Kitchen Extension Cost UK 2026: Build + Fit-Out Price Guide

A kitchen extension in the UK costs between £35,000 and £95,000 on average in 2026. The construction shell costs £1,800 to £2,600 per m² (excluding VAT), while the new kitchen units, worktops, and appliances add £8,000 to £25,000+ depending on specification, layout, and structural steelwork.

A kitchen extension is consistently the most popular and value-adding home improvement project in the UK, transforming dated, cramped back rooms into light-filled open-plan kitchen-diners. However, unlike standard residential extensions where the builder's quote covers nearly everything, a kitchen extension involves two distinct budgets that must be managed in parallel: the structural building shell (groundwork, walls, roof, insulation, and glazing) and the internal kitchen fit-out (cabinetry, stone worktops, appliances, plumbing feeds, and electrical circuits).

How Much Does a Kitchen Extension Cost in the UK?

A standard kitchen extension in the UK costs between £1,800 and £2,600 per m² for the builder's shell, with total turnkey costs ranging from £35,000 to over £120,000 once the kitchen fit-out, professional fees, and 20% VAT are included. The final figure is driven by three variables: the square metreage of new floor area, the complexity of structural load-bearing wall removals, and the specification tier of your chosen kitchen cabinetry and work surfaces.

Total Kitchen Extension Budget = [Builder Shell (£1,800-£2,600/m²)] 
                               + [Structural Steel / Knock-Through (£2,000-£5,000)]
                               + [Kitchen Units & Appliances (£8,000-£25,000+)]
                               + [Glazing & Rooflights (£3,000-£9,000)]
                               + [Professional Fees & Approvals (£3,000-£6,000)]
                               + [20% VAT + 12% Contingency]

Average Cost per Square Metre (£/m²): Shell vs Fully Fitted

When consulting building contractors and architects, quotes are usually split into two fundamental rates: the structural "shell-only" rate and the "turnkey completed" rate.

Shell Build Cost vs Kitchen Fit-Out: Understanding the Two Budgets

One of the most dangerous budgeting mistakes UK homeowners make is treating a builder's estimate as an all-inclusive cost. In reality, a kitchen extension requires managing two distinct financial pots:

• The Structural Shell Budget (60% to 70% of outlay): Pays the main building contractor to construct the physical building envelope. It covers site clearance, foundation trenching, damp-proof membranes, exterior cavity walls, structural steel RSJ installations for knock-throughs, roof carpentry, roofing membranes/tiles, external glazing (bifold doors and rooflights), first-fix plumbing pipework, first-fix electrical cabling, insulation, plasterboarding, and multi-finish plaster skimming.
• The Kitchen Fit-Out Budget (30% to 40% of outlay): Covers the internal elements that transform an empty plastered room into a functioning culinary living space. This includes kitchen cabinetry units, kitchen island structures, worktops, splashbacks, sink and tap fixtures, built-in and freestanding appliances (oven, hob, extractor, dishwasher, American fridge-freezer), second-fix plumbing and electrical hook-ups, flooring (porcelain tiles, engineered oak, or microcement), and decorative painting.

Worked Cost Examples by Kitchen Extension Size (15m², 20m², 30m²)

Because kitchen extension costs vary significantly depending on total floor area and the ratio of building work to cabinetry installation, reviewing realistic, worked financial breakdowns is the most reliable way to assess your project's viability.

15m² Kitchen Extension (Side Return or Small Rear Infill) — £35,000 to £55,000

A 15m² kitchen extension typically costs between £35,000 and £55,000 all-in, representing the standard size for a Victorian or Edwardian terraced house side-return infill (approx. 2m x 7.5m) or a compact suburban rear extension (approx. 3m x 5m). This footprint is ideal for expanding a narrow, dark galley kitchen into an airy space with room for a dining table and garden access.

20m² Kitchen Extension (Standard Family Kitchen-Diner) — £50,000 to £85,000

A 20m² kitchen extension costs between £50,000 and £85,000 all-in, representing the most common domestic extension footprint in the UK (such as a 4m x 5m or 3.5m x 5.7m rear extension on a semi-detached property). This size creates a generous open-plan kitchen-diner with enough floor space to incorporate a central 2-metre kitchen island, breakfast bar seating, dedicated dining area, and wall-to-wall glazing opening onto the garden.

