First-floor extensions in Burgess Hill

The basics for Burgess Hill at a glance.

Postcode districts: RH15
County / area: West Sussex, England
Price region: South East England
Guide price: £27,500–£40,000 (£1,980–£2,860 per m²)
Approval route: It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission.
Nearest towns: Hurstpierpoint (2.7 miles), Haywards Heath (3 miles), Lewes (8.5 miles)
Distance to Crawley: about 10.9 miles
First visit: Free, no obligation

About a first-floor extension

A first-floor extension suits you if your house already has a single-storey extension and you need more space upstairs. You get a structural check of the existing walls and foundations, a design that ties the new floor into the house, the approvals your nation needs, building regulations approval and the build, managed by us and carried out by vetted teams working under S&K.

We cover Burgess Hill (RH15) and the places around it, including Hurstpierpoint (2.7 miles), Haywards Heath (3.0 miles) and Lewes.

What it costs in Burgess Hill

For budgeting in Burgess Hill, allow around £27,500–£40,000 for a first-floor extension with 4 m × 3.5 m of new first-floor space (14 m²). That's based on £1,980–£2,860 per m² including VAT for South East England. Kitchens, bathroom fittings and flooring are priced separately so you can compare like with like.

Spec	Per m²	4 m × 3.5 m of new first-floor space (14 m²)
Essential	£1,820–£2,630 per m²	£25,500–£37,000
Standard	£1,980–£2,860 per m²	£27,500–£40,000
Premium	£2,380–£3,430 per m²	£33,500–£48,000

Planning and building regulations in Burgess Hill

In England, adding a first floor turns a single-storey extension into one of more than one storey. To be permitted development, the extension as a whole must go no more than 3 m beyond the rear wall of the original house and stay at least 7 m from the rear boundary, with matching materials and roof pitch. Over a side extension it always needs planning permission, costing £548 (or £575 for applications made from 8 December 2026).

Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.

Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.

Design points for Burgess Hill homes

Escape and fire safety

A new first-floor bedroom needs an escape window with a clear opening of at least 0.33 m², at least 450 mm wide and 450 mm high, with the bottom no more than 1,100 mm above the floor, unless there is a protected route to the stairs.

Replacing the flat roof

The existing roof usually comes off and is replaced by a new first-floor structure. The room below is exposed for a short time, so we plan temporary weatherproofing and sequence the work to keep the kitchen or living room usable for as long as possible.

How we'd run your project

Measure and listen
A visit to Burgess Hill to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering Burgess Hill.
Structure and building control
A structural engineer sizes the foundations and steels, and we get building regulations approval before work starts.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the building control completion certificate at the end.

Questions about first-floor extensions in Burgess Hill

Who handles building regulations for a project in Burgess Hill?

We handle it as part of the project. What's needed in England: building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.

Which postcodes do you cover around Burgess Hill?

We cover Burgess Hill (RH15) and nearby places including Hurstpierpoint, Haywards Heath and Lewes, plus the rest of West Sussex. The first site visit is free.

How much does a first-floor extension cost in Burgess Hill?

Our guide for South East England, which covers Burgess Hill, is £1,980–£2,860 per m² including VAT. A typical project with 4 m × 3.5 m of new first-floor space (14 m²) comes to about £27,500–£40,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Can I build on top of my existing single-storey extension?

Often yes, but only after the structure has been checked. Foundations, walls and lintels built for one storey may not carry two. We dig trial holes, look for the original building control approval and ask the structural engineer to confirm what can stay, what needs strengthening and what must be rebuilt.

Will the first-floor extension match my house?

It should, and in England matching materials and roof pitch is a condition of permitted development. We match brick, tile, mortar colour and window style where we can, and tell you at the design stage if an exact brick match is not available, so you can choose between the closest match and render or cladding.

Nearby

Nearby towns we cover for first-floor extensions:

Other extensions in Burgess Hill

All two-storey extension services in Burgess Hill · First-floor extensions across West Sussex

Ready to talk it through? Call us or send the form and we'll arrange a visit to your home in Burgess Hill.