How much does a kitchen extension cost?

Budget £55,000–£130,000 total, including the extension build, kitchen units, appliances, and professional fees. The extension itself costs £36,000–£84,000 depending on size; the kitchen fit-out is £10,000–£33,000 on top.

Should I design the kitchen or the extension first?

Design them together. The kitchen layout determines where services (water, gas, electrics) need to go, which affects the structural design. We design the extension and kitchen layout as one integrated project.

What size kitchen extension do I need?

For a kitchen-diner with an island, you need at least 4.5m width and 5m depth (22.5m²). For a simpler layout without an island, 4m x 4m (16m²) works well. We help you determine the right size based on your property and how you cook and eat.

Can I relocate the kitchen to the extension?

Yes. Many homeowners move the kitchen into the new extension and repurpose the old kitchen as a utility room, study, or playroom. This gives the best result but costs more because you are fitting out two rooms.

How much does a kitchen extension cost?

Budget £55,000–£130,000 total, including the extension build, kitchen units, appliances, and professional fees. The extension itself costs £36,000–£84,000 depending on size; the kitchen fit-out is £10,000–£33,000 on top.

Should I design the kitchen or the extension first?

Design them together. The kitchen layout determines where services (water, gas, electrics) need to go, which affects the structural design. We design the extension and kitchen layout as one integrated project.

What size kitchen extension do I need?

For a kitchen-diner with an island, you need at least 4.5m width and 5m depth (22.5m²). For a simpler layout without an island, 4m x 4m (16m²) works well. We help you determine the right size based on your property and how you cook and eat.

Can I relocate the kitchen to the extension?

Yes. Many homeowners move the kitchen into the new extension and repurpose the old kitchen as a utility room, study, or playroom. This gives the best result but costs more because you are fitting out two rooms.

Kitchen Extension: Design, Cost & Planning Guide 2026

A kitchen extension is the single most popular home improvement project in the UK. The goal is almost always the same: create an open-plan kitchen-diner-living space that flows to the garden. This guide covers how to get there — from the first sketch to the finished room.

Fixed prices, no surprises

Local team in Poole

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48-hour delivery

Based in Poole since 2017

What you need to know

Why extend for a kitchen?

The kitchen is the heart of the modern home, but most British houses were designed with small, separate kitchens. An extension creates the open-plan layout that buyers, families, and estates agents all value. A well-designed kitchen extension transforms how you live and typically adds 5–10% to your property value.

Choosing the right layout

The five most effective kitchen extension layouts are: island kitchen (needs 4.5m+ width), galley with a view, L-shape with peninsula, broken plan (partial walls for zones), and front-to-back open plan (for terraces). We design layouts specific to your property and how you use the space.

Kitchen vs extension budget

The extension (structure, foundations, roof, windows) and the kitchen (units, worktops, appliances) are separate budgets. A common mistake is spending everything on the build and having nothing left for a decent kitchen. We recommend allocating 20–30% of the total budget to the kitchen fit-out.

How much does it cost?

Item	Typical Cost Range
Extension build (20–30m²)	£36,000–£84,000
Kitchen units and worktops	£8,000–£25,000
Appliances	£2,000–£8,000
Bi-fold or sliding doors	£3,000–£8,000
Underfloor heating	£2,000–£4,000
Professional fees	£2,000–£5,000
Total project budget	£55,000–£130,000

Prices based on Dorset rates, 2026

Planning permission

Most kitchen extensions fall under Permitted Development (up to 4m/8m rear projection). However, if you want a larger extension, a wrap-around, or your property is in a designated area, you will need planning permission.

Standard PD rules for rear extensions apply. The kitchen layout, worktops, and appliances do not affect planning — only the external dimensions of the extension matter for PD compliance.

Building regulations

Standard Building Regulations for extensions apply. Additional considerations for kitchens: adequate ventilation (extraction over the hob), drainage for sinks and dishwashers, electrical certification for new circuits, and gas safety certification if relocating the boiler.

Typical timeline

Phase	Duration
Design (extension + kitchen layout)	3–4 weeks
Planning (if required)	0–8 weeks
Extension build	10–16 weeks
Kitchen installation	2–3 weeks
Finishing	1–2 weeks

Frequently asked questions

Related extension types

Single Storey Rear Extension: Complete Guide 2026 Side Return Extension Guide: Costs, Planning & Design 2026 Open-Plan Living Guide: Wall Removal, Costs & Design 2026 Wrap-Around Extension Guide: Cost, Planning & Design 2026

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