30m² Kitchen Extension (Large Open-Plan Living-Kitchen with Island) — £80,000 to £140,000+

A 30m² kitchen extension costs between £80,000 and £140,000+ all-in, typically configured as a 6m x 5m rear extension or a substantial wrap-around extension across the rear and side of a detached or semi-detached home. A 30m² footprint creates a complete "super-room" that replaces the need for separate downstairs rooms, combining a luxury fitted kitchen, a large 3-metre island, a full 8-seater dining area, and a soft lounge seating zone overlooking the garden.

Kitchen Extension Costs by Layout Type

The architectural layout of your home dictates whether your kitchen extension extends directly into the rear garden, fills in an underused side pathway, or wraps around two elevations. Each layout comes with distinct structural complexities and pricing profiles:

[Rear Extension]              [Side Return]                  [Wrap-Around]
+-----------+                 +-----+-----+                  +-----+-----+
|  Kitchen  |                 | Bed | Bed |                  | Bed | Bed |
+-----------+                 +-----+-----+                  +-----+-----+
| NEW REAR  |                 | Kit | NEW |                  | NEW | NEW |
| EXTENSION |                 |     | IN- |                  | SIDE| REAR|
+-----------+                 +-----+FILL +                  +-----+-----+

Single-Storey Rear Kitchen Extension

A single-storey rear extension extends directly outward from the original back wall into the rear garden.

• Average Cost: £1,800 to £2,500 per m² (Shell) | £40,000 to £90,000 (Turnkey).
• Key Characteristics: This is the most straightforward extension style to build. It typically spans the full or partial width of the house, extending 3 to 4 metres into the garden.
• Cost Advantage: It usually qualifies under Class A Permitted Development, avoiding full planning delays.
• Structural Consideration: Requires opening the rear load-bearing wall with a single or paired RSJ steel beam.

Victorian/Edwardian Side Return Extension

A side return extension infills the narrow, unused alleyway running alongside the rear projection ("outrigger") of typical Victorian and Edwardian terraced houses.

• Average Cost: £2,000 to £2,800 per m² (Shell) | £42,000 to £75,000 (Turnkey).
• Key Characteristics: Although it only adds 8m² to 15m² of new footprint, it transforms the entire ground floor by converting a dark 2.5m wide galley kitchen into a light, 4.5m to 5.5m wide open-plan room.
• Structural Consideration: Because the extension is built right along the shared boundary, it almost always requires a formal Party Wall Agreement with your neighbour. Additionally, because the existing outrigger wall must be completely removed, heavy longitudinal structural steelwork is required to support the first-floor bedroom masonry above.

Wrap-Around (L-Shaped) Kitchen Extension

A wrap-around extension combines a side return extension and a rear extension into a single continuous L-shaped build.

• Average Cost: £2,200 to £3,200 per m² (Shell) | £75,000 to £145,000+ (Turnkey).
• Key Characteristics: Wrap-around extensions deliver the largest footprint increase, often generating 30m² to 50m² of transformative new living space.
• Structural Consideration: This is the most complex single-storey build possible. It requires removing two entire load-bearing exterior walls at right angles, necessitating a complex structural steel "goalpost" portal frame with central corner columns and engineered padstones. It almost never qualifies under Permitted Development and requires full planning permission.

Kitchen Fit-Out Costs by Specification Tier

The kitchen units, worktops, and appliances you choose represent the single most flexible variable in your overall budget. While building shell costs are largely fixed by local trade labour and material prices, kitchen fit-outs can range from £6,000 to well over £50,000.

Budget Fit-Out (£6,000 – £12,000): Laminate & Entry Appliances

A budget kitchen fit-out provides a clean, modern aesthetic using mass-manufactured cabinetry and entry-level branded appliances:

• Cabinetry: Flat-pack or standard pre-assembled 16mm or 18mm MFC carcases from trade suppliers such as Howdens (Lamona range), IKEA, or B&Q. Slab or simple shaker laminate doors.
• Worktops: 38mm post-formed high-pressure laminate with matching upstands (£20–£40 per linear metre).
• Appliances: Entry-level integrated appliances from Beko, Indesit, or Hisense (electric fan oven, 4-zone ceramic/induction hob, integrated 60cm dishwasher, extractor hood).
• Sink & Taps: Stainless steel single or 1.5 bowl inset sink with chrome monobloc mixer tap.
• Installation: Standard kitchen fitter labour: £1,500 to £2,500 (5 to 7 days work).

