What Drives Kitchen Extension Cost
A kitchen extension is two projects wearing one name. There is the building work, and there is the kitchen. They are priced by different trades, have different lead times, and overrun for entirely different reasons. Almost every kitchen extension that goes wrong financially does so because those two budgets were treated as one.
Splitting the two budgets
Write them as separate lines from day one: shell and structure in one, kitchen and fit out in the other. The shell is largely fixed by the site and the design. The fit out is almost entirely your choice, and it can vary several fold for the same floor area.
Once split, trade offs become visible. Knowing exactly what the island costs against a wider rooflight is a decision. Discovering it at second fix is a compromise.
Services, decided early or paid for twice
Kitchens are the most services heavy room in a house. Every appliance position implies a power supply, a water feed, a waste route or an extract path, and all of them are cheap to move on a drawing and expensive to move once the floor is down.
Extraction route to an external wall, which drives the hob position · Waste falls for a sink in an island, which the floor build up has to accommodate · Circuits for ovens and induction hobs, and whether the consumer unit can take them · Underfloor heating zoning and where the manifold lives · Boiling water taps and integrated appliances needing dedicated supplies
Light, and what it costs
Deep rear extensions are dark in the middle unless light comes from above. Rooflights are the most cost effective fix and structural glazing the most expensive, and the choice between them changes the feel of the room more than any finish will.
Glazing decisions also interact with heating. Large areas of glass need thinking about for both summer overheating and winter comfort, which is a specification conversation rather than an afterthought.
Where the old kitchen was
The new kitchen usually goes into the new space, which leaves the old kitchen as a room needing a purpose, a floor, and a decoration. That is real work and it belongs in the scope.
Equally real is living without a kitchen during the build. A temporary kitchen somewhere else in the house is worth budgeting for in both money and patience, and its duration should be a stated part of the programme.
Sequencing that saves money
Choose the kitchen before first fix, not after. The supplier's technical drawing is what tells the electrician and plumber where everything goes, and having it in hand at first fix avoids the single most common source of rework on these projects.
Made to measure kitchens and stone worktops also carry lead times measured in weeks, with worktops usually templated only after the units are installed. Building that into the programme prevents a finished room sitting unused.
Frequently asked questions
Should the builder supply the kitchen?
Either works. What matters is that responsibility for the technical drawing, the appliance schedule and the installation is unambiguous, because that is where disputes start.
When do I need to choose the kitchen?
Before first fix. The layout dictates every service position, and changing it afterwards means opening up work that has already been paid for.
How long without a kitchen?
It varies with the design, and the honest answer comes from the programme rather than a general rule. Ask for it as a specific date range and plan a temporary setup around it.
Is an island always possible?
Not always. An island with a sink or hob needs waste, power and extraction crossing the floor, so it has to be designed in before the slab and the floor build up are fixed.
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