House Extensions London
Single Storey, Double Storey and Side Return Extensions
You could make more space for a growing family or increase the value of your home with a London home extension. Our extension designs are created with your requirements in mind, and our trained and experienced home extension builders in London will complete them in a matter of weeks.
In London's current financial environment, a house extension is not only a brilliant way to extend your living room, but also a way to get the awesome fresh home feel without the hassle or expense of moving out and buying a new place.
Since, after all, every home is a personal and private space, with each homeowner having different priorities when it comes to the properties of both its interior and exterior, Flint Building Solutions has a degree of experience that you can trust and will accommodate your vision when it comes to building your house extension.
The Professional Extension Builders
Flint Building Solutions design and build extensions all over London and have successfully transformed a countless number of properties to a high level of professionalism.
Using decades of experience constructing property extensions in London, as well as our in-depth knowledge of property markets, planning agencies, problems and solutions, materials, design proposals, technology, and trends, we guide you through your project from start to finish.
So, if your home is in central or the north of London and you have ambitions for a new home or more modest extension dreams, our team will accompany you on your house extension journey from beginning to end.
Want to see finished work? Browse our completed extension projects.
Types of extension we build
Single storey rear extensions, double storey extensions, side return extensions, wraparound extensions, garage conversions, and structural alterations or internal remodelling. Many of our extensions include open-plan kitchen-diners, bi-fold doors, skylights and underfloor heating.
We handle the full build: structural engineering, foundations, steelwork, brickwork, roofing, internal fit-out, plastering, electrics and plumbing. We work alongside architects and structural engineers so the extension meets planning requirements and building regulations, and we manage the programme from first dig to final sign-off.
How much does a house extension cost?
Single storey extensions start from £2,500 per m². A typical 20 m² rear extension therefore starts from around £50,000.
Guide price only. The final figure depends on the ground conditions, access to the rear of the property, the amount of steelwork needed, the glazing you choose and the specification of the kitchen or bathroom inside. We quote every extension individually after a free site visit, with the work broken down so you can see what you are paying for.
How long does it take?
A single storey extension between 15 and 30 m² takes 10 to 16 weeks on site — roughly two and a half to four months from the first dig to a finished, habitable room. Before that, allow time for drawings, structural calculations and Building Control. We give you a realistic programme with your quote, not an optimistic one.
What happens, week by week
Weeks 1–3 — Groundworks and foundations. Excavation, concrete foundations, insulation and the floor slab.
Weeks 4–6 — Structural walls and roof. External walls go up, the roof structure is framed, and the roof is covered in tiles, felt or EPDM.
Weeks 7–8 — Steelwork and breaking through. The RSJ steels go in and the existing external wall comes down to open the house into the new space. This is the noisiest and most disruptive week.
Weeks 9–11 — Wind and watertight. Windows, bi-fold or patio doors and rooflights are fitted. First fix begins: electrical cables and plumbing pipework are run through the walls.
Weeks 12–14 — Plastering and floors. Insulation, plasterboard and plastering. Plaster needs around a week to dry. Floor screeds are laid.
Weeks 15–16 — Second fix and decoration. Sockets, lights, radiators, flooring or tiling, painting and skirting.
House extensions — common questions
Do I need planning permission for an extension? Many single storey rear extensions fall under permitted development, but conservation areas, flats, listed buildings and larger extensions usually need a planning application. We check this before quoting so you know where you stand.
Can I stay in the house during the work? In most cases yes. A rear extension is built from the outside until the final opening-up stage, so the disruption inside is limited to a short period near the end.
Do you deal with Building Control and party wall matters? Yes. We handle Building Control sign-off and advise on party wall notices where a neighbour's wall or boundary is involved.
What areas do you cover? We are based in Waltham Cross and build extensions across north London and Hertfordshire — Enfield, Cheshunt, Barnet, Edmonton, Tottenham, Waltham Abbey and the surrounding areas — as well as central London.