Horsham, West Sussex
Single-storey rear extension in Horsham
Ground-floor space across the back of the house, usually for a kitchen, dining or family room. We design, get the approvals for and build single-storey rear extensions in Horsham and the surrounding area, with one contract from the first survey to building control sign-off.
Horsham is covered from our West Sussex round, including RH12. A depth of 3 to 4 metres keeps many single-storey rear extensions in Horsham within permitted development, subject to the house's planning history.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a single-storey rear extension cost in Horsham?
For Horsham we work from the South East England rate: £2,130–£3,470 per square metre of new floor, including VAT, standard specification. South East prices run above our West Midlands baseline, mainly on labour rates and clay-soil foundations.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £25,500–£41,500 |
| 4 m wide × 5 m deep (20 m²) | £42,500–£69,500 |
| 4 m wide × 6 m deep (24 m²) | £51,000–£83,500 |
Ground conditions, glazing, the roof and how far the house is opened up move the final figure within the range.
Do you need planning permission for a single-storey rear extension in Horsham?
Here is how the rules in England apply to a single-storey rear extension in Horsham.
In England a single-storey rear extension can often be built under permitted development: up to 3 metres beyond the original rear wall of an attached house, or 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres if any part is within 2 metres of a boundary.
England also has the larger home extension route: a single-storey rear extension of up to 6 metres on an attached house or 8 metres on a detached house, after prior approval from the council. The council notifies your neighbours and has 42 days to decide; the fee is £249 (£310 for applications made from 8 December 2026). The route is not available on designated land such as conservation areas.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. At the first visit we measure what is there now and tell you which route fits: permitted development, prior approval or a planning application.
What are homes in Horsham like to extend?
Horsham has a mix of Victorian terraces near the centre and larger Edwardian and inter-war houses further out. Clay soils across much of the South East mean deeper foundations near trees, which we plan for at the survey.
How a single-storey rear extension in Horsham comes together
Free site visit
We measure the house and garden, look at the back wall, drainage and boundaries, and talk through what you want from the space.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
Paperwork handled
Planning, prior approval or permitted development, Building Regulations approval, structural design and party wall notices are all handled by us.
Written price, then build
Once the design and approvals are in place, you get a fixed written price and programme, and we build through to sign-off.
Single-storey rear extensions near Horsham
We also build single-storey rear extensions in nearby Broadfield (5.8 miles) and Crawley (7.2 miles).
- Single-storey rear extension in Broadfield
- Single-storey rear extension in Crawley
- Single-storey rear extension in Cranleigh
- Single-storey rear extension in Horley
- Single-storey rear extension in Hurstpierpoint
Other work in Horsham:
FAQ
Single-storey rear extension questions in Horsham
Do you handle building control in Horsham?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.
Is the site visit in Horsham free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
Do I need a structural engineer?
Yes for the beam over the new opening and usually for the foundations. Their calculations go to building control with the drawings.
How long does a rear extension take to build in Horsham?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
Do I need a party wall agreement?
In England, usually yes if the extension is on or near a shared boundary or the foundations are close to a neighbour's building. We serve the notices.
Will I need a structural engineer?
Yes for the beam over the new opening and usually the foundations; we arrange them and their calculations go to building control.