The open-plan kitchen-diner-living space is the single most sought-after feature in UK homes. Extending the rear of a house to create a bright, open ground-floor layout that connects the kitchen to the garden has transformed millions of homes over the past two decades — and remains the most popular reason homeowners commission an extension.

This guide covers everything involved in planning an open-plan kitchen extension: costs, planning permission, structural requirements, design considerations, and how to make the most of the available space.

What Does an Open-Plan Kitchen Extension Involve?

A typical open-plan kitchen extension project combines three elements:

• Rear extension: Adding depth to the ground floor to create more space for kitchen, dining, and living areas
• Internal wall removal: Removing one or more load-bearing internal walls to open up the existing ground floor and connect it to the extension
• Rear glazing: Installing bifold doors, sliding doors, or large fixed-glazing panels to open the back of the house to the garden

The result is a continuous living space flowing from front to back of the house, maximising natural light and indoor-outdoor connection.

Cost of an Open-Plan Kitchen Extension in 2025

Project Scope	Typical Cost Range (2025)
Small rear extension + wall removal + basic kitchen (Midlands/North)	£45,000–£70,000
Medium rear extension + wall removal + mid-range kitchen	£70,000–£110,000
Wrap-around extension + wall removal + full kitchen (Midlands/North)	£90,000–£140,000
Medium rear extension + wall removal + mid-range kitchen (London)	£100,000–£160,000
Wrap-around extension + premium kitchen fit-out (London)	£150,000–£250,000+

These ranges include architectural fees, structural engineering, planning, building regulations, construction, bifold doors, and kitchen supply and installation. VAT at 20% applies to new build work; some renovation elements may be eligible for reduced VAT.

The Kitchen Budget

Kitchen costs vary enormously and are often the single largest variable in the budget. Indicative ranges:

• Budget kitchen (Howdens, IKEA): £5,000–£12,000 supply and fit
• Mid-range kitchen (John Lewis, Wren, Magnet premium): £12,000–£25,000
• High-end kitchen (bespoke or premium brands): £25,000–£60,000+

Planning Permission for an Open-Plan Kitchen Extension

The planning permission rules follow the standard single-storey rear extension framework:

• Permitted development: Extensions up to 3 metres (semi/terraced) or 4 metres (detached) beyond the original rear wall can proceed without planning permission
• Prior approval (larger home extension scheme): Extensions up to 6 metres (semi/terraced) or 8 metres (detached) require prior approval notification to the council
• Full planning permission: Extensions beyond these limits, or in designated areas, require a planning application

The internal wall removal element does not require planning permission in itself — this is a structural matter handled through building regulations rather than the planning system.

Structural Requirements

Steel Beams for Wall Removal

Removing load-bearing internal walls to create an open-plan layout requires structural steel beams to carry the loads from the floors, walls, and roof above. A structural engineer must calculate the beam sizes and produce stamped calculations for building control. Typical beam installation costs range from £1,500–£5,000 per wall opening depending on size and load.

Rear Wall Opening for Bifold Doors

Creating a large opening in the rear wall for bifold or sliding doors also requires a structural steel beam above the opening. For a 4–5 metre opening, this beam alone may cost £3,000–£6,000 to supply and install correctly. The beam size is critical — an undersized beam will deflect over time, causing the doors to jam and the wall above to crack.

Column and Frame Structure

For open-plan extensions with multiple wall removals and large rear openings, the structural engineer may design a frame of columns and beams rather than individual point loads. This is more complex and expensive but creates a genuinely column-free open-plan space.

Bifold Doors vs Sliding Doors for Kitchen Extensions

The choice of rear glazing significantly affects both the look and the budget of the extension:

Factor	Bifold Doors	Sliding Doors
Opening width (typical)	Up to 7m+	Up to 6m+ with multiple panels
Opening area when open	Near-full width	50% (panels stack behind each other)
Frame sightlines	More frame due to folding mechanism	Slim sightlines on quality systems
Cost (3m opening)	£3,000–£8,000	£3,500–£9,000
Maintenance	More hinges and seals	Less maintenance

Design Considerations for Open-Plan Kitchen Extensions

Natural Light

North-facing rear extensions receive less direct sunlight. Compensate with rooflights over the kitchen area, a side lantern, or a fully glazed rear wall. Even south-facing extensions benefit from overhead glazing to bring light deep into the interior.

Kitchen Island Positioning

An island unit defines the transition between kitchen and living zones without creating a visual barrier. Position it to allow clear sightlines from the cooking area to the dining table and garden doors — particularly useful for families with young children.

Acoustic Zoning

Fully open-plan spaces allow noise to travel freely. Consider subtle level changes, half-height partitions, or acoustic ceiling treatments to create zones without closing off the space. Underfloor heating (rather than radiators) keeps walls clear and supports the open aesthetic.

Underfloor Heating

Underfloor heating (UFH) is almost universal in new kitchen extensions because it frees up wall space, produces even warmth, and works efficiently with the large glazed areas typical in these extensions. Wet UFH (connected to the boiler) costs more to install (£80–£120/m²) but is cheaper to run than electric systems.

Frequently Asked Questions

How much does it cost to remove a load-bearing wall as part of a kitchen extension?

Removing a load-bearing wall as part of an extension project typically costs £2,500–£5,000 per wall (including structural engineering fees, temporary propping, steel beam, padstones, and making good). If multiple walls are being removed simultaneously, there is some economy of scale.

Do I need planning permission to open up my kitchen into an extension?

The internal wall removal element does not require planning permission. The extension itself may or may not require planning permission depending on its size and location. Your architect will confirm what approvals are needed.

How deep should a kitchen extension be?

A depth of 3–5 metres is typical for a rear kitchen extension. This is enough to accommodate a generous kitchen with an island, a dining area, and a small seating zone. Deeper extensions (6m+) suit larger families wanting separate cooking, dining, and living zones in a single open space.

Can I install bifold doors in an existing rear wall without an extension?

Yes — creating a new opening in the rear wall for bifold or sliding doors does not require planning permission in most cases (it is an internal change and an alteration to the rear wall). Building regulations approval is required for the structural steel beam above the new opening.

Will an open-plan kitchen extension add value?

Yes — significantly. Open-plan family living spaces are consistently cited as one of the top priorities for UK homebuyers. A well-designed kitchen extension typically adds 10–20% to property value in most UK regions, with higher uplift in London and the South East.

Start Planning Your Kitchen Extension

Crown Architecture & Structural Engineering designs open-plan kitchen extensions across the UK. We provide architectural design, structural engineering, planning applications, building regulations, and project management in one fixed-fee package.

Call 07443804841 or complete the enquiry form above to arrange a consultation.