First-floor extensions in Chesterfield

Useful details for planning a first-floor extension in Chesterfield.

Postcode districts: S40, S41 and S42
County / area: Derbyshire, England
Price region: East Midlands
Guide price: £24,500–£35,500 (£1,760–£2,550 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: Staveley (3 miles), Dronfield (4.3 miles), Bolsover (5.4 miles)
Distance to Derby: about 22.7 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 Chesterfield (S40, S41 and S42) and the places around it, including Staveley (3.0 miles), Dronfield (4.3 miles) and Bolsover.

What it costs in Chesterfield

Expect a first-floor extension in Chesterfield to land somewhere around £24,500–£35,500 for 4 m × 3.5 m of new first-floor space (14 m²). Our East Midlands guide rate is £1,760–£2,550 per m², including VAT. These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.

Spec	Per m²	4 m × 3.5 m of new first-floor space (14 m²)
Essential	£1,620–£2,340 per m²	£22,500–£33,000
Standard	£1,760–£2,550 per m²	£24,500–£35,500
Premium	£2,120–£3,060 per m²	£29,500–£43,000

Planning and building regulations in Chesterfield

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 Chesterfield homes

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.

Can the existing structure take it?

Many single-storey extensions were built with foundations, walls and lintels sized for one storey. We find out what is there with trial holes and, where available, the original building control drawings. The engineer then decides whether to reuse, strengthen or rebuild parts of the structure.

How we'd run your project

Visit and first ideas
One of our team visits your house in Chesterfield, checks the walls, roof and drains, and sketches out options with you.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
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 Chesterfield

How long does a first-floor extension take?

Allow 4 to 8 weeks for survey and design, then the approval period (councils should decide householder applications within 8 weeks of validation), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.

How much does a first-floor extension cost in Chesterfield?

Our guide for the East Midlands, which covers Chesterfield, is £1,760–£2,550 per m² including VAT. A typical project with 4 m × 3.5 m of new first-floor space (14 m²) comes to about £24,500–£35,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Which postcodes do you cover around Chesterfield?

We cover Chesterfield (S40, S41 and S42) and nearby places including Staveley, Dronfield and Bolsover, plus the rest of Derbyshire. The first site visit is free.

What happens to the room below while the first floor is built?

The old roof is removed, so the room below is exposed for a short period. We fit temporary weather protection, plan the work so the roof comes off only when the new structure is ready, and agree with you which rooms will be out of use and for roughly how long.

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

The same service in neighbouring towns:

Other extensions in Chesterfield

All two-storey extension services in Chesterfield · First-floor extensions across Derbyshire

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