Kitchen Extension Costs UK 2025: Single Storey, Wrap-Around & More
Adding a kitchen extension remains the UK's most popular — and often most transformative — home improvement project. It creates open-plan living space, adds value, and solves the chronic issue of the cramped Victorian or 1930s kitchen that was never designed for modern family life. But it is also a significant investment with meaningful planning, structural, and neighbour implications. This guide covers the main extension types, what they cost in 2025, what the planning rules mean in practice, and how to get the project right.
Types of Kitchen Extension
Single-storey rear extension. The most common type: the kitchen is extended backwards into the rear garden. Usually built under Permitted Development (PD) rights without requiring formal planning permission, subject to size limits. Suits terraced, semi-detached, and detached houses.
Side return extension. Specific to Victorian and Edwardian terraced and semi-detached houses, which have a narrow passageway alongside the house (the "side return"). Infilling this space creates a wider, L-shaped kitchen without taking garden depth. Often combined with a rear extension for a wrap-around.
Wrap-around extension. Combines a single-storey rear and side return extension in one project. Maximises ground-floor space, but the complexity of the L-shape adds cost and is more likely to require planning permission depending on the total footprint.
Over-garage extension. A first-floor extension built over an integral or attached garage. More complex structurally, and almost always requires planning permission, but can add significant floor area without affecting the garden.
Extension Size vs Cost
| Extension Size | Estimated Cost (2025) |
|---|---|
| 3m × 4m (12m²) — rear only | £18,000–£30,000 |
| 4m × 4m (16m²) — rear only | £24,000–£40,000 |
| 5m × 5m (25m²) — larger rear | £37,500–£62,500 |
| Side return infill (typical) | £25,000–£45,000 |
| Wrap-around (rear + side return) | £40,000–£80,000+ |
Build costs are typically calculated at £1,500–£2,500/m² for a good-quality single-storey extension. Budget end (£1,500/m²) covers standard block construction, basic roof, and structural elements only. Premium end (£2,500/m²) includes higher-spec finishes, more complex rooflines, and glazing upgrades. London adds 20–30% to these figures.
What Adds Cost Beyond the Shell
The structural shell of an extension is only part of the budget. These items add significant cost and should be included in any initial estimate:
| Addition | Typical Cost |
|---|---|
| Bi-fold doors (per set) | £3,000–£8,000 |
| Sliding doors (per set) | £2,500–£6,000 |
| Lantern rooflight (per unit) | £2,000–£5,000 |
| Flat roof skylight (per unit) | £800–£2,000 |
| Underfloor heating (wet system) | £50–£100/m² |
| Structural steel (RSJ beam) | £800–£2,500 per beam |
| Kitchen fitting (mid-range) | £8,000–£20,000 |
| Architectural fees | 5–10% of build cost |
| Planning application (if required) | £258 (England, 2025) |
Permitted Development vs Planning Permission
The rules under England's Town and Country Planning (General Permitted Development) Order 2015 (as amended) are more generous than many homeowners realise — but the thresholds are precise.
Under Permitted Development (no application required):
- Detached house: rear extension up to 4m deep (single storey)
- Semi-detached or terraced: rear extension up to 3m deep (single storey)
- Maximum height: 4m for a pitched roof, 3m for any other roof type
- No extension can be closer to a highway than the original house
Neighbour Consultation Scheme (Larger Home Extension): Under a separate procedure, detached houses can extend up to 8m to the rear, and other houses up to 6m, without full planning permission — but neighbours must be formally notified and can object. If no valid objection is received, the local authority issues a Prior Approval notice.
When you will need planning permission:
- Total extension area exceeds 50% of the original garden area
- The side return extension is on a corner plot (more complex rules)
- Your property is listed or sits within a conservation area with Article 4 restrictions
- The over-garage extension is a first-floor addition
Always confirm PD eligibility with your local planning authority before starting. PD rights can be removed by condition on the original planning consent, which many homeowners are unaware of.
The Party Wall Act
If your extension is within 3m of a neighbouring property's foundations, or if the works involve excavation near a shared boundary, the Party Wall etc. Act 1996 is triggered. You must serve formal written notice on affected neighbours at least two months before construction begins (or one month for building on the boundary line itself).
If neighbours consent in writing, you can proceed. If they dissent, or fail to respond within 14 days, a Party Wall Award must be agreed through appointed surveyors — costs range from £700–£1,500 per surveyor (each party appoints their own, or both agree on one agreed surveyor). This cost is borne by the building owner, not the neighbour.
Typical Timeline
| Stage | Duration |
|---|---|
| Architect drawings and specification | 4–6 weeks |
| Planning application (if required) | 8 weeks statutory determination |
| Building Regulations submission | 2–4 weeks (full plans or building notice) |
| Party Wall notice period | 2 months minimum |
| Construction (single-storey extension) | 10–16 weeks |
| Kitchen fitting and decoration | 3–5 weeks |
Realistically, from appointing an architect to moving into your new kitchen is 6–9 months if planning permission is needed, or 4–6 months under PD.
Does a Kitchen Extension Add Value?
Research consistently shows that a well-executed single-storey kitchen extension adds between £20,000 and £50,000 to property values in most UK regions, depending on location, quality, and size. In London and the South East, the return can exceed the build cost. In slower markets, payback ratios are less certain — though the improvement in liveability is near-universal.
The key is quality: an extension that looks tacked-on, uses cheap materials, or creates awkward sightlines will not achieve the same uplift as a well-designed, well-integrated space.
Architect vs Design-and-Build
Architect-led route: You appoint an architect to design the project, produce drawings for planning and Building Regulations, and manage the build via a traditional contract with a main contractor. More control, potentially higher quality, typically better value at larger budgets.
Design-and-build firm: A single company handles design and construction. Faster and simpler procurement, particularly for standard extensions. Quality varies widely. Compare specifications carefully — not just price.
For extensions over £60,000 or involving complex planning, the architect route typically justifies its fee. Platforms like Renovate Me can help you map the full sequence of decisions — from planning feasibility to build finish — before you appoint anyone.
Next Steps
Confirm whether your project falls within Permitted Development or requires planning permission — your local planning authority's pre-application advice service (typically £50–£150) is money well spent. Appoint an architect for initial feasibility drawings before committing to a builder. Get at least three build quotes to comparable specifications. And start the Party Wall notice process early — delays here are the most common cause of project overrun.