Double storey extension in North London
A double storey extension adds room on two floors at once, typically a larger kitchen or living space downstairs and an extra bedroom or bathroom above. As a guide for North London in 2026, prices are around £70,000-£130,000, and because you build both floors together the cost per square metre is often lower than doing two separate projects. Kev Construct builds them across Edgware, North London, Barnet, Enfield and Watford, rated 9.67/10 across 50+ verified Checkatrade reviews.
Recent double-storey extensions
Add space upstairs and down in one build
If your family needs more than the ground floor can give, a double storey extension is the answer. It is the most cost-effective way to add serious space, because the foundations, roof and scaffolding serve both floors. Kev Construct Ltd builds these across North London to a high standard, and we will guide you through every step with clear, honest advice.
What can a double storey extension give you?
Building over two floors lets you solve several problems at once, adding both living space and bedrooms in a single, well-planned project. It is ideal for growing families who need more of everything.
- A larger kitchen or open-plan living space on the ground floor.
- An extra bedroom above, perfect for a growing family or guests.
- An additional or en-suite bathroom, easing the morning rush.
- A more balanced, better-proportioned home that works for years to come.
How long does it take, and do I need permission?
A double storey extension takes longer than a single storey build, because there is more structure, roofing and internal work involved. We agree a realistic schedule with you before we begin, and John keeps the site tidy, safe and moving to plan, updating you as the job progresses. There may be a spell where an upstairs room or the kitchen is out of action, and we plan around that with you so daily life is disrupted as little as possible. Dan and Niko lead the build, from the brickwork and structure to the plastering and finish, and they take real pride in handing back a job done properly.
Double storey extensions almost always need planning permission, because they usually go beyond what permitted development allows, especially on the upper floor and near boundaries. Homes in conservation areas will also need approval, and we will tell you honestly what your project needs and help you through the application. Your extension will also need building regulations approval, covering structure, insulation, drainage and fire safety, and the Party Wall Act often applies because upper-floor work tends to sit close to a neighbour. We guide you through all of it. For more detail, see our planning permission guide.
A simple, predictable process.
You always know what happens next, who's on site, and exactly what it costs.
Free home visit
We come to you, look at your home and boundaries, and talk through what you want on each floor.
Fixed quotation
Marian prepares a clear, itemised quote in writing with no hidden fees.
Design & planning
We prepare drawings and structural calcs, and handle the planning and building-regs approval.
The build
John, Dan and Niko carry out the work, keep the site tidy and stick to the schedule.
Completion
We hand over your finished rooms with their certification and workmanship guarantee.
How much does a double storey extension cost?
As a guide for North London in 2026, a double storey extension costs around £70,000-£130,000. Where you land depends on size, the finishes you choose, the amount of glazing, and structural work such as steel beams and foundations. We give you a fixed, fully itemised written price after a free visit, with no hidden fees.
Guide ranges for North London, 2026 - not fixed quotes. While the headline figure is higher than a single storey build, you get far more space for the money, because you are only paying once for foundations, the roof and scaffolding. For a full breakdown, see our house extension cost page. We put the final figure in writing before any work begins.
What our customers say.
“John and the whole crew were a pleasure to work with. Fast, great communication, finished on time and to a high quality.”
“Dan and Niko put real care into the work; Marian set everything out clearly with no hidden fees. They went above and beyond.”
“We're an architecture practice and have worked with Kev Construct for years. Reliable, trustworthy, excellent finishes.”
Good to know.
Is a double storey extension better value than a single storey one?
In terms of space per pound, often yes. You only pay once for the foundations, roof and scaffolding, yet you gain rooms on two floors, so the cost per square metre usually works out lower. The overall figure is higher because you are adding more space, but for families who need extra bedrooms as well as living space, it is very cost-effective.
Can we stay in the house during a double storey build?
Usually yes, though it depends on the layout. Much of the work happens outside the existing house until we connect the two, so you can often carry on living at home. There may be periods where an upstairs room or the kitchen is out of use. We plan this carefully with you in advance, and John keeps the site safe and clean throughout.
Will a double storey extension match the existing house?
Yes, that is always our aim. We match brickwork, rooflines, windows and detailing as closely as possible so the extension looks like it has always been there, rather than an obvious add-on. Good design and careful building make all the difference. Your architect's drawings guide this, and Dan and Niko take real care to get the finish right.
Do I need a structural engineer?
Yes, a double storey extension needs structural engineer calculations for the beams, foundations and any load-bearing walls being altered. This makes sure the new floors are properly supported and meets building regulations. If you do not already have an engineer, we can point you to trusted people we have worked with, and we build strictly to the approved calculations.
How much value could a double storey extension add?
A double storey extension can add significant value, because it increases both the living space and the number of bedrooms, which is exactly what many North London buyers look for. More importantly, it gives your family the room to grow and enjoy your home now. We build to a high standard so the extension looks right, feels right and lasts.
Ready to add the space
your family needs?
Tell us about your extension and we'll arrange a free home visit. You'll get a clear, fixed price in writing - with no pressure and no hidden fees.
- Free home visit & survey
- Fixed price in writing - no surprises
- Local Edgware team · rated 9.67/10 on Checkatrade
Prefer to talk? 07838 662 225