Two-storey rear extensions in Dumbarton

Quick reference for homeowners in Dumbarton.

Postcode districts: G82
County / area: Glasgow and Dunbartonshire, 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: Vale of Leven (1.9 miles), Bonhill (2.4 miles), Alexandria (3.5 miles)
Distance to Glasgow: about 13.3 miles
First visit: Free, no obligation

About a two-storey rear extension

A two-storey rear extension is a new two-floor addition built onto the back of your house, usually giving a larger kitchen or living space on the ground floor and one or two bedrooms or a bathroom above. Because both floors share one set of foundations and one roof, it adds a lot of floor space for the garden it uses. In some cases it can be built under permitted development, depending on where you live.

Around Dumbarton we also work in Vale of Leven, Bonhill and Alexandria, and across the rest of Glasgow and Dunbartonshire. Postcode district in and near Dumbarton: G82.

What it costs in Dumbarton

Most of the cost of a two-storey rear extension is set by its size and specification. For Dumbarton and the rest of Scotland, our guide is £1,880–£2,540 per m² including VAT, so about £52,500–£71,000 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). The fastest way to a firmer number is a free site visit, after which we price the design stage in writing.

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 Dumbarton

In Scotland, a two-storey rear extension is only permitted development under Class 1B if no part of it is within 10 m of any boundary, it is no higher than the house and the house is not in a conservation area. Most gardens cannot meet the 10 m test, so expect a householder application (£371, decided within two months) and a building warrant before work starts.

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 Dumbarton homes

Opening up the ground floor

Knocking through the old rear wall means steel beams to carry the first floor and roof above. The structural engineer sets the beam sizes, padstones and any posts, and we plan them early so the open-plan layout you want is the one that gets built.

Depth and neighbours' light

Councils check that a two-storey rear extension does not take too much light or outlook from neighbouring windows, and many use a 45-degree line drawn from the nearest habitable window. We test this at sketch stage, so the depth you are shown is one that can realistically be approved.

How we'd run your project

Look at the house
We start in Dumbarton with a free visit: measurements, photos, a look at the loft and drains, and a frank chat about budget.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering Dumbarton.
Detail and price
Construction drawings, engineer's calculations and building warrant approval, then a written fixed price for the build.
Finish and certify
Second fix, plastering and making good, then the council's final building standards inspection and the completion paperwork.

Questions about two-storey rear extensions in Dumbarton

How much does a two-storey rear extension cost in Dumbarton?

Our guide for Scotland, which covers Dumbarton, 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.

Which postcodes do you cover around Dumbarton?

We cover Dumbarton (G82) and nearby places including Vale of Leven, Bonhill and Alexandria, plus the rest of Glasgow and Dunbartonshire. The first site visit is free.

How long does a two-storey rear extension 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.

Do I need planning permission for a two-storey rear extension in Dumbarton?

Dumbarton 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.

Will a two-storey rear extension block my neighbour's light?

It can if it is too deep or too close to the boundary, which is why councils look closely at its effect on neighbouring windows and gardens. We test the design against light and outlook early, keep the first floor shorter or set in where needed, and use a hipped roof to reduce bulk on the boundary side.

Nearby

Nearby towns we cover for two-storey rear extensions:

Other extensions in Dumbarton

All two-storey extension services in Dumbarton · Two-storey rear extensions across Glasgow and Dunbartonshire

Book a free site visit in Dumbarton and we'll tell you what's possible, what approvals you need and what the design stage would cost.