Dreaming of a big open plan kitchen where the whole family can cook, eat and relax together. An extension can change the way you live in your home.
On this page you’ll find the different types of extension, the drawings and approvals you need, exactly how we build it from the foundations to the final finish and how we look after you along the way. Use our extension planner below and send us your details in under 5 minutes.
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The short answer: Most single storey extensions take 10 to 14 weeks on site depending on the size the ground conditions and the finish. The new space is built outside first so you can usually stay at home and every extension we build comes with our 10 year warranty.
Extension planner
Tell us a little about your home and what you’d like in your new space. We’ll come back to you with a free site visit and a clear written quote.
Tap an extension type and watch it grow out of the back of the house. Drag the house to turn it around, then tap Before and After to compare your home today with your new space.
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Your home todayYour new extensionGlass
Built out from the back of the house into the garden. It’s the most popular way to create one big open plan kitchen, dining and living space with bi fold or sliding doors opening straight onto the garden.
Many Victorian and Edwardian terraces have a narrow alley down the side of the back addition. We build into that space so a narrow galley kitchen becomes a wide, bright room, often with a glass roof along the side.
A side return and a rear extension built together in one L shape. It gives you the biggest open plan room of all and it’s the classic London kitchen extension.
Adds space on the ground floor and the first floor at the same time, for example a bigger kitchen downstairs and a new bedroom or bathroom upstairs, all under one roof.
Your extension
Terraced house, rear extension
Tap the button below and your answers will be sent to us on WhatsApp. Add a photo of the back of your house and garden and your postcode and we’ll arrange your free site visit.
Client reviews
Read what clients say about communication, organisation, care in the home and the quality of the finished work.
Cost
Every extension is different so we price every one individually after a free site visit. Two houses on the same street can need very different work below ground and behind the walls. These are the things that make the biggest difference.
A simple rear extension costs less per square metre than a wraparound, which has more walls, more steel and a more complex roof.
London clay, nearby trees and old drains can mean deeper foundations or in some cases piles. We check the ground conditions with the engineer before we price.
Opening the back of the house into the new space needs steel beams and sometimes a steel goalpost frame. The bigger the opening the bigger the steel.
Roof lanterns, rooflights a glass side return roof and large bi fold or sliding doors all add light, and cost.
If a public sewer or drain runs where the extension will go it may need protecting, diverting or a build over agreement with Thames Water.
Drawings, structural calculations, planning or prior approval, Building Control, Party Wall surveyors and Thames Water all form part of the overall cost.
Completed projects
Real projects by our team, photographed on completion. Open one to see the scope, the finishes and how the work came together.
Prices
This is what our clients typically pay for a fully finished extension with us in 2026, excluding VAT. Your exact price depends on your foundations, steels, roof and glazing, so we always confirm it in a written quote after a free site visit.
| Extension type | Price per m² | Typical total |
|---|---|---|
| Single storey rear20 m² | £2,800 – £4,000 | £56,000 – £80,000 |
| Single storey rear30 m² | £2,800 – £4,000 | £84,000 – £120,000 |
| Side returnAbout 12 to 15 m² | £3,000 – £4,200 | £36,000 – £63,000 |
| WraparoundAbout 30 to 40 m² | £2,900 – £4,000 | £87,000 – £160,000 |
| Double storeyAbout 40 m² over two floors | £2,400 – £3,400 | £96,000 – £136,000 |
How the price per m² works: It’s the build cost divided by the new internal floor area. Double storey extensions cost less per m² because the foundations and roof are shared across two floors. Side returns cost more per m² because they’re small with glass roofs and party wall work.
Not included in these figures: VAT, architect and engineer fees, planning or prior approval fees, Building Control fees, Party Wall surveyor fees and any Thames Water build over agreement. We’ll show every one of these clearly in your quote.
Not sure what to buy? We’ll help you choose, point you to trusted suppliers and check every item fits before you order.
