £59,500 |
| Double-storey extensions | 32 m² | £64,500 – £84,500 |
| Side return extensions | 11 m² | £29,500 – £37,000 |
Horsham and surrounding towns
Across RH12, RH13, we can visit, measure and advise. Nearby, we also take on projects in Crawley (7 miles), Haywards Heath (11 miles), Burgess Hill (11 miles), East Grinstead (15 miles), Shoreham-by-Sea (16 miles). For homes towards Surrey, Horley is around 11 miles away.
Every extension type in Horsham
- Double-storey extensions · from £42,500
- Orangery extensions · from £33,500
- Side extensions · from £24,500
- Extension plans and drawings · from £1,300
- Single-storey rear extensions · from £23,500
- Utility and boot room extensions · from £15,500
- Wraparound extensions · from £40,000
- Bedroom extensions · from £29,000
- Building regulations for extensions · from £1,000
- Home office extensions · from £17,500
- Pitched roof extensions · from £24,500
- Bungalow extensions · from £29,000
- Glass box extensions · from £33,500
- Porch extensions · from £4,450
- Flat roof extensions · from £23,500
- Kitchen extensions · from £30,000
- Extensions over a garage · from £26,500
- Timber frame extensions · from £23,500
- Annexe extensions · from £61,500
- Conservatory replacement extensions · from £22,000
- Planning permission for extensions · from £350
- Side return extensions · from £20,000
Free site visit
It starts with a visit to your house to measure, check access and talk through ideas and budget.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Questions about extensions in Horsham
How much does an extension cost in Horsham?
Using our South East England factor (×1.12), a standard-spec single-storey extension of 20 m² is a guide £45,500 to £58,500 including VAT, and a 32 m² two-storey extension £64,500 to £84,500. Your written price follows the survey.
Who do I contract with?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Do you cover all of Horsham?
Yes, including the surrounding parts of West Sussex. Site visits are free and there is no obligation.
Do I need planning permission for an extension in Horsham?
Not always. It depends on the size, position and your property's history. Many single-storey rear extensions in England are permitted development or can use prior approval.
Will my neighbours need to be told?
If you apply for planning or prior approval the council notifies them, and in England party wall notices may be needed for work near a shared boundary.
Book a free site visit in Horsham
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.