First-floor extensions in Alexandria
We cover Alexandria and the rest of Glasgow and Dunbartonshire for first-floor extensions. Start with a free site visit and a plain-English view of what your house and plot can take.
Useful details for planning a first-floor extension in Alexandria.
- Postcode districts
- G83
- County / area
- Glasgow and Dunbartonshire, Scotland
- Price region
- Scotland
- Guide price
- £23,500–£34,000 (£1,690–£2,440 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
- Bonhill (1.3 miles), Vale of Leven (1.6 miles), Dumbarton (3.5 miles)
- Distance to Glasgow
- about 15.5 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.
We cover Alexandria (G83) and the places around it, including Bonhill (1.3 miles), Vale of Leven (1.6 miles) and Dumbarton.
What it costs in Alexandria
Most of the cost of a first-floor extension is set by its size and specification. For Alexandria and the rest of Scotland, our guide is £1,690–£2,440 per m² including VAT, so about £23,500–£34,000 for 4 m × 3.5 m of new first-floor space (14 m²). We'll give you a written design-stage price first, then a fixed build price once the drawings are agreed.
| Spec | Per m² | 4 m × 3.5 m of new first-floor space (14 m²) |
|---|---|---|
| Essential | £1,560–£2,250 per m² | £22,000–£31,500 |
| Standard | £1,690–£2,440 per m² | £23,500–£34,000 |
| Premium | £2,030–£2,930 per m² | £28,500–£41,000 |
Planning and building standards in Alexandria
In Scotland, permitted development for extensions of more than one storey (Class 1B) needs at least 10 m to every boundary and no part higher than the house. Most first-floor extensions cannot meet the 10 m test, so plan for 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 Alexandria homes
Escape and fire safety
A new first-floor bedroom needs an escape window with a clear opening of at least 0.33 m², at least 450 mm wide and 450 mm high, with the bottom no more than 1,100 mm above the floor, unless there is a protected route to the stairs.
Tying into the house
The new floor and walls must line up with the existing first floor, often through a new opening in the rear wall above the old one. Floor levels, the position of upstairs windows and the existing roof all affect where the opening can go, so we survey both floors carefully.
How we'd run your project
Free site visit
We visit your home in Alexandria, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering Alexandria.
Structure and building standards
A structural engineer sizes the foundations and steels, and we get a building warrant before work starts.
Finish and certify
Second fix, plastering and making good, then the council's final building standards inspection and the completion paperwork.
Questions about first-floor extensions in Alexandria
Do I need planning permission for a first-floor extension in Alexandria?
Alexandria 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 first-floor extension cost in Alexandria?
Our guide for Scotland, which covers Alexandria, is £1,690–£2,440 per m² including VAT. A typical project with 4 m × 3.5 m of new first-floor space (14 m²) comes to about £23,500–£34,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
How long does a first-floor 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.
What happens to the room below while the first floor is built?
The old roof is removed, so the room below is exposed for a short period. We fit temporary weather protection, plan the work so the roof comes off only when the new structure is ready, and agree with you which rooms will be out of use and for roughly how long.
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 a building warrant and ask the structural engineer to confirm what can stay, what needs strengthening and what must be rebuilt.
Nearby
The same service in neighbouring towns:
Other extensions in Alexandria
- Rear
- Side
- Wraparound
- Part two-storey
- Over a garage
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Alexandria · First-floor extensions across Glasgow and Dunbartonshire
Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.