Two-storey extensions for semi-detached houses in Renfrew

Renfrew: the key facts for this kind of project.

Postcode districts: PA4
County / area: Renfrewshire and Inverclyde, 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: Clydebank (2.1 miles), Erskine (3 miles), Dalmuir (3 miles)
Distance to Paisley: about 3.2 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.

Renfrew sits about 3.2 miles from Paisley. Closer to home, Clydebank is 2.1 miles away and Erskine 3.0 miles.

What it costs in Renfrew

A guide price for Renfrew: around £52,500–£71,000 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). That works out at £1,880–£2,540 per m² of new floor space, including VAT at 20%. 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 Renfrew

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 Renfrew homes

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.

Rear, side or both

On a semi, a rear extension sits against the attached neighbour, while a side extension faces the detached neighbour and the street. We compare the space, cost and approval route for each, and for a wraparound, before you commit to one design.

How we'd run your project

Measure and listen
A visit to Renfrew to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
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.
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 Renfrew

Which postcodes do you cover around Renfrew?

We cover Renfrew (PA4) and nearby places including Clydebank, Erskine and Dalmuir, plus the rest of Renfrewshire and Inverclyde. The first site visit is free.

How much does a two-storey extension for a semi-detached house cost in Renfrew?

Our guide for Scotland, which covers Renfrew, 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.

Who handles building standards for a project in Renfrew?

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.

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.

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

Nearby towns we cover for two-storey extensions for semi-detached houses:

Other extensions in Renfrew

All two-storey extension services in Renfrew · Two-storey extensions for semi-detached houses across Renfrewshire and Inverclyde

Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.