Two-storey extensions for semi-detached houses in Dumfries

Quick reference for homeowners in Dumfries.

Postcode districts: DG1 and DG2
County / area: Dumfries and Galloway, Scotland
Price region: Scotland
Guide price: £52,500–£71,000 (£1,880–£2,540 per m²)
Approval route: Planning permission is usually needed: Class 1B permitted development only applies if every part of the extension is at least 10 m from all boundaries. A building warrant is needed before work starts.
Nearest towns: Locharbriggs (2.6 miles), Lockerbie (10.7 miles), Dalbeattie (12.6 miles)
First visit: Free, no obligation

About a two-storey extension for a semi-detached house

A two-storey extension for a semi-detached house is a two-floor addition to the rear, the open side, or both, designed around the attached neighbour on one side. The rear is often the simplest option and can sometimes be permitted development, while a side extension uses the gap on the detached side. Both need care with the shared party wall and the neighbour's light.

Around Dumfries we also work in Locharbriggs, Lockerbie and Dalbeattie, and across the rest of Dumfries and Galloway. Postcode districts in and near Dumfries: DG1 and DG2.

What it costs in Dumfries

Using our Scotland rates, a two-storey extension for a semi-detached house with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £52,500–£71,000, including VAT. Bigger or more glazed designs cost more per m². We'll give you a written design-stage price first, then a fixed build price once the drawings are agreed.

Spec	Per m²	A 4 m × 3.5 m footprint on two floors (28 m² of new floor space)
Essential	£1,730–£2,330 per m²	£48,500–£65,500
Standard	£1,880–£2,540 per m²	£52,500–£71,000
Premium	£2,260–£3,050 per m²	£63,000–£85,500

Planning and building standards in Dumfries

In Scotland, Class 1B permitted development needs a two-storey extension to be at least 10 m from every boundary, which a semi-detached house cannot meet on the attached side. In practice a two-storey extension to a semi needs a householder application, which costs £371 and is decided within two months, followed by a building warrant.

Approval in Scotland: Householder planning application: £371. Councils have two months to decide a local planning application.

Building standards: A building warrant from the council's building standards service before work starts, and a completion certificate at the end. Scotland uses its own Technical Handbooks.

Design points for Dumfries homes

The attached neighbour's light

A two-storey rear extension next to the party wall can take light from the neighbour's rear windows. Councils often use a 45-degree test, so the first floor may need to be shorter than the ground floor or set in from the shared boundary.

Keeping the pair balanced

Semis are designed as matching pairs, and a side extension changes that balance. Setting the side extension back from the front wall and keeping its ridge lower helps the pair still read as a pair, which councils' design guides commonly ask for.

How we'd run your project

Measure and listen
A visit to Dumfries 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.
Engineer it
Foundations sized for two floors, steels for any openings, and a building warrant, all before anyone starts on site.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

Questions about two-storey extensions for semi-detached houses in Dumfries

Who handles building standards for a project in Dumfries?

We handle it as part of the project. What's needed in Scotland: a building warrant from the council's building standards service before work starts, and a completion certificate at the end. Scotland uses its own Technical Handbooks. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.

How long does a two-storey extension for a semi-detached house take?

Allow 4 to 8 weeks for survey and design, then the approval period (councils have two months to decide a local planning application), 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.

Which postcodes do you cover around Dumfries?

We cover Dumfries (DG1 and DG2) and nearby places including Locharbriggs, Lockerbie and Dalbeattie, plus the rest of Dumfries and Galloway. The first site visit is free.

Does a two-storey extension add value to a semi-detached house?

It usually adds value, but the gain is never certain. Nationwide's 2025 research found that 10% more floor area was linked to about 5% higher value, and that adding a double bedroom and bathroom to a three-bed, one-bathroom house could add up to 24%. Every street has a ceiling price, so check local sales first.

What if my neighbour has already extended?

That often helps. An existing extension next door can reduce the effect of yours on their light, and may show what the council accepts on your street. It can also mean building alongside their wall, so we check its position, foundations and any windows facing your plot at the survey.

Nearby

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

Other extensions in Dumfries

All two-storey extension services in Dumfries · Two-storey extensions for semi-detached houses across Dumfries and Galloway

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