Two-storey extensions for semi-detached houses in Thurso
Homes in Thurso with a bit of space to the side or rear can often take a two-storey extension for a semi-detached house. We'll tell you honestly whether yours can, and what approvals it needs.
We take on projects in Thurso by arrangement. Site visits here aren't free as standard, and we'll agree travel costs with you in writing first.
Thurso: the key facts for this kind of project.
- Postcode districts
- KW12 and KW14
- County / area
- The Highlands, Moray and Islands, 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
- Wick (18.9 miles), Tain (57.3 miles), Lossiemouth (60.9 miles)
- Distance to Inverness
- about 81.1 miles
- First visit
- By arrangement
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 Thurso we also work in Wick, Tain and Lossiemouth, and across the rest of the Highlands, Moray and Islands. Postcode districts in and near Thurso: KW12 and KW14.
What it costs in Thurso
Expect a two-storey extension for a semi-detached house in Thurso to land somewhere around £52,500–£71,000 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Our Scotland guide rate is £1,880–£2,540 per m², including VAT. Professional fees for drawings and the structural engineer are listed separately on our prices page.
| 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 Thurso
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 Thurso 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
Visit by arrangement
We agree a visit to your home in Thurso and any travel costs with you in writing first, then look at the structure, access and boundaries.
Design and approvals
We draw the extension and check it against the rules for Scotland, then apply for planning permission or a certificate of lawfulness, whichever fits.
Detail and price
Construction drawings, engineer's calculations and building warrant approval, then a written fixed price for the build.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the completion certificate at the end.
Questions about two-storey extensions for semi-detached houses in Thurso
Who handles building standards for a project in Thurso?
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.
Do I need planning permission for a two-storey extension for a semi-detached house in Thurso?
Thurso is in Scotland. 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.
How much does a two-storey extension for a semi-detached house cost in Thurso?
Our guide for Scotland, which covers Thurso, is £1,880–£2,540 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £52,500–£71,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Will a side extension make my semi look like a terrace?
It can if it fills the whole gap to the boundary at first floor and the neighbour does the same. Many councils ask for a first-floor gap to the side boundary or a set-back for this reason. We design the extension to keep the semi reading as one of a pair.
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.
Nearby
We also cover places near Thurso, including:
Other extensions in Thurso
- Rear
- Side
- Wraparound
- Part two-storey
- Over a garage
- First floor
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Thurso · Two-storey extensions for semi-detached houses across the Highlands, Moray and Islands
Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.