Mid-Range Fit-Out (£12,000 – £25,000): Quartz, Integrated Bosch/Neff, Underfloor Heating

The mid-range tier represents the sweet spot for UK family homes, combining durability, premium aesthetics, and long-term resale appeal:

• Cabinetry: Sturdy 18mm colour-matched carcases with soft-close Blum hinges and drawers from suppliers such as Magnet, Wren (Infinity Plus), or Wickes. Painted timber effect or handleless true-J-pull profile doors.
• Worktops: Templated and factory-fabricated 20mm or 30mm engineered quartz (such as Silestone or Compac) with recessed draining grooves and polished undermount cut-out (£200–£400 per linear metre).
• Appliances: Mid-to-high specification integrated appliances from Bosch, Neff, or Siemens (pyrolytic self-cleaning oven, Slide&Hide door, 70cm flex-induction hob, 9kg integrated washing machine).
• Sink & Taps: Composite granite (Silgranit) or brushed steel undermount sink with pull-out spray tap or entry-level instant boiling water tap.
• Installation: Professional installation, electrical second-fix, and plumbing hook-up: £2,500 to £4,500.

Premium / Luxury Fit-Out (£30,000 – £60,000+): Bespoke Cabinetry, Dekton, Bora Downdraft

For high-value properties or architectural showpieces, a luxury kitchen fit-out incorporates bespoke craftsmanship and commercial-grade culinary technology:

• Cabinetry: Custom handmade solid hardwood in-frame shaker or book-matched architectural veneer cabinetry crafted by bespoke joinery companies (such as Tom Howley, Harvey Jones, or bespoke local cabinetmakers) with solid oak dovetail drawers and custom pantry larders.
• Worktops: Ultra-compact sintered stone surfaces such as Dekton or Neolith, or natural Calacatta marble/granite, featuring mitred 50mm waterfall edges cascading down the island sides (£450–£750+ per linear metre).
• Appliances: Premium German and American appliances from Miele, Gaggenau, Sub-Zero, or Bora (Bora Pure venting induction hob, dual steam-combination ovens, integrated wine climatisation cabinets, full-height larder fridge and freezer columns).
• Sink & Taps: Quooker Flex or Fusion instant 100°C boiling, chilled, and sparkling water tap system (£1,400–£2,500 fitted).
• Installation: Specialist master joinery installation: £5,000 to £10,000+.

Kitchen Extension Cost by UK Region: 2026 Price Matrix

Contractor labour rates, scaffolding fees, plant hire, and skip disposal vary significantly across the UK. Building a 20m² kitchen extension in Central London can cost 35% to 45% more than building the identical project in Yorkshire or Wales.

The table below illustrates the regional cost adjustments across mainland UK for a standard 20m² kitchen extension (inclusive of standard shell build, mid-range kitchen fit-out, and 20% VAT):

What Drives the Cost of a Kitchen Extension? (The Technical Factors)

Beyond the size of the room and the kitchen brand, five critical technical and structural factors frequently cause kitchen extension quotes to escalate:

Knock-Throughs and Structural Steelwork (RSJ Beams & Portal Frames)

To merge your existing house into the new extension and create an unbroken open-plan space, the existing external load-bearing wall must be removed. Because that exterior wall supports the upper floor joists, second-storey brickwork, and roof, it must be temporarily propped with steel Acrow props and Strongboy attachments while builders install heavy structural steel beams:

• Single Opening (up to 3.5m span): A single or paired rolled steel joist (RSJ) resting on engineered concrete padstones costs £1,800 to £3,200 including supply, structural engineer calculations, craning, and padstone installation.
• Full-Width Knock-Through / Goalpost Portal (4m to 6m span): When knocking out the entire back wall and side wall (in a wrap-around build), a simple beam is structurally insufficient to resist wind overturning loads. Contractors must install a welded steel "goalpost" portal frame consisting of two vertical universal columns (UCs) bolted to heavy floor pad foundations and an overhead universal beam. A steel goalpost frame costs £4,000 to £8,500 supplied, crane-lifted into position, and fire-boarded.

