Two-storey extensions for detached houses in Brackley

Before you start in Brackley, here's what applies.

Postcode districts: NN13
County / area: Northamptonshire, England
Price region: East Midlands
Guide price: £84,500–£113,000 (£2,010–£2,700 per m²)
Approval route: Depends on position: a two-storey rear extension may be permitted development (3 m deep, 7 m from the rear boundary); a two-storey side extension needs planning permission.
Nearest towns: Buckingham (7.3 miles), Banbury (8.4 miles), Bicester (9.2 miles)
Distance to Northampton: about 18.8 miles
First visit: Free, no obligation

About a two-storey extension for a detached house

This service suits you if you own a detached house and want a substantial amount of extra space, whether a side extension over a drive, a rear extension into the garden or a wraparound. You get a survey of the whole plot, options that compare layouts and costs, the approvals your nation needs, structural design and the build, carried out by vetted teams working under S&K.

Around Brackley we also work in Buckingham, Banbury and Bicester, and across the rest of Northamptonshire. Postcode district in and near Brackley: NN13.

What it costs in Brackley

A guide price for Brackley: around £84,500–£113,000 for a 3 m × 7 m footprint on two floors (42 m² of new floor space). That works out at £2,010–£2,700 per m² of new floor space, including VAT at 20%. The fastest way to a firmer number is a free site visit, after which we price the design stage in writing.

Spec	Per m²	A 3 m × 7 m footprint on two floors (42 m² of new floor space)
Essential	£1,850–£2,480 per m²	£77,500–£104,000
Standard	£2,010–£2,700 per m²	£84,500–£113,000
Premium	£2,410–£3,230 per m²	£101,500–£136,000

Planning and building regulations in Brackley

In England, a two-storey rear extension on a detached house can be permitted development within 3 m of the original rear wall and at least 7 m from the rear boundary, with matching roof pitch and materials, outside protected areas. Any two-storey side or wraparound extension needs planning permission, costing £548 (or £575 for applications made from 8 December 2026), with a decision due within 8 weeks of validation.

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 Brackley homes

Keeping it subordinate

Large detached houses can take a large extension, but councils still expect it to look secondary to the main house. A lower ridge, a modest set-back at the front and matching materials keep the proportions right, even on a wide plot.

Larger spans and steelwork

Bigger extensions often mean wider openings and longer spans, which need more steel and sometimes a steel frame. The engineer designs these early, because the size of the steel affects ceiling heights, floor depths and the cost.

How we'd run your project

Understand the brief
At your home in Brackley we agree what you need: bedroom count, bathroom, kitchen space, and how much garden you want to keep.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering Brackley.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.

Questions about two-storey extensions for detached houses in Brackley

Who handles building regulations for a project in Brackley?

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 Brackley?

We cover Brackley (NN13) and nearby places including Buckingham, Banbury and Bicester, plus the rest of Northamptonshire. The first site visit is free.

How long does a two-storey extension for a detached house 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.

Can I extend a detached house on both sides?

Sometimes. With planning permission, a council may accept extensions on both sides if the house stays well proportioned and keeps gaps to the boundaries. It is more common to extend on one side and the rear, or with a wraparound. We look at the plot as a whole before suggesting more than one extension.

Is a detached house extension a better investment than moving?

It often costs less than the gap between your house and a larger one nearby, once property tax, legal fees and removal costs are counted, but that depends on your area. Extending also has limits: every street has a ceiling price. We give you build costs so you can compare them with local asking prices.

Nearby

Close to Brackley? We work across the area, including:

Other extensions in Brackley

All two-storey extension services in Brackley · Two-storey extensions for detached houses across Northamptonshire

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