📋 In This Guide
Planning a home extension in Birmingham or the West Midlands? Understanding costs upfront is essential for budgeting your project correctly. In 2026, Birmingham extension costs have risen slightly due to material and labour inflation, but the investment still delivers outstanding returns on property value.
At HSS Design & Build, we provide fully transparent, itemised quotes — no lump sums or hidden costs. This guide gives you real 2026 pricing data from projects across Birmingham and the West Midlands.
House Extension Cost Overview — Birmingham 2026
Building a home extension in Birmingham in 2026 costs between £1,800 and £2,500 per square metre for standard quality work, rising to £3,000+ per m² for high-specification or architecturally complex projects. These figures include labour and materials but exclude VAT (charged at 20% on most new extensions), planning fees, and architect costs.
Single-Storey
£35k–£55kTypical 20m² rear extension
Double-Storey
£60k–£90kTypical 30m² (2 floors)
Wrap-Around
£70k–£120kSide & rear combined
Kitchen Extension
£40k–£80kIncluding kitchen fit-out
Single-Storey Extension Costs in Birmingham 2026
A single-storey rear extension is the most popular type of home extension in Birmingham. It often falls under Permitted Development rights, and delivers significant living space improvements at a manageable cost.
| Extension Size | Standard Spec | Mid-Range Spec | High Spec |
|---|---|---|---|
| 10m² (small) | £18,000–£25,000 | £25,000–£33,000 | £33,000–£45,000 |
| 15m² (typical) | £27,000–£37,500 | £37,500–£50,000 | £50,000–£67,500 |
| 20m² (popular) | £36,000–£50,000 | £50,000–£65,000 | £65,000–£90,000 |
| 25m² (large) | £45,000–£62,500 | £62,500–£80,000 | £80,000–£110,000 |
Double-Storey Extension Costs in Birmingham 2026
A double-storey extension adds space on two levels simultaneously. The structural work is shared across both floors, making the cost per m² lower than a single-storey. Almost always requires planning permission.
| Combined Floor Area | Standard Spec | Mid-Range | High Spec |
|---|---|---|---|
| 20m² (10m² x 2) | £40,000–£55,000 | £55,000–£70,000 | £70,000–£95,000 |
| 30m² (15m² x 2) | £57,000–£78,000 | £78,000–£100,000 | £100,000–£135,000 |
| 40m² (20m² x 2) | £72,000–£100,000 | £100,000–£130,000 | £130,000–£175,000 |
Wrap-Around Extension Costs in Birmingham 2026
A wrap-around extension combines a rear extension with a side return extension, creating an L-shaped footprint. Particularly popular in Birmingham's Victorian and Edwardian terraced housing, where narrow side returns are often underused. Planning permission is typically required.
Costs range from £70,000 to £120,000+ depending on size and specification. The L-shaped structure, multiple roof junctions, and additional glazing make the per-m² cost slightly higher than a straightforward rear extension.
Kitchen Extension Costs in Birmingham 2026
A kitchen extension is one of the most popular reasons to extend in Birmingham — creating an open-plan kitchen-diner-living space. Costs:
- Extension structure only: £35,000–£65,000 (20–25m²)
- Budget kitchen fit-out: £5,000–£12,000
- Mid-range kitchen fit-out: £12,000–£25,000
- Luxury kitchen fit-out: £25,000–£60,000+
- Bi-fold or sliding doors: £3,000–£10,000
- Underfloor heating: £1,500–£4,000 additional
Total kitchen extension cost: £40,000–£80,000 for a 20m² extension with mid-range kitchen.
What Factors Affect Extension Costs in Birmingham?
1. Size and Footprint
The single biggest cost driver. Every additional square metre adds approximately £1,800–£2,500+ to the build cost. However, there are economies of scale — a 25m² extension typically costs less per m² than a 10m² extension.
2. Specification and Finish Quality
Key choices include: structural glazing (bi-folds vs. standard doors), roof specification (flat vs. lantern vs. pitched), floor finishes (tiles, engineered wood, polished concrete), and insulation specification. These choices can double the final cost.