Drainage, Soil Pipes, and Water Board Build-Over Agreements

Moving a kitchen almost always requires relocating underground foul drainage:

• Sewer & Manhole Relocation: Kitchen extensions frequently cover existing inspection chambers (manholes) or gullies located in the garden patio. Building regulations prohibit keeping an unsealed manhole inside a habitable living room or kitchen. Moving the inspection chamber outside the new extension perimeter and diverting subterranean clay pipes costs £1,500 to £3,500.
• Statutory Build-Over Agreement: If your extension is built over or within 3.0 metres of a public sewer (a sewer pipe serving more than one property, which transferred to water authority ownership in 2011), you legally require a formal Build-Over Agreement from your regional water authority (such as Thames Water, Severn Trent, or United Utilities). Securing approval requires a pre- and post-construction CCTV drainage survey (£300–£600) and application fees (£350–£1,300).

Electrical Second-Fix, Dedicated Circuits, and Consumer Unit Upgrades

Modern open-plan kitchens place heavy electrical demands on a property's wiring infrastructure:

• Dedicated 32A Appliance Feeds: High-power appliances—such as induction hobs (7.2kW+), pyrolytic ovens, and instant boiling water taps—require their own dedicated radial circuits run back to the main consumer unit.
• Consumer Unit Upgrade: If your existing consumer unit (fuse board) is dated or lacks spare RCD-protected ways, Building Regulations Part P requires an upgrade to a modern metal 18th Edition dual-RCD or RCBO consumer unit, costing £650 to £1,200.
• Kitchen Lighting Circuits: Creating layered lighting (ceiling downlights, feature island pendants, under-cabinet LED strips, and garden plinth lights) typically costs £1,500 to £3,000 for first and second-fix electrical labour and materials.

Architectural Glazing: Bifold Doors, Sliding Doors, and Roof Lanterns

Maximising daylight is the primary aesthetic goal of modern kitchen extensions, but large expanses of structural glass carry high price tags:

• Aluminium Bifold Doors: 3-metre to 4-metre powder-coated aluminium bifold door sets cost £3,500 to £6,500 supplied and installed.
• Ultra-Slim Sliding Patio Doors: Large sliding doors with 20mm sightlines provide unobstructed garden views with fewer vertical frames than bifolds, costing £5,000 to £10,000+ installed.
• Roof Lanterns & Frameless Rooflights: A thermally broken aluminium roof lantern (e.g., 1.5m x 2.5m) costs £1,800 to £3,500 installed into a flat roof deck, while walk-on or flush frameless glass rooflights cost £1,200 to £2,500 each.

Underfloor Heating (Wet vs Electric) vs Radiator Relocation

Standard radiator panels consume valuable wall space that could otherwise be used for kitchen units, breakfast bars, or tall larder storage. Consequently, most kitchen extensions incorporate underfloor heating:

• Wet (Hydronic) Underfloor Heating (£1,500 – £3,000): Continuous plastic heating pipes embedded directly into the liquid floor screed and plumbed into your central boiler or heat pump via a dedicated manifold. Highly energy-efficient, produces gentle radiant heat across large tiled surfaces, and keeps walls completely free for cabinetry.
• Electric Mat Underfloor Heating (£600 – £1,400): Thin electric wire mesh laid directly beneath floor tiles. Cheaper to install initially, but substantially more expensive to run over time; best suited only for compact galley extensions under 10m².

Planning Permission and Building Regulations for Kitchen Extensions

Most single-storey kitchen extensions do not require full planning permission, but all kitchen extensions legally require council Building Regulations sign-off.

Permitted Development Limits (Depth, Eaves, Boundary Proximity)

Under Class A of the Town and Country Planning (General Permitted Development) Order, a single-storey rear kitchen extension can be built under Permitted Development rights without a planning application, provided it adheres to all statutory limits:

• Rear Depth (Standard): Must not extend beyond the original rear wall by more than 3.0 metres for attached houses (terraced/semi-detached) or 4.0 metres for detached houses.
• Larger Home Extension Scheme (Prior Approval): Under the Neighbour Consultation Scheme, you can extend up to 6.0 metres (attached) or 8.0 metres (detached), provided you submit a Prior Approval notification to the council and immediate neighbours raise no valid objections.
• Eaves & Ridge Height: Maximum height of 4.0 metres for a pitched roof. If the extension is built within 2.0 metres of a boundary, maximum eaves height cannot exceed 3.0 metres.
• Land Coverage: The extension (along with existing outbuildings) must not cover more than 50% of the total curtilage of the garden surrounding the original house.
• Materials: Exterior materials must be of similar appearance to the existing house.

