Kitchen Extension Costs in Kent: Complete 2026 Price Guide

Kitchen extensions are the single most-requested project we deliver across Kent. The reason is straightforward — a properly designed kitchen-diner extension with bifold doors transforms how a family lives, adds £80,000–£200,000 to a property in West Kent, and costs less than moving. But the prices online are confusing. Here is what kitchen extensions actually cost in Kent in 2026, broken down by type, size and specification.

Kitchen Extension Costs at a Glance

Extension Type	Size	Total Cost	Per sqm
Side return (small)	6–10 sqm	£25,000–£40,000	£3,500–£4,500
Single-storey rear (mid)	18–25 sqm	£45,000–£75,000	£2,200–£3,200
Single-storey rear (premium)	25–40 sqm	£75,000–£140,000	£2,700–£4,000
Wrap-around	30–45 sqm	£85,000–£170,000	£2,500–£4,000
Two-storey with kitchen below	40–60 sqm	£100,000–£200,000+	£2,200–£3,500

These figures include the structural extension and the fitted kitchen as separate line items. Watch for quotes that exclude the kitchen — kitchen fittings on a quality extension typically run £15,000–£60,000 on top of the building work.

What is Different About a Kitchen Extension

A kitchen extension is not just an extension with a kitchen in it. The mechanical, electrical and plumbing requirements are significantly more complex than a living-room extension, and getting the design wrong produces an extension that is technically finished but practically unusable.

The differences:

• Mechanical extraction — proper extraction over a hob, ducted to outside, often through a flat roof
• Plumbing routing — sink, dishwasher, washing machine, sometimes a utility area, all draining to existing or new soil stacks
• Electrical loadings — ovens, hobs and fridges add significant load; consumer unit upgrades are common
• Underfloor heating — almost universal in extensions now, requires careful screed design and heat-source coordination
• Structural openings — knocking the existing kitchen wall through to the new extension creates the open-plan feel, but requires steelwork that is sometimes the most expensive single item in the build
• Glazing strategy — bifolds, sliding doors or roof lanterns each have different cost, thermal performance and aesthetic impacts

Kitchen Extension Types Explained

Side return (£25,000–£40,000)

The classic Victorian terrace kitchen extension. The narrow strip of side return is filled in with a glazed roof and matched-brick walls, widening the existing galley kitchen by 1.5–2.5m. Very common in central Tunbridge Wells, Sevenoaks and Tonbridge.

Best for: Victorian and Edwardian terraces.

Pros: Relatively cheap, often permitted development, transforms cramped galley kitchens into useable family rooms.

Cons: Limited to terraced and semi-detached homes with a side return; does not add a huge amount of floor area.

Single-storey rear (£45,000–£140,000)

The default kitchen-diner extension across Kent. A new room running the width or part-width of the rear elevation, typically 18–35 sqm. Almost always opens onto the garden via bifolds or sliders.

Best for: Most semi-detached and detached homes in Kent.

Pros: Maximum kitchen-diner usability, dramatic light from glazing, transforms the ground floor.

Cons: Reduces garden size, usually replaces all or most of the existing kitchen.

Wrap-around (£85,000–£170,000)

Combines a rear extension with a side return or side infill. The most common premium kitchen extension across Sevenoaks, Tunbridge Wells and the Weald — gives the largest possible open-plan kitchen-diner-living space.

Best for: Detached and end-of-terrace homes with both rear and side garden space.

Pros: Largest single kitchen extension type, transforms ground-floor layout.

Cons: Expensive, planning permission usually required, longest build.

Two-storey with kitchen below (£100,000–£200,000+)

A two-storey extension with the new kitchen-diner downstairs and a bedroom or bathroom upstairs. Common when families need a bedroom and a bigger kitchen at the same time.

Best for: Growing families needing both a bigger kitchen and an additional bedroom.

Pros: Two improvements for slightly less than two separate projects.

Cons: Most expensive option, longest build (16–22 weeks), planning permission almost always required.

What Drives the Cost

The kitchen itself

Kitchen fitting costs vary more wildly than any other element of an extension. Approximate ranges:

• Budget DIY-fit kitchens: £6,000–£12,000
• Mid-range fitted kitchens (Howdens, Wickes, John Lewis): £12,000–£25,000
• High-end fitted kitchens (DeVOL, Neptune, local cabinet makers): £25,000–£60,000
• Bespoke designer kitchens: £60,000–£150,000+

The same extension shell will cost £45,000 with a budget kitchen or £105,000 with a designer kitchen. Be specific about kitchen budget when comparing quotes.

Glazing

For a 25 sqm rear extension, glazing typically costs:

• 3-panel uPVC bifold + 2 windows: £4,000–£6,000
• 4-panel aluminium bifold + 2 windows: £8,000–£14,000
• Sliding door system (Schüco, Origin): £10,000–£18,000
• Roof lantern (3m × 1.5m): £3,000–£6,000

Premium aluminium glazing can easily be 25% of the entire extension cost. It is also the most visually impactful single decision.

