Kitchen Extensions London

A kitchen extension in London is a building project and a kitchen project that have to be planned in the right order. The room at the back of the house is single storey, and the kitchen inside it decides where the drains, the extract duct, the power and the glazing go. If you are weighing up a rear, side return or wraparound kitchen extension before anyone draws it, this page is written for you. It covers which London houses suit which shape, how the job runs while the old kitchen stays in use, the consents and who applies for each, and what the published London ranges say it costs. We write as the contractor who builds the room and fits the kitchen in it. The foundations and steel are designed by the structural engineer we appoint, building control inspects the work, and any party wall notices are yours to serve.

Across London, a rear kitchen extension of about 30 square metres typically costs £45,000 to £97,500 excluding VAT, or £60,000 to £100,000 for a side return (indicative ranges, Resi, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in London: the structural engineer we appoint designs the foundations and steel, we build the room and fit the kitchen, and a registered electrician certifies the electrics.

Which London homes suit a kitchen extension, and which shape?

The kitchen you have now usually points to the extension you need. In a Victorian or Edwardian terrace the kitchen sits in the back addition, a room barely wider than one run of units, with a shaded yard beside it. Building into that yard puts the table next to the cooking instead of in another room, which is why the side return is the commonest London kitchen extension. With a deep enough garden, the new room can also run past the back addition as a wraparound. Our side return and wraparound extension pages cover each shape. In a 1930s semi the kitchen already sits at the back beside the side passage, so a full-width rear room, sometimes turning into the passage for a utility, is the usual answer.

Post-war houses usually have a small kitchen on a concrete floor behind a plain cavity wall, which keeps the building side of the job simpler than on older stock. A detached house can put the new kitchen wherever the garden gets the best light, with the drain run as the main limit. Flats are the hard case. Only a ground floor flat with a garden of its own can build out, and then only with planning permission and the freeholder's consent, so many flat owners are better served by a kitchen renovation inside the existing walls. In a house, a kitchen-led extension is the right tool when the kitchen is the one room short of space. If the whole ground floor needs replanning, start with the house layout instead.

How a London kitchen extension runs, with the old kitchen still in use

The kitchen is designed first, and that is the difference from other extensions. An architect or designer you appoint draws the room, and the kitchen plan is fixed at that stage, because the sink waste, the island feeds and the extract duct all run in or under the new slab. The structural engineer we appoint then designs the foundations and the steel to suit that plan, including whether the beam can sit flush so wall units fit beneath it. Before anything is dug, the drains are surveyed by camera and any build over agreement is in place. On site we dig the foundations, pour them once building control has seen the trenches, lay the drainage, and cast the slab with the kitchen's ducts and waste already in it.

The walls and roof go up while you keep cooking in the old kitchen behind the existing rear wall. The boiler flue, the soil pipe and any airbricks on that wall are moved before the new room closes around them, and the gas meter stays reachable. Only when the shell is weathertight is the rear wall opened on its steel and the old kitchen taken out. First fix follows: the hob and oven circuits, the waste runs, the duct to outside, and the gas to the hob by a Gas Safe registered engineer. Underfloor heating and screed go down, and the screed is given time to dry. Plaster, units, worktops and the floor finish follow, a registered electrician certifies the electrics, and building control issues the completion certificate.

Which consents does a London kitchen extension need?

Most London kitchen extensions need building regulations approval and either permitted development or a planning application, and many also need party wall notices and a build over agreement for a shared drain. On a house, a single-storey rear kitchen extension is often permitted development if it stays within the limits on projection, height and eaves height near the boundary, measured from the house as first built. A side return infill counts as a side extension, with its own height and width limits, and a wraparound must satisfy both sets, which many do not. Your architect or designer makes any application. A conservation area removes side extension rights, a listed house needs listed building consent, and flats have no householder permitted development at all.

Building regulations apply to every kitchen extension, whatever the planning route. Approved Document A covers the foundations and the steel, Part L the insulation and the glazed area, Part F the cooker extract, Part H the new drainage and Part P the kitchen circuits. The glazed area matters most in a kitchen. A glass roof plus a wall of sliding doors can exceed what Part L allows unless the rest of the design compensates, so it is checked before the doors are ordered. Where the new room is dug within three metres of a neighbour's building and below their foundations, built on the line of junction, or has steel bearing into the shared wall, the Party Wall etc. Act 1996 applies. You serve those notices as building owner, and we supply the drawings they rely on.

What does a kitchen extension cost in London?

