Thinking about extending your home in Glasgow and want a straight answer on cost before you speak to anyone? This guide gives real 2026 prices for single-storey, double-storey and side extensions in Glasgow, what drives the price up or down, what the council needs from you, and how we price a build at Home Decor Zone. We build extensions across the southside and West End as a family-run team, since 2011.
What our prices include
All prices on this page are labour plus building materials — plaster, plasterboard, pipework and plumbing fittings, electrical cable and accessories, timber, plywood, adhesives, grout, sealants and fixings — and include VAT. Every quote is itemised line by line.
Not included (you buy these, or we can supply and add them to the quote): the extension itself is priced complete to a decorated, floored shell; a kitchen or bathroom fitted inside it is a separate quote (kitchen units and appliances £3,000–£12,000 plus fitting). You get our 10% trade discount at Topps Tiles, B&Q TradePoint, Wholesale Domestic and Victoria Plumbing.
House extension cost in Glasgow 2026: the short answer
A single-storey rear extension in Glasgow costs £2,200–£3,000 per square metre for a standard finish, so a typical 20 m² kitchen-diner extension lands at £45,000–£65,000 including VAT, drawings and the building warrant. Double-storey work costs less per square metre because the roof and foundations are shared, but more overall. Prices below are what our recent Glasgow jobs have actually cost, not national averages.
| Extension type (Glasgow, standard finish) | Typical cost inc. VAT |
|---|---|
| Single-storey rear extension, 15 m² (small kitchen extension) | £38,000 – £48,000 |
| Single-storey rear extension, 20 m² (kitchen-diner) | £45,000 – £65,000 |
| Single-storey rear extension, 30 m² (open-plan family room) | £62,000 – £85,000 |
| Side return extension (Victorian/Edwardian terrace) | £40,000 – £60,000 |
| Wrap-around (side + rear) | £75,000 – £110,000 |
| Double-storey rear extension, 2 × 20 m² | £85,000 – £120,000 |
| Garden room / detached outbuilding, 15–20 m² | £28,000 – £45,000 |
All figures include VAT, structural engineer’s calculations, drawings and building warrant fees. They assume a standard finish — plastered walls, painted, laminate or engineered-wood floor, standard bifold or French doors. A kitchen fitted inside the new space is priced separately; see our kitchen cost guide.
Where the money goes
For a 20 m² single-storey extension at around £55,000, the split is roughly:
| Item | Share of cost |
|---|---|
| Drawings, structural engineer, building warrant application | £3,500 – £5,000 |
| Groundworks, foundations, drainage | £7,000 – £10,000 |
| Blockwork walls, cavity insulation, lintels | £8,000 – £11,000 |
| Roof — flat (GRP/EPDM) or pitched with tiles | £6,000 – £10,000 |
| Windows, bifold or French doors, roof lights | £5,000 – £9,000 |
| First-fix electrics and plumbing, underfloor heating if wanted | £3,500 – £6,000 |
| Plastering, flooring, skirtings, decoration | £5,000 – £8,000 |
| Knock-through to existing house, steel beam, making good | £3,000 – £6,000 |
| Skip hire, scaffold, site set-up | £2,000 – £3,500 |
What makes a Glasgow extension cost more (or less)
- Ground conditions. Much of the southside sits on clay; parts of the West End have made ground. Deeper foundations add £2,000–£5,000. A quick trial hole before the quote avoids surprises.
- Drainage. If a shared sewer runs under the footprint, Scottish Water needs a build-over agreement and the design changes. Budget £1,500–£3,000 and 4–6 extra weeks.
- Sandstone villas and period houses. Matching stone or a rendered finish that suits the house costs more than facing brick; conservation areas (Pollokshields, Dowanhill, Park) may insist on it.
- Roof type. A warm flat roof with a roof lantern is cheaper than a pitched, tiled roof tied into the existing eaves.
- Glazing. Bifolds run £1,200–£2,000 per metre; French doors plus a window do the same job for half that.
- Kitchen inside the extension. The extension gives you the room; the kitchen fit-out is a second budget — typically £7,000–£15,000 for a standard Howdens or Wren kitchen fitted.
- Time of year. Groundworks in a wet Glasgow winter cost more in pumping, time and mud. Spring starts are cheaper.
Planning permission and building warrant in Glasgow
Most single-storey rear extensions up to 4 m deep (semi/terrace: 3 m) fall under permitted development in Scotland, so no planning application is needed — but a building warrant from Glasgow City Council is always required. Warrant fees are based on the value of works (around £600–£1,200 for a typical extension), the application takes 6–10 weeks, and you cannot legally start before it is granted. Conservation areas and flats are different: planning permission is needed. We handle the drawings, engineer and warrant as part of the job; see our building warrant guide.
How long does it take?
Drawings and warrant: 8–12 weeks before anything happens on site. Build: 10–14 weeks for a single-storey extension, 16–22 weeks for double-storey. Plan for the kitchen or bathroom fit-out at the end of that.
A recent example
New-build garage on the southside: foundations, blockwork, flat roof, rendered and painted, sectional door. Around five weeks on site with a two-man team, finished ready to use. The same method and team build our extensions — see the house extensions page for photos.
How we price an extension
Site visit and trial hole, then a written fixed price broken down line by line — groundworks, structure, roof, glazing, services, finishes — so you can see where every pound goes and take items out if the budget needs it. Payment in stages tied to progress, never large sums up front. 12-month workmanship guarantee and full public liability insurance.
Frequently asked questions
How much does a 20 m² extension cost in Glasgow?
Typically £45,000–£65,000 including VAT, drawings and building warrant for a standard finish. Add £7,000–£15,000 if a kitchen is being fitted inside it.
Do I need planning permission for a rear extension in Glasgow?
Usually not for a single-storey rear extension within permitted development limits (up to 4 m for detached, 3 m for semi-detached or terraced houses). You always need a building warrant. Flats and conservation areas need planning permission.
Is a flat roof or pitched roof cheaper?
A warm flat roof is cheaper to build and easier to add roof lanterns to. A pitched roof costs more but suits period houses and lasts longer without maintenance.
Can I live in the house during the build?
Yes — most clients do. The knock-through to the existing house is left until the new structure is watertight, so you lose the kitchen for two to three weeks at the end, not for the whole build.
Does an extension add value to a Glasgow home?
A well-built kitchen-diner extension in a southside or West End suburb typically adds more than it costs, especially on three-bed semis where family space is the limiting factor. Poorly finished extensions do not.
Do you do the kitchen and bathroom as well?
Yes. One team takes the job from foundations to finished kitchen, so there is no gap between builder and fitter.
Want a fixed price for your extension? Call 07568 582337 or request a site visit. Free quote within 48 hours of the visit. Home Decor Zone Ltd, 57 Ravenscraig Drive, Glasgow G53 6LQ.