Average Cost of a Bungalow Extension in 2026 (UK)
A bungalow extension costs roughly £2,000–£2,800 per m² in 2026 for a good-quality single-storey build. That puts a typical 20m² rear extension at around £40,000–£56,000, rising to £80,000–£110,000+ for a large wrap-around with premium glazing and a new kitchen. Bungalows are often quicker and a little cheaper to extend than two-storey homes — single-storey work needs less scaffolding and access is usually easier — but reconfiguring the roof and staying inside permitted development can move the figure. Here's the full 2026 breakdown.
Bungalow extension costs at a glance — 2026
Standard specification, finished. Source: BestBuilders 2026 quote data across 519 UK towns. Figures exclude VAT variances and unusually difficult access or ground conditions.
Bungalow extension cost by size (2026)
Most bungalow extensions are single-storey rear or side additions, so cost tracks floor area closely. The table below assumes a standard warm-roof build, mid-range glazing and a plastered, decorated interior ready for furniture. A kitchen or bathroom fit-out, big glazing or a knock-through into the existing rooms pushes you toward the upper column.
| Size | Typical cost (standard) | With premium glazing & fit-out |
|---|---|---|
| 15m² (small rear) | £30,000–£42,000 | £44,000–£52,000 |
| 20m² (typical rear) | £40,000–£56,000 | £58,000–£68,000 |
| 25m² (mid-size) | £50,000–£68,000 | £70,000–£82,000 |
| 30m² (large) | £60,000–£84,000 | £86,000–£98,000 |
| 40m² (wrap-around) | £80,000–£110,000 | £112,000–£135,000 |
Ranges assume standard foundations and a mid-range specification. London and the South-East typically sit 15–25% above these figures.
Where the money goes
Understanding how the budget splits helps you see where a quote is padded and where it is realistic. On a typical bungalow extension the shares look like this:
| Element | Share of budget | Notes |
|---|---|---|
| Foundations & groundworks | 15–20% | Rises sharply with poor ground, trees or drainage runs under the footprint |
| Structure (walls, roof, any steel) | 30–35% | Single-storey walls plus a warm flat or pitched roof, and a beam for any knock-through |
| Glazing (doors, rooflight/lantern) | 15–25% | Biggest single variable — bi-folds and lanterns add fast |
| Internal fit-out | 20–30% | A kitchen or bathroom fit-out pushes the top of the range |
| Fees & regs | 5–10% | Design, structural engineer, Building Control and any party-wall work |
Types of bungalow extension and what they cost
Bungalows suit several extension routes because everything happens at ground level. The right choice depends on your plot, your budget and whether you want more floor area or more head height.
| Type | Best for | Typical cost |
|---|---|---|
| Rear extension | Bigger kitchen or living space onto the garden | £40,000–£70,000 |
| Side extension | Using a wide plot for an extra room or utility | £35,000–£60,000 |
| Wrap-around (rear + side) | A large open-plan kitchen-diner | £80,000–£135,000 |
| Loft / dormer conversion | Adding a bedroom without losing garden | £45,000–£75,000 |
| Porch or small front addition | Entrance, storage and kerb appeal | £6,000–£15,000 |
A loft conversion is often overlooked on a bungalow, yet the generous roof void many bungalows have can make it one of the most cost-effective ways to add a bedroom. If you need ground-floor living space, a rear or wrap-around extension is the usual answer.
Cost by region
Where you live is one of the biggest drivers of the final bill, because it sets labour rates. The same 20m² bungalow rear extension can vary by £15,000 or more between the cheapest and most expensive regions.
| Region | Typical 20m² rear extension | vs UK average |
|---|---|---|
| London | £52,000–£70,000 | +20–25% |
| South East | £46,000–£62,000 | +10–15% |
| South West & East | £42,000–£56,000 | Around average |
| Midlands | £40,000–£53,000 | −5% |
| North & Scotland | £36,000–£50,000 | −10–15% |
| Wales & Northern Ireland | £35,000–£48,000 | −10–15% |
Regional figures are a guide only — access, ground conditions and specification still move each project. Always compare three quotes on the same drawings.
What is in the price — and what isn't
A builder's quote usually covers the shell and the standard finish. Several genuine costs sit outside a typical fixed price, so budget for them separately rather than being surprised part way through.
Usually included
- Foundations, walls, roof structure and covering
- Standard windows and one set of doors
- First-fix and second-fix electrics and plumbing to a standard layout
- Plastering, flooring screed, and basic decoration
- Building Control inspection fees where stated
Usually extra
- Removing the existing structure — taking down a conservatory, garage wall or old lean-to, plus a skip for the waste, typically £800–£3,000.
- Kitchen or bathroom fit-out — units, worktops, tiling and appliances add £8,000–£25,000.
- Premium glazing — bi-fold or sliding doors and a roof lantern add £4,000–£9,000.
- Drainage diversions — a manhole or drain run under the footprint costs £800–£2,500 to move.
- Design and structural fees — drawings and calculations of £1,500–£4,000.
- Contingency — hold back 10–15% for what the ground reveals.
How long a bungalow extension takes
A single-storey bungalow extension is usually quicker than a two-storey build. Expect roughly 10–16 weeks on site for a standard rear extension, and up to 20 weeks for a large wrap-around or where the roof needs reworking.
- Weeks −4 to 0 — survey, drawings, structural calculations, planning check and Building Regs submission.
- Weeks 1–2 — groundworks: footings dug and poured, drains dealt with, slab laid.
- Weeks 3–6 — walls up, any steel in, roof structure and covering, made watertight.
- Weeks 7–9 — glazing in, first-fix services, insulation and plasterboard.
- Weeks 10–16 — plastering, floors, second fix, decoration, snagging and Building Control sign-off.
How long it lasts
A well-built bungalow extension is a permanent part of the house and will last as long as the original building with normal maintenance. The parts that wear first are the finishes and the roof covering: a modern warm flat roof in EPDM, GRP or single-ply typically carries a 20–25 year guarantee, while a tiled pitched roof can last 40–60 years. Kitchens and bathrooms are usually refreshed every 10–20 years regardless of the structure around them. Insisting on a warm-roof build-up and proper falls at the quote stage is the single best way to avoid problems later.
Planning permission and building regulations
Many single-storey bungalow rear extensions fall under permitted development, which means no full planning application — but the limits matter and they are easy to trip over. For a detached house a single-storey rear extension can extend up to 4m under permitted development (8m under the larger home extension scheme with prior approval), with height limits that a bungalow can bump into because the eaves are low. A wrap-around combining rear and side almost always needs full planning permission.
Whatever route you take, get a Lawful Development Certificate to prove the work was legal when you come to sell. See our guide on whether you need planning permission for an extension.
Building regulations always apply, even under permitted development. They cover structure, insulation, fire safety, drainage and ventilation, and the work is signed off by Building Control or an approved inspector. Your builder should include the inspection fees and hand you the completion certificate at the end — you will need it when you sell.
Checklist for hiring a contractor
Use these checks yourself before you sign anything — they are the questions a careful homeowner asks:
- Ask to see two recent single-storey extensions you can visit or phone about — not just general building work.
- Check their public liability insurance yourself and confirm it is current — ask for the certificate and the insurer.
- Make sure the quote names the roof spec (covering type, a warm-roof build-up and adequate falls) rather than leaving it vague.
- Agree a written stage-payment schedule — never pay more than 10–15% up front.
- Get three itemised quotes on identical drawings so the numbers are genuinely comparable.
- Confirm who arranges Building Control and who provides the completion certificate.
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