Kitchen Extensions

What Is a Kitchen Extension?

A kitchen extension is a rear or side extension specifically designed to create a larger kitchen, an open-plan kitchen-diner, or a combined kitchen-living space. It is the most popular type of home extension in the UK because it transforms the most-used room in the house and adds significant value to the property. A typical kitchen extension involves removing part of the existing rear wall, extending outward by 3–6 metres, and creating a single open-plan space that flows from the kitchen into a dining and living area. Large glazed openings — bi-fold doors, sliding doors or full-width corner windows — connect the new space to the garden, bringing in natural light and creating a sense of openness.

Kitchen Extension Costs

A kitchen extension typically costs between £40,000 and £80,000 depending on size, specification and the level of internal finish. The build cost (shell, structure, roof, electrics, plumbing and decoration) usually accounts for around 60–70% of the total budget, with the kitchen itself — cabinets, worktops, appliances and fitting — making up the remainder. Key cost drivers include the span of structural steelwork needed to create the open-plan layout (typically £2,000–£5,000), the type of glazing (aluminium bi-fold doors cost £3,000–£8,000 per opening), and whether underfloor heating, roof lanterns or vaulted ceilings are included. Professional fees for drawings, structural engineering and planning add 10–15%.

Planning and Permitted Development

Many kitchen extensions fall under permitted development rights, particularly single storey rear extensions up to 3 metres deep (6 metres with a prior approval notification for detached houses, 4 metres for semi-detached). Extensions that exceed these limits, are within 2 metres of a boundary and over 3 metres high, or are on properties in conservation areas will need full planning permission. All kitchen extensions require building regulations approval covering structural safety, drainage, ventilation, thermal performance and electrical installation. MTD Building Contractors advise on the best route during the initial consultation and handle all submissions.

Design and Specification Options

The most popular kitchen extension layout is an L-shaped or linear design with a central island, bi-fold or sliding doors across the rear elevation, and a roof lantern or flat rooflight above the dining area. Flooring options range from engineered hardwood and porcelain tiles to polished concrete. Underfloor heating (wet system connected to the boiler) is standard in most kitchen extensions and costs £40–£60 per square metre to install. We coordinate with your chosen kitchen supplier and fitter, or can recommend trusted partners, to ensure the kitchen installation integrates seamlessly with the building work.

Timeline for a Kitchen Extension

A typical kitchen extension takes 10–16 weeks on site from groundworks to handover. This includes foundations and drainage (1–2 weeks), walls and structural steelwork (2–3 weeks), roof and weatherproofing (1–2 weeks), first fix electrics and plumbing (1–2 weeks), plastering and screeding (1 week), second fix and decoration (2–3 weeks), and kitchen installation (1–2 weeks). Allow 6–10 weeks before construction for design, planning and building regulations. The total project timeline is typically 5–7 months from first enquiry to completion.