Two-storey side extensions in Amersham

Quick reference for homeowners in Amersham.

Postcode districts: HP7 and HP16
County / area: Buckinghamshire, England
Price region: South East England
Guide price: £94,500–£127,000 (£2,260–£3,030 per m²)
Approval route: Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
Nearest towns: Amersham on the Hill (0.7 miles), Chesham (2.4 miles), Beaconsfield (4 miles)
Distance to Milton Keynes: about 26.6 miles
First visit: Free, no obligation

About a two-storey side extension

A two-storey side extension is a new two-floor addition built into the space beside your house, often over a driveway or side passage. It typically adds one or two bedrooms upstairs and a utility, study or larger kitchen below, without giving up rear garden.

We cover postcode districts HP7 and HP16 in and around Amersham, along with neighbouring Amersham on the Hill, Chesham and Beaconsfield.

What it costs in Amersham

Our guide for South East England is £2,260–£3,030 per m² including VAT. On a project with a 3 m × 7 m footprint on two floors (42 m² of new floor space), that puts a two-storey side extension in Amersham at roughly £94,500–£127,000. We'll give you a written design-stage price first, then a fixed build price once the drawings are agreed.

Spec	Per m²	A 3 m × 7 m footprint on two floors (42 m² of new floor space)
Essential	£2,070–£2,780 per m²	£87,000–£117,000
Standard	£2,260–£3,030 per m²	£94,500–£127,000
Premium	£2,710–£3,630 per m²	£113,500–£152,500

Planning and building regulations in Amersham

In England, a two-storey side extension always needs householder planning permission, because permitted development only allows single-storey extensions beyond a side wall. The fee is £548 (or £575 for applications made from 8 December 2026), and councils should decide within 8 weeks of validation. Expect them to look at set-back, roof height, gaps to the boundary and the effect on neighbours.

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 Amersham homes

Access and services

Side extensions often cover the only route to the back garden, a gas meter, soil pipes or a drain run. We plan bin and bike access, move meters and pipes where needed and check drains early, because these items affect both cost and layout.

Side windows, boundaries and gutters

Upstairs windows in the side wall face the neighbour, so they are usually obscure-glazed and fixed, or left out. Building close to the boundary also raises questions about foundations, overhanging gutters and access for maintenance, so we design the eaves and gutter to stay within your land.

How we'd run your project

Measure and listen
A visit to Amersham to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Plans, then approval
Measured survey, design, then the right approval route for your house. We explain each step before we take it.
Price it properly
Once the engineer's calculations are in, we fix the build price in writing, with a clear list of what's included.
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 two-storey side extensions in Amersham

How long does a two-storey side 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.

Do I need planning permission for a two-storey side extension in Amersham?

Amersham is in England, so England planning rules apply. Planning permission is needed: in England, permitted development only allows single-storey extensions to the side. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.

How much does a two-storey side extension cost in Amersham?

Our guide for South East England, which covers Amersham, is £2,260–£3,030 per m² including VAT. A typical project with a 3 m × 7 m footprint on two floors (42 m² of new floor space) comes to about £94,500–£127,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Who handles building regulations for a project in Amersham?

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.

Can I build a two-storey side extension over my driveway?

Yes, if the drive is wide enough for a useful room and the council accepts the design. You may lose off-road parking, which some councils weigh up, and the foundations need to suit the ground below. We check parking, drains and meter positions at the free site visit before any drawings are prepared.

Nearby

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

Other extensions in Amersham

All two-storey extension services in Amersham · Two-storey side extensions across Buckinghamshire

The quickest next step is a visit. We'll look at your house in Amersham and give you an honest view of the options.