House Extension Cost Birmingham 2026: Local Prices & Guide
West Midlands pricing for extensions and conversions — with area-by-area differences across Birmingham and Solihull
Buildcostr.ai · July 2026 · 6 min read
House extension costs in Birmingham 2026
Birmingham broadly tracks the UK national average for extension costs — making it more affordable than London and the South East, but broadly comparable to other large English cities. The West Midlands has a strong base of residential builders and good material supply chains, supporting competitive pricing across the region.
| Extension type | Birmingham cost range (2026) |
|---|---|
| Single-storey rear extension (20m²) | £32,000–£54,000 |
| Single-storey rear extension (30m²) | £48,000–£81,000 |
| Single-storey rear extension (40m²) | £64,000–£108,000 |
| Double-storey rear extension (20m² per floor) | £65,000–£105,000 |
| Wrap-around (rear + side return) | £72,000–£125,000 |
| Loft conversion — dormer | £33,000–£52,000 |
| Loft conversion — mansard | £50,000–£70,000 |
| Garage conversion | £10,000–£24,000 |
Materials and labour only. Add VAT at 20%, architect fees, structural engineer and building regulations for total project costs.
Price variation across the West Midlands
Solihull, Knowle, Dorridge and surrounding villages
The most expensive area in the West Midlands for residential extension work. Solihull's high property values attract premium contractors who regularly work on high-specification projects. Budget 15–25% above central Birmingham rates. A 30m² rear extension in Knowle can easily reach £90,000–£110,000 at mid-to-high spec.
Sutton Coldfield, Edgbaston, Harborne, Moseley
Birmingham's affluent inner suburbs. Good contractor demand and higher average specifications push prices 10–15% above the Birmingham average. These areas have a strong independent builder market with experienced residential tradespeople. Conservation area coverage in parts of Edgbaston and Harborne means planning advice is worth taking early.
Central Birmingham suburbs (Erdington, Kings Heath, Acocks Green, Hall Green)
Broadly in line with the regional averages in the table. Strong availability of local builders and competitive pricing. The large stock of 1930s semi-detached and terraced housing creates consistent demand for single-storey rear extensions.
Black Country and outer West Midlands (Wolverhampton, Walsall, Dudley, West Bromwich)
Generally 5–10% below the Birmingham averages, with good contractor availability. Pricing is competitive and the volume of residential extension work in these areas means most builders have solid experience with standard project types.
1930s semi-detached houses: the Birmingham staple
The most common extension project in Birmingham is a single-storey rear extension on a 1930s semi-detached house. These properties typically have: a generous rear garden, an existing side passage, a rear kitchen that can be extended and opened up, and cavity walls that may need insulation upgrading as part of the works.
The 1930s building stock is generally straightforward to extend — solid strip foundations, standard brick construction, and no party wall complications on the non-attached side. Most projects of this type do not require planning permission under permitted development, keeping pre-construction costs low.
Planning permission in Birmingham
National permitted development rules apply across Birmingham and the wider West Midlands. Birmingham City Council has designated conservation areas in Edgbaston, Harborne village, Bournville and a number of other historic areas where PD rights are restricted. Always verify your planning status before committing to architect and survey fees.
For the full guide to what requires planning permission and what doesn't, read do I need planning permission for a house extension.
Getting an accurate Birmingham extension cost
Birmingham's competitive contractor market means quote variation can be significant. Independent builders, regional firms and national contractors all operate in the West Midlands at very different price points. A professional cost plan from your architectural drawings benchmarks the market before you tender.
Buildcostr.ai applies West Midlands regional pricing data across all 15 NRM2 cost sections to produce your cost plan in 30 minutes. See a sample report or order yours from £99.
Also useful: UK house extension costs 2026 · kitchen extension costs · loft conversion costs
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