Why combine extension and kitchen as one project
The structural and fit-out phases of a kitchen extension are deeply interdependent. Plumbing positions determine sink and appliance locations. Steel beam positions determine where you can place a breakfast bar or island without blocking flow. Underfloor heating zones map to kitchen layout zones. Gas, water and electrical routes set out from the meter point in the original house connect to positions that only make sense once the structural frame is decided. Trying to coordinate a builder and a separate kitchen company across these decisions is the single biggest source of cost overruns and delays in London kitchen extension projects. We handle both in-house: our project manager owns the full programme, the kitchen supplier sits under our main contract, and any design change ripples through the build spec and the kitchen layout at the same time. Our kitchen extension clients consistently report that the integration is the biggest practical benefit of working with us — not just price or quality.
Extension type and kitchen layout
The most common kitchen extension type in London is the side return — filling the narrow alleyway alongside a Victorian terrace's rear closet wing to widen the kitchen by 3–4 metres. This gives an island layout with the kitchen run against the new side wall, island running parallel down the centre, and bifold or sliding doors connecting the dining zone to the garden. The second most common is a rear extension (3–6m deep) used to extend and relocate the kitchen into a larger open-plan space. Wraparounds combine both and deliver the largest kitchen possible on a Victorian terrace. On detached and semi-detached homes a double-storey extension can add a bedroom above while extending the kitchen below. We assess which option delivers the most usable kitchen at survey and present two or three layout options with indicative costs before any commitment.
Kitchen specification and suppliers
Our kitchen package covers everything from island carcass to handles — we supply and install, not just build the shell. For mid-range kitchens (£15,000–25,000 kitchen budget) we work with Roundhouse, Harvey Jones and DesignSpace London. For premium kitchens (£25,000–60,000+) we work with Bulthaup, Smallbone, Plain English and Dinesen for worktops. For budget-conscious projects where the structural build is the priority, we can supply and install a fitted Neff-appliance IKEA or Howdens kitchen — still to a high finish standard because our fitters handle both structural work and cabinet installation, so tolerances and levels are exactly right. Every kitchen quotation includes units, worktops, appliances (hob, oven, extractor, fridge, dishwasher, sink), taps, and installation. Appliance upgrades (wine cooler, steam oven, induction hob) are priced as a PC schedule so you know exactly what each upgrade costs before choosing.
Bifold doors, sliders and glazing
The rear wall of a kitchen extension is typically 80–100% glazed. Bi-folding doors (3–5 panel typical across a 3–5m opening) allow the wall to fully open in summer — the threshold drops flush to allow indoor-outdoor flow. Sliding doors offer larger individual glass panes and slightly better thermal performance. Crittall-style steel-framed doors are the premium option — slimmer frames, more architectural character, roughly 40–60% more expensive than aluminium bifolds. All glazing is double or triple with low-e coating and argon fill. We supply Origin, Schüco and Sunflex systems depending on budget and specification. Roof lanterns are standard on flat-roofed extensions; we use Korniche and Brett Martin units. Most clients choose a 3m × 1m or 3m × 1.5m lantern to wash natural light across the kitchen island.
Structural approach
The key structural move in most London kitchen extensions is removing the existing rear or side wall to open the new extension to the original kitchen. This requires a steel beam (typically 203–305 UC or UB, sized to span) spanning the full width of the opening, sitting on padstones on the existing walls. For a side return, an additional beam picks up the closet wing roof above the opening. Foundations follow the extension type: side returns often run along the boundary wall using strip foundations to 1m depth; rear extensions use mass-fill concrete strips. On London clay near mature trees we assess tree species, distance and spread against NHBC guidance and specify deeper or piled foundations where movement risk requires it. Building regulations apply throughout — structural calculations, building control inspections, and a final completion certificate are all included in our fixed price.
Planning routes
Most single-storey kitchen extensions can proceed via permitted development. The standard PD envelope allows a single-storey rear extension up to 3m depth on a terrace or semi. The Larger Home Extension prior approval scheme extends this to 6m on terraces and semis, and 8m on detached homes — a 21-day neighbour consultation followed by automatic approval if no objections are received. Side returns filling the alleyway to the boundary typically fall under Class A PD. Wraparounds almost always require full planning because combined volume and depth exceeds PD limits. Conservation areas and Article 4 directions (much of Hackney, Islington, Camden, Westminster and Hammersmith) remove PD rights and require full planning applications. We run a free desk-based planning assessment on every quote so you know the exact route before signing.
Disruption and programme
The existing kitchen is unavailable from week one. We install a temporary kitchen (microwave, fridge, induction hob, electric kettle, sink if structurally possible) in the front lounge or dining room before demolition starts. The temporary kitchen runs for the full build duration — typically 10–16 weeks depending on extension type and kitchen complexity. Families tell us this is the most disruptive aspect of a kitchen extension, not the noise — we acknowledge that and set up the temporary kitchen before the first demolition hammer swings. Major noise phases are weeks two through four (demolition, foundations, steelwork) — we schedule these Monday to Friday between 8am and 6pm and always give advance notice before the noisiest operations. The extension is usually watertight by week six and the temporary kitchen stays until the new kitchen is commissioned.
