First-floor extensions in Midsomer Norton

What we'd confirm first for a project in Midsomer Norton.

Postcode districts: BA3 and BS39
County / area: Somerset, England
Price region: South West England
Guide price: £26,000–£37,500 (£1,850–£2,680 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: Publow (6.9 miles), Shepton Mallet (7.1 miles), Chew Magna (7.7 miles)
Distance to Bath: about 8.2 miles
First visit: Free, no obligation

About a first-floor extension

A first-floor extension is a new upstairs room built on top of an existing single-storey part of your house, such as a rear kitchen extension, a utility or a side annexe. It adds a bedroom, bathroom or study without enlarging the footprint. Whether it works depends mainly on whether the walls and foundations below can carry the extra load.

Around Midsomer Norton we also work in Publow, Shepton Mallet and Chew Magna, and across the rest of Somerset. Postcode districts in and near Midsomer Norton: BA3 and BS39.

What it costs in Midsomer Norton

Using our South West England rates, a first-floor extension with 4 m × 3.5 m of new first-floor space (14 m²) comes to about £26,000–£37,500, including VAT. Bigger or more glazed designs cost more per m². 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	£1,710–£2,460 per m²	£24,000–£34,500
Standard	£1,850–£2,680 per m²	£26,000–£37,500
Premium	£2,220–£3,210 per m²	£31,000–£45,000

Planning and building regulations in Midsomer Norton

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 Midsomer Norton 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

Understand the brief
At your home in Midsomer Norton we agree what you need: bedroom count, bathroom, kitchen space, and how much garden you want to keep.
Get it approved
Once you're happy with the design we submit it to the council for Midsomer Norton and deal with any questions from the planning officer.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.

Questions about first-floor extensions in Midsomer Norton

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.

Do I need planning permission for a first-floor extension in Midsomer Norton?

Midsomer Norton is in England, so England planning rules apply. 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. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.

Which postcodes do you cover around Midsomer Norton?

We cover Midsomer Norton (BA3 and BS39) and nearby places including Publow, Shepton Mallet and Chew Magna, plus the rest of Somerset. The first site visit is free.

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

We also cover places near Midsomer Norton, including:

Other extensions in Midsomer Norton

All two-storey extension services in Midsomer Norton · First-floor extensions across Somerset

Tell us about your house in Midsomer Norton and we'll call you back to arrange a free, no-obligation visit.