How much does a kitchen extension cost?

A kitchen extension combines new construction with work to an existing property and the specification of a working interior. Its cost can depend on the proposed form, site constraints, structural design, openings, services, kitchen installation and the work retained or changed elsewhere in the house.

No numeric range is published here because the authoritative sources reviewed do not provide a current public kitchen-extension average with a consistent region, scope, specification and schedule of inclusions. A project-specific brief and quotation are more reliable than a broad figure that cannot show what has been counted.

The ONS Construction Output Price Indices methodology describes UK-wide indices for changes in construction output prices. The data is aggregated and is not a quotation for a particular kitchen extension. BCIS describes specialist cost data for existing buildings, but its public product information does not establish a transparent homeowner range for this precise project type.

Cost planning should start with the complete scope rather than a single floor-area comparison. Relevant factors may include:

• Existing propertyThe retained construction, known condition and information available for design influence the assumptions that can be made.
• Extension formFootprint, height, roof form and the relationship with the existing house define the proposed construction.
• Structure and openingsFoundations, supports and changes to existing walls require project-specific design and pricing.
• Glazing and external doorsThe dimensions, arrangement and specification of openings form a distinct part of the scope.
• Kitchen specificationCabinetry, worktops, appliances and associated installation need clear boundaries and selections.
• ServicesPlumbing, heating, ventilation, lighting and electrical requirements should be coordinated with the room layout.
• Interior finishFlooring, decoration, fitted storage and junctions with retained rooms affect the completed space.
• Access and sequencingWorking space, protection, deliveries and occupation of the house can influence how the work is organised.

The proposed extension and the retained house need to be considered together. Ground information, existing construction, drainage, concealed services and the size of any new opening can all affect the developed scope.

These matters require appropriate project-specific investigation and professional input. An early allowance should record what information it relies on, what remains unknown and which work would be valued separately if the assumptions change.

For a broader view of foundations, structure and other extension cost drivers, see the house extension cost guide.

Windows, external doors and roof glazing influence the appearance, daylight and connection with outside, while also forming measurable supply and construction items. The opening sizes, frame arrangement, glass specification, thresholds and surrounding work need to be described before proposals can be compared.

Bi-fold doors, sliding doors and roof lanterns are possible choices rather than standard inclusions. Their relevance and technical requirements depend on the individual design; this guide does not recommend one arrangement over another.

Cabinetry, worktops and appliances can be included within one appointment, supplied directly by the client or divided between different parties. The quotation should state that boundary and identify who is responsible for dimensions, coordination, delivery, installation and connections.

An island is one possible layout element, not a default component. Its size, function and relationship with circulation and services should be resolved through the kitchen extension design before associated items are treated as fixed.

Explore bespoke kitchens for the relationship between cabinetry, practical use and the surrounding room.

The intended positions of sinks, appliances, lighting and controls help define the required services. Changes to heating, ventilation, plumbing and electrical systems should be assessed for the particular property by appropriately appointed people.

Underfloor heating is a possible project choice, not an assumed inclusion. Whether it forms part of a proposal, and the related preparation, controls and floor build-up, should be made explicit rather than inferred from the room description.

Flooring may extend through the new kitchen, connect with retained rooms or stop at a defined threshold. The substrate, transitions, skirtings and making-good should be identified alongside the selected finish.

A lighting plan can affect fittings, switching, controls and electrical work. Decoration, ironmongery and final junctions also need clear scope. Taken together, these details determine whether a quotation covers the shell, a partially finished room or the intended complete interior.

Fitted seating, media cabinetry, shelving or storage can be considered where they support the room and its use. They should be described as separate elements, with their design and finish coordinated with the kitchen and surrounding architecture.

These are possible additions rather than standard kitchen-extension inclusions. Where relevant, their design information, installation and interfaces should be visible in the budget. See the broader Bespoke Joinery & Interiors expertise.

A construction quotation covers the work described by that contractor. The complete project budget may also need to recognise surveys, professional appointments, statutory applications, kitchen supply, appliances, direct client purchases and work commissioned separately.

Keep these categories distinct and identify applicable tax rather than assuming every project-related item sits within one total. This makes omissions easier to find and avoids comparing a construction-only proposal with a more complete project estimate.

A rear kitchen extension can change the connection between the existing rooms, the new interior and the garden. Cost is shaped by the actual proposal: the opening into the house, extension form, external openings, services and work required within retained areas.

The label describes a location in the plan, not a fixed package or price. A rear kitchen extension should therefore be costed from its developed information rather than by transferring a figure from a different property.

Early kitchen extension ideas often test how the room might be used as well as how it might look. Possible choices include an island, fitted seating, roof glazing, wide external doors, a utility area or additional fitted storage.

Each option can affect more than the item itself: room layout, structure, services, lighting, flooring or adjacent work may also change. Treat alternatives as priced options until the brief is resolved, rather than allowing them to remain implicit within a headline budget.

Kitchen extension design brings together the extension envelope, circulation, cabinetry and services. Decisions made in one area can alter another, so drawings, specification and responsibilities should develop together.

A disciplined sequence helps distinguish the essentials of the brief from optional elements. It also allows decisions about proportion, material and finish to be reviewed against a visible budget before they become part of the construction scope.

The JP Home Creations five-stage approach sets out how an initial conversation progresses through concept, planning, construction and completion.

Describe how the existing kitchen works now, what the proposed space needs to support and which retained rooms are affected. Gather available surveys, drawings and approval information, and identify any appointed professionals and direct suppliers.

Record confirmed decisions, unresolved questions and optional items. A clear brief should also state whether the desired budget covers only construction or the complete project, including the kitchen and other separately purchased elements.

Issue the same developed information to each suitable contractor and compare the work described, not only the total. Kitchen extension prices are only meaningfully comparable when scope, specification, assumptions, allowances, exclusions and work by others are aligned.

Citizens Advice guidance for homeowners in England recommends obtaining written quotations and agreeing a written contract, and explains the distinction between a quotation and an estimate. Seek appropriate advice where the status or terms of a proposal are unclear.

Identify items described as provisional, client supplied, excluded or dependent on further information. For each allowance, ask what it covers, what information it is based on and how a later selection or change would be reconciled.

Confirm how variations will be described, valued and agreed before related work proceeds. An allowance is not a finished specification, and an item absent from the quotation should not be assumed to be covered elsewhere.

Planning Portal guidance for England explains that some house extensions may be permitted development where relevant limits and conditions are met, while local rules can also affect what is required. The position must be checked for the particular property and proposal.

GOV.UK states that Building Regulations cover the construction and extension of buildings and confirms that Building Regulations approval is different from planning permission. A project may need both; requirements vary across the UK and should be confirmed through the relevant official route.

For a fuller England-focused introduction, read the extension planning permission guide.

Use early budget work to expose missing information and test the brief. As the design develops, replace broad allowances with selections and coordinated scope, while keeping construction cost and the complete project budget clearly distinguished.

Review the wider house extensions expertise or discuss the known property information, intended kitchen extension and current design stage with JP Home Creations.