Steelwork

Knocking through the existing kitchen wall to create open-plan space requires structural steel. A typical scenario:

• Single steel beam (4m span): £2,500–£4,000 supplied and fitted
• Double steel beam (longer span or load-bearing): £4,500–£8,000
• Goal-post frame (full-width opening): £6,000–£12,000

Always insist on a structural engineer's calculations — guesswork on steel sizes is dangerous.

Foundations

The Wealden clay common across Tonbridge, Hildenborough, Maidstone and the Weald often requires deeper-than-standard foundations. A 25 sqm rear extension typically needs:

• Standard strip foundations: £4,000–£6,000
• Trench-fill foundations (most common in clay): £6,000–£10,000
• Piled foundations (clay near mature trees): £10,000–£18,000

A site investigation early on (£600–£1,200) is the smartest money you can spend.

Underfloor heating

Wet underfloor heating in a 25 sqm extension typically costs £1,800–£3,500 supplied and fitted, plus screed and insulation costs of £1,500–£2,500. The thermal performance is materially better than radiators and the freed wall space is valuable in a kitchen.

Planning Permission for Kitchen Extensions in Kent

Most rear kitchen extensions are permitted development if they meet the following criteria:

• Single-storey, no taller than 4m (pitched) or 3m (flat)
• Maximum 6m beyond original rear wall (detached) / 4m (semi or terrace)
• No more than half of the original garden covered
• Materials similar to existing
• No side-facing first-floor windows without obscure glazing

Full planning permission is required for:

• Two-storey rear extensions in most cases
• Wrap-around extensions
• Properties in conservation areas (much of central Tunbridge Wells, parts of Sevenoaks and Tonbridge)
• Properties subject to Article 4 directions (Chislehurst)
• Properties in the Kent Downs AONB or High Weald AONB
• Listed buildings

Read our full guide to Kent planning permission for authority-by-authority detail.

What a £75,000 Kitchen Extension Looks Like in Kent

To make this concrete, here is what we typically deliver for £75,000 in 2026 (excluding the fitted kitchen):

• 25 sqm single-storey rear extension
• Trench-fill foundations to engineer's spec
• Brick and block cavity wall, matched to existing
• Insulated warm flat roof with single-ply membrane
• 4-panel aluminium bifold + 2 windows
• 3m × 1.5m roof lantern
• Wet underfloor heating, screed, insulation
• Replastered ceilings into existing kitchen, opened-up structural opening with steel
• All electrics, plumbing first-fix, ready for kitchen installation
• 24-month workmanship guarantee
• Building Control sign-off and completion certificate

Add £20,000–£40,000 for a quality fitted kitchen and you have a finished room for £95,000–£115,000.

Common Mistakes That Cost Money

Choosing kitchen and extension separately. The kitchen designer specifies a unit run that does not align with your structural openings. Coordinate from day one.

Skipping the structural engineer. Builders who quote "we'll work it out on site" are gambling with your house. A £600 engineer's report is non-negotiable.

Going cheap on glazing. uPVC bifolds dominate cheap quotes because they are 50% the cost of aluminium. They also flex, leak and look wrong on most period properties. The £4,000 you save costs your buyer £8,000 off the asking price.

Forgetting the boiler. The existing combi boiler probably cannot run a new kitchen, two new radiators and underfloor heating. Boiler upgrade £2,500–£4,500.

Underspecifying ventilation. A non-ducted recirculating extractor over a gas hob is fine for a small kitchen. In a 35 sqm open-plan kitchen-diner it is useless. Specify a ducted extractor running through the roof.

Building first, designing the kitchen second. Get the kitchen designer involved at the architect's drawing stage. Cabinet positioning affects window placement and structural opening width.

Kitchen Extension or Total Renovation?

If your existing kitchen layout is fundamentally bad, extending it sometimes makes the bad layout bigger rather than fixing it. We frequently advise clients in Tonbridge and Sevenoaks to consider:

• A smaller extension with a more thorough internal reconfiguration
• A full ground-floor renovation without extending
• Combining a side-return and rear extension to fundamentally rethink the floor plan

Sometimes a £45,000 extension and £25,000 internal works produces a better result than a £90,000 mega-extension.

Getting the Right Quote

A serious kitchen extension quote should include:

1. Site visit and measured survey
2. Structural engineer's report
3. Detailed itemised quote with provisional sums clearly marked
4. Planning permission status (or full application if needed)
5. Programme with critical milestones
6. Insurance and warranty details
7. Specifications for glazing, foundations, finish

We deliver kitchen extensions across Tonbridge, Tunbridge Wells, Sevenoaks, Maidstone, Ashford, Hildenborough, West Malling and Chislehurst.

Thinking about a kitchen extension? Call Carey Brothers on 07879 447975 or contact us for a free site visit and detailed written quote — no obligation.