The Building Regulations Part L Glazing Rule (The 25% Glazing Cap & SAP Calculations)

A critical Building Regulations hurdle that catches many homeowners unaware is the Part L 25% Glazing Limitation:

Glazing Allowance Formula:
Permitted Glazing Area = [25% of New Extension Floor Area] + [Area of Old Windows/Doors Replaced]

Under Approved Document L (Conservation of fuel and power), the total area of external windows, rooflights, and glazed doors must not exceed 25% of the floor area of the new extension (plus the area of any existing house openings covered by the extension).

Because modern open-plan kitchen extensions frequently feature 4-metre bifold doors and a large roof lantern, their glazing area routinely exceeds 40% to 60% of the floor area. To pass Building Control, your architect or energy assessor must submit a SAP Calculation (Standard Assessment Procedure). The SAP calculation proves that the extra heat loss through the excessive glass is compensated for by upgrading wall insulation, roof insulation, or boiler efficiency elsewhere in the building. An overglazed SAP assessment costs £150 to £350.

Part P (Electrical) and Part F (Kitchen Extraction Ventilation)

• Part P (Electrical Safety): Kitchens are categorised as "special locations" for electrical installations due to the proximity of water and electricity. All wiring work must be carried out and certified by a competent registered electrician (NICEIC or NAPIT), with a formal Part P Building Regulations Compliance Certificate issued upon completion.
• Part F (Ventilation): Kitchen extractors must meet minimum extraction flow rates: 30 litres per second (l/s) for cooker hoods ducted directly to the outside, or 60 l/s for wall/ceiling extractors positioned away from the hob. Recirculating filter hoods that do not vent externally may require an additional continuous mechanical background extractor.

How to Budget and Manage Your Kitchen Extension Project

Delivering a kitchen extension on budget requires disciplined project management, formal contractual milestones, and protective financial buffers.

Milestone Payment Schedule: How to Pay Your Builder Safely

Homeowners should never pay large upfront sums before work begins. Main building contracts (such as a standard JCT Home Owner contract) should link staged payments to tangible, completed construction phases verified by Building Control inspections:

1. Mobilisation Deposit (5%): Paid only when skips, plant, welfare facilities, and initial materials arrive on site.
2. Substructure & Slab (15%): Paid once foundations are poured, underground drainage laid, and concrete slab cast.
3. Superstructure & Wallplate (20%): Paid once exterior cavity walls are built up to roof level.
4. Wind & Water-Tight Shell (20%): Paid when roof tiling/membranes, roof lanterns, and bifold doors are installed and the building is weatherproof.
5. First-Fix & Plaster (20%): Paid once structural steels are signed off, electrical/plumbing first-fix is complete, and walls are skimmed.
6. Kitchen Installation & Second-Fix (15%): Paid when kitchen cabinetry, worktops, flooring, and appliances are connected and operational.
7. Practical Completion & Retention (5%): Retained until all snagging defects are remedied and the local council issues your official Building Regulations Completion Certificate.

Essential Professional Fees, VAT (20%), and the 12% Contingency Fund

When budgeting for a typical 20m² kitchen extension costing £55,000 to £80,000, ensure you allocate adequate funding across all professional and statutory categories:

• Architect / Technologist Planning Drawings: £1,200 – £2,800
• Structural Engineer Calculations (RSJ & Foundations): £600 – £1,400
• Building Control Inspection & Certificate Fees: £550 – £950
• Party Wall Surveyor Fees (if neighbours dissent): £900 – £2,200
• Thames Water / Water Board Build-Over Application: £350 – £1,200
• Overglazed SAP Energy Calculation: £150 – £350
• HM Revenue & Customs VAT (20% on all materials and contractor labour): £9,000 – £14,000
• Unallocated 12% Contingency Fund (for ground condition surprises): £6,000 – £9,500

Frequently Asked Questions

A quick note on estimates

Indicative 2026 UK figures derived from published RICS BCIS data, supplier price lists, and contractor benchmarks. The final cost of any building project depends heavily on your architectural drawings, ground stability, and chosen kitchen fittings. Always obtain at least three itemised, like-for-like quotes from vetted contractors. See our full disclaimer.

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