Thinking of a Kitchen Extension? Here's What You Need to Know

If you've ever stood in a cramped kitchen wishing you could knock through into the garden, you're not alone. A rear kitchen extension is one of the most popular home improvements a UK homeowner can make, and one of the most transformative.

At CNR Construction, we've helped homeowners across Wirral and Merseyside create open-plan kitchen extensions that add real space, light, and value. Here's what you need to know before you start.

Do You Need Planning Permission?

Many rear extensions fall under Permitted Development rights, meaning no full planning application is needed. As a rule, a single-storey rear extension can extend up to 4 metres for a detached house, or 3 metres for a semi or terraced property, without permission.

A few exceptions to be aware of:

• Flats and maisonettes aren't covered by Permitted Development

• Conservation areas and listed buildings have stricter rules

• The extension can't cover more than half your garden

Not sure where you stand? CNR Construction can advise from the first consultation. We know the planning landscape across Wirral and Merseyside well.

How Much Does It Cost?

A rear kitchen extension involves foundations, structural work, brickwork, roofing, glazing, electrics, plumbing, and a full kitchen fit-out, so it's worth being realistic about budget from the start.

As a rough guide for the Wirral area:

• Small extension (3m x 3m): from £20,000–£30,000 for the build

• Medium extension (3m x 4m–5m): typically £35,000–£55,000

• Larger or premium spec extensions: £60,000–£90,000+

• Kitchen fit-out is on top: £5,000 for mid-range up to £30,000+ for bespoke

Build costs generally fall between £1,500–£2,500 per m² depending on specification and any structural complications. CNR Construction provides fully transparent, itemised quotes with no surprises. We have a more detailed pricing guide here.

Structural Work: What to Expect

Most rear kitchen extensions involve opening up the existing rear wall to connect the new space to your home. This typically means installing a steel RSJ beam to carry the load above, which is specialist work that requires Building Regulations approval.

Other structural elements commonly involved:

• Load-bearing wall removal and beam installation

• New foundations for the extension footprint

• Drainage adjustments if required

• Insulation and damp proofing to current standards

CNR Construction handles all of this in-house, including Building Regs sign-off, so you're not left coordinating multiple trades.

Design Ideas

Glazing Bi-fold or sliding doors across the rear create a seamless connection to the garden, while a skylight or roof lantern floods the space with natural light. This is especially valuable in a north-facing plot.

Open-Plan Layout - The most popular approach is combining the kitchen with a dining and family area into one large social space. A well-placed island defines the cooking zone without closing off the room.

Kitchen Layout - More floor space means real layout flexibility. An L-shaped or U-shaped kitchen around an island maximises storage and workflow, and you'll finally have room for features older kitchens rarely allow: a proper pantry, a utility area, or a hob island with a ceiling extractor.

How Long Does It Take?

• A standard 3m–4m extension: 8–14 weeks on site

• Larger or more complex projects: 16–20 weeks

• Add time upfront for any planning or Building Regulations approvals

We give every client a clear timeline from the start and keep you updated throughout.

Why CNR Construction?

We're a Wirral-based team with 11+ years of experience and a 5-star Google rating. We manage every stage of your extension, from groundworks and structural work through to the finished kitchen, with transparent pricing and clear communication throughout.

Covering Wirral, Liverpool, Birkenhead, Heswall, Wallasey, West Kirby, Bebington, and surrounding areas.