Extension types
The right extension depends on your house, your garden, your budget and what the council will allow.
Built straight out from the back of the house. Perfect for semi detached and detached homes and modern terraces where the back wall is flat.
Fills the narrow alley beside the back addition of a Victorian or Edwardian terrace. It turns a narrow galley kitchen into a wide, bright room.
A side return and rear extension combined into one L shaped space. The biggest open plan room you can build on one floor.
Adds a room downstairs and a room upstairs at the same time, usually a bigger kitchen and an extra bedroom or bathroom.
Many clients combine an extension with a loft conversion. One scaffold, one team and one programme for the whole house.
That’s what the free site visit is for. We’ll look at your house and garden and explain which options will work best.
Planning and approvals
Every extension needs proper drawings and approval before any work starts. This is the part most homeowners worry about, so we take care of it for you from start to finish. Here’s exactly what’s needed at each stage and what we do for you.
What’s needed: A measured survey of your house and garden and a full set of drawings showing the existing and proposed floor plans, elevations, sections and site plan. The council, Building Control and the structural engineer all work from these drawings.
How we help: We arrange the survey and the architect and make sure the drawings show exactly what you want and exactly what we’ll build.
What’s needed: A structural engineer designs the foundations, steel beams, padstones, lintels and roof structure and provides calculations for Building Control.
How we help: We work with the engineer so the design is safe, practical to build and good value.
What’s needed: Before work starts your extension needs approval from the council in one of three ways.
How we help: We tell you which route your extension needs, prepare the application with the architect, submit it to the council and deal with any questions from the planning officer.
What’s needed: Every extension needs Building Regulations approval through a full plans application or a building notice. Building Control inspects the foundations, drainage, damp proofing, structure and insulation as the work goes on and issues a completion certificate at the end.
How we help: We submit the application, book every inspection and hand you the completion certificate when your extension is finished.
What’s needed: Under the Party Wall etc. Act 1996 you must serve notice on your neighbours at least one month before digging foundations within 3 metres of their foundations, and at least two months before building on or cutting into a party wall.
How we help: We help you prepare the notices, talk to your neighbours and work with the party wall surveyor if one is needed.
What’s needed: If your extension will be built over or within 3 metres of a public sewer you’ll need a build over agreement from Thames Water before work starts.
How we help: We check the sewer records and run a drain survey where needed, then help you apply and protect the drains during the build.
Our promise: We never start work until every drawing and approval is in place. It protects you, your home and your neighbours and it means all your paperwork is ready when you come to sell.
Foundations, steel beams and the roof designed by a structural engineer to carry every load safely.
A damp proof course in the walls and a damp proof membrane under the floor to keep moisture out.
Background ventilation through trickle vents and an extractor over the hob to the outside.
New drains, gullies and inspection chambers laid to the right falls, with existing drains protected or diverted.
Insulated walls, floor and roof. Glazing is normally limited to 25 per cent of the new floor area plus the area of any windows and doors removed. More glass is possible with an energy calculation showing the rest of the extension makes up for it.
New circuits installed and certified by a registered electrician.
Our process
From the first site visit to the final sign off you deal with one team, and the people who quote your extension are the people who build it.
We look at your house, the back wall, the garden, the drains and any trees nearby. We’ll talk about how you want to use the new space and explain which type of extension will work best.
The architect and engineer prepare the drawings and calculations and we take care of the applications and notices. You get a clear itemised quote showing what’s included, what isn’t and how long each stage will take. Nothing extra is ever added without your approval in writing.
We protect your home, set up a secure site area and arrange skips, deliveries, usually through the side or rear access so your house stays clean.
We dig the foundations, usually trench fill concrete, to the depth set by the engineer and agreed with Building Control. In London clay and near trees they can be 2 metres deep or more. Building Control inspects the trenches before the concrete goes in.
New drains and gullies are laid and tested. Then the floor goes in with a damp proof membrane, insulation and a concrete slab.