A ground floor rear kitchen extension of about 30 square metres in London costs £45,000 to £97,500 excluding VAT, from the low end for an individual contractor to the high end for a large company. A side return runs £60,000 to £100,000 and a wraparound £80,000 to £130,000, the London ranges used across this site (MyBuilder and Checkatrade, 2026). Those are Resi's London figures for 2026. Side return building work in London runs £2,400 to £3,200 per square metre of new floor, and a new kitchen within it £5,000 to £14,000, a UK figure (Checkatrade, 2026). Resi puts a structural engineer at £950 to £2,500. These are indicative ranges, not a quotation, and a firm price follows our survey and the engineer's design.

The spread in those ranges comes less from the size of the room than from what the kitchen asks of the building. A sink near the existing drain costs little to connect, while an island sink needs a waste cast into the slab with a fall to a new chamber. A hob on an outside wall can vent straight through it, while a hob on an island needs a ceiling extractor and a duct across the roof void. Moving a boiler, diverting a shared drain and choosing a glass roof over rooflights each add real money. The layout has to be fixed early, but the doors, the worktop material and the appliances can be chosen later without changing the building. That is where you control the final figure.

Living in a London house while the kitchen extension is built

You can usually stay at home, and the right sequence means you lose the kitchen for weeks rather than for the whole job. The old kitchen keeps working while the foundations, walls and roof go up outside it, so the gap runs from the day the rear wall is opened to the day the new sink and hob are connected. Set up a temporary kitchen before that day: a kettle, a microwave, a fridge and a sink with hot water, ideally in a room with its own door. Expect the garden to be a site for the whole job. A sealed dust screen across the opening keeps the rest of the house usable while the plastering and fitting are done.

Access decides much of the programme on a London kitchen extension. On a mid-terrace with no side way, every bag of spoil and every block passes through the house, so that route is protected before the groundworks begin. The kitchen units arrive the same way at the end. Neighbours feel this work more than most, because it is built on or near their boundary and often below their windows. A letter setting out the programme and the noisy days before the first dig does more than any apology later. Skips and parking bay suspensions need the council's permission. In a ground floor flat, the lease and the managing agent set the working hours and the protection needed for shared entrances and gardens.

What goes wrong with London kitchen extensions, and how to choose a builder

The expensive mistakes on kitchen extensions are nearly all made below the finished floor. An island is drawn after the slab was cast, so its sink has no waste and ends up on a raised plinth or a pump. A hob is placed where no duct can reach outside, leaving a recirculating hood and condensation running down the rooflight. A boiler is left on the old rear wall with its flue now discharging into the new room, which is unsafe and has to be moved late. Airbricks are buried, so the timber floor behind them loses its ventilation. The new floor ends a step below the old one. Wall units will not fit under a downstand beam. Each costs little to get right on paper and a lot in concrete.

Choose a contractor who asks about the kitchen before pricing the building. Ask when the kitchen layout has to be fixed, and what happens if it changes after the slab is cast. Ask whether the steel will sit flush or below the ceiling. Ask whether the price includes moving the boiler, the soil pipe and the gully, the duct to outside, the floor finish through the old opening and making good the old walls. Ask whether the kitchen fit is in the same contract. With us, one named point of contact runs the job from survey to certificate, the work is done by our own trades rather than a subcontractor chain, and building control is coordinated on every notifiable job. If only the kitchen needs replacing, start with our kitchen fitters page.

• Building control inspections from footings to completion
• Rear, side return and wraparound kitchen extensions
• Sliding, bifold and steel-framed glazed doors to the garden

Work in London rarely sits on its own, so you may also want kitchen renovation in London, a wraparound kitchen-diner, how building control inspects an extension and Side Return or Rear Extension.

Why Choose GS Renovation in London

London homeowners choose GS Renovation for a kitchen extension because the room and the kitchen in it are one job for one team. The sink, the duct and the island feeds are fixed before the slab, not worked around afterwards. The structural engineer we appoint designs the foundations and steel, our own trades build the shell and fit the kitchen, a registered electrician certifies the electrics, and building control is coordinated on every notifiable job. Abdelaaziz Saaid, founder and director, has over 30 years of hands-on experience, and a free, no-obligation written quotation follows the survey. You deal with one named point of contact, and we are rated 4.9 from 31 reviews on MyBuilder.

• New floor level matched to the existing house, with no step at the opening
• Free follow-up visit after completion if anything needs attention
• Cooker extract taken outside through the new roof or flank wall, not recirculated

Checked by Abdelaaziz Saaid, founder and director of GS Renovation Ltd (Companies House no. 14611254). Structural design is by the consulting engineer appointed to your project.