3. Foundations and Ground Conditions
Birmingham's clay soil can require deeper or more complex foundations, adding £3,000–£10,000+ to costs. Properties near trees may require even deeper foundations due to root activity. HSS Design & Build conducts soil surveys as standard.
4. Party Wall and Neighbouring Properties
If your extension is adjacent to a shared boundary, the Party Wall Act 1996 applies. Surveyor fees typically range from £700–£2,000 per neighbour affected.
5. Structural Complexity
Knock-through works connecting the new extension to the existing property — removing walls, installing steel beams (RSJs) — typically add £3,000–£10,000 to the overall cost.
Full Cost Breakdown: 20m² Single-Storey Extension in Birmingham
| Cost Item | Typical Cost | Notes |
|---|---|---|
| Architect / Drawing Fees | £1,500–£3,000 | Planning + building regs drawings |
| Structural Engineer | £500–£1,200 | Calculations for steels and foundations |
| Planning Application Fee | £0–£258 | £0 if Permitted Development |
| Groundworks & Foundations | £5,000–£12,000 | Excavation, concrete, drainage |
| Brickwork / Structure | £8,000–£18,000 | Walls, steels, lintels |
| Roof | £4,000–£10,000 | Higher for pitched or lantern roof |
| Windows & Doors | £3,000–£12,000 | Higher for bi-folds or structural glazing |
| Plumbing & Electrics | £3,000–£7,000 | First fix + second fix |
| Plastering & Internal Finishing | £2,000–£5,000 | Skimming, coving, skirting |
| Flooring | £1,500–£6,000 | Tiles, engineered wood, or polished concrete |
| Knock-Through Works | £2,000–£8,000 | RSJ beam, making good |
| Decoration | £1,000–£3,000 | Painting and decorating |
| TOTAL (excl. VAT) | £31,500–£85,000 | Typically £36,000–£55,000 for standard-mid spec |
| VAT @ 20% | +£6,300–£11,000 | VAT applies to most new extensions |
Does a House Extension Add Value in Birmingham?
In most cases, yes — significantly. A well-built extension in Birmingham typically adds 10–25% to your property's value:
- A kitchen-diner extension creating open-plan living adds on average 8–15% to value
- Adding a 4th bedroom via an extension adds 10–20% to value
- A master bedroom with en-suite adds approximately 5–10% to value
- Wrap-around extensions on Victorian terraces in prime Birmingham postcodes can add 20–30%
The key to maximising added value is quality of finish, natural light, connection between new and old space, and appropriate specification for your area. HSS Design & Build designs extensions with both your lifestyle and resale value in mind.
Get a Free, Itemised Extension Quote in Birmingham
HSS Design & Build provides transparent, fully itemised quotes for home extensions across Birmingham and the West Midlands. No hidden costs, no lump sums — honest pricing from accredited local professionals.
Get Your Free Quote TodayCall: 0203 909 0313 | 110 Hagley Road West, Birmingham B67 5EZ
Or explore our flexible finance options to spread the cost
Frequently Asked Questions: House Extension Costs Birmingham 2026
How much does a single-storey extension cost in Birmingham in 2026?
A single-storey rear extension in Birmingham costs approximately £1,800 to £2,500 per square metre in 2026. A typical 20m² extension costs £36,000 to £55,000 including labour and materials but excluding VAT at 20% and architect fees.
How much does a double-storey extension cost in Birmingham?
A double-storey extension in Birmingham costs approximately £1,500 to £2,200 per square metre combined floor area. A typical 30m² double-storey extension costs £60,000 to £90,000 in the West Midlands in 2026. Double-storey extensions offer better value per m² than single-storey due to shared structural costs.
What is the cheapest type of house extension in Birmingham?
The most cost-effective home extension in Birmingham is a small single-storey rear extension under Permitted Development rights. A basic 10–15m² extension can be achieved for £18,000–£37,500 at standard specification, saving money by avoiding planning fees and delays.
How long does a house extension take to build in Birmingham?
A single-storey extension in Birmingham takes 8 to 14 weeks to build from groundworks to completion. A double-storey extension takes 12 to 20 weeks. The full process from initial enquiry to handover — including design, planning, and construction — typically takes 4 to 8 months.