We build the cavity walls with blockwork inside, brickwork outside to match your house, cavity insulation, wall ties and a damp proof course.
The steel beams go in on padstones, then the roof: Usually a warm deck flat roof finished in EPDM rubber or GRP fibreglass with a roof lantern or rooflights. Once the new space is weathertight we take down the back wall of the house and open everything up.
Bi fold or sliding doors and windows are fitted, then plumbing, electrics and underfloor heating pipes go in.
The floor is screeded and left to dry properly, a traditional sand and cement screed needs around a day per millimetre. Walls and ceilings are plastered and then your kitchen is fitted.
Flooring, second fix electrics, decoration and a deep clean. Building Control issues your completion certificate and we walk round with you and check every detail before we sign off. You’ll receive your electrical certificate and your 10 year warranty in writing.
Timeline
Most single storey extensions take 10 to 14 weeks on site. Here’s how a typical rear extension runs:
Protection, excavation and concrete.
Drains, floor slab, blockwork and brickwork.
Steel beams, roof structure, roof covering and lantern.
Back wall removed, doors and windows fitted, plumbing, electrics and underfloor heating.
Screed drying, plastering, kitchen, flooring, decoration and sign off.
Wraparound and double storey extensions take longer. We’ll give you a full programme with your quote.
Tips
Your kitchen layout decides where the drains, sockets, lights and steels need to go. Bring your kitchen designer in at the drawing stage.
A roof lantern over the kitchen island and rooflights along a side return make an extension the brightest room in the house.
It keeps a big open plan room warm without radiators on the walls, leaving more space for cupboards and glass.
Reclaimed or carefully matched bricks make the extension look like it’s always been part of the house.
Level thresholds and matching patio tiles inside and out make the kitchen and garden feel like one space.
Party Wall notices and prior approval both involve your neighbours. Speaking to them early keeps things friendly and avoids delays.
Director London’s Prestige
I look after every project personally. From the first visit to the day we hand over you deal with me and my own team not a middleman. If you ever have a question, just pick up the phone.
We build every extension to last, from the foundations hidden in the ground to the finish you see every day. That’s why every extension we build comes with our 10 year warranty on our work. It’s set out in writing with your quote so you know exactly what’s covered from day one.
Accreditations
We’re members of some of the UK’s leading building organisations. Membership means our business has been checked and approved so you can be confident you’re in safe hands.
Our own team from start to finish.
Drawings, engineers, approvals, Party Wall, Thames Water and the build.
A 10 year warranty on every extension.
NFB Full Member, NABC member.
Clear, itemised quotes, agreed in writing.
Five star reviews on Google.
Free site visit
Send us your postcode and a photo of the back of your house and garden. We’ll call you back, arrange a free site visit and send you a clear written quote.
Prefer to talk now? 020 3576 7307
Areas we serve
We work right across London, north, south, east and west. Wherever your home is, send us your postcode and a few photos and we will be in touch.
London’s Prestige, 41A Mill Lane, London NW6 1NB · Get directions
FAQs
Can’t see your question? Call 020 3576 7307 or message us on WhatsApp.
Yes, most clients do. The extension is built outside first and the back wall is only opened up once the new space is weathertight. Your kitchen will be out of use for part of the build so we’ll help you plan a temporary kitchen.
It depends on the soil and any trees nearby. The engineer sets the depth and Building Control checks the trenches before the concrete goes in. In London clay near trees they can be 2 metres deep or more.
Yes. Glazing is normally limited to about 25 per cent of the new floor area, but more is possible with an energy calculation and good insulation elsewhere. We’ll help you get the light you want and still pass Building Regulations.
We check the sewer records and survey the drains. Private drains can be diverted or protected and public sewers need a build over agreement from Thames Water, which we help you arrange.
A bigger open plan kitchen and living space is one of the most popular ways to add space and value to a London home.
Yes. Every extension we build comes with our 10 year warranty set out in writing.
