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House Extensions in London
Rear, side return, wrap-around and double-storey extensions.
House Extensions in London
Most London houses do not need more rooms. They need the ground floor to stop being three dark boxes.
An extension is rarely about floor area on its own. The projects that transform a house are the ones that fix circulation and light at the same time — opening the back of the plan, pulling the kitchen into the garden, and making the room you actually live in the best room in the property rather than the one at the end of a corridor.
We build rear extensions, side return infills, wrap-arounds and full two-storey additions across Greater London. Because the structural work, the carpentry, the first fix and the finishing are all ours, the sequence holds together — which is what stops an extension turning into the eight-month job that everyone on your street warns you about.
What you get
How we approach it
Groundworks done properly
Trial holes, foundation depth set against the actual ground and any nearby trees, and drainage diverted and rodded — the part nobody sees and the part that causes every expensive problem.
Structural openings
Steel goal-post frames, padstones and temporary propping to open the back of the house up fully, designed with your engineer and installed to their calculations.
Glazing that performs
Sliding, bifold or fixed glazing set out early so the structural opening is built to the manufacturer tolerance rather than packed out on the day it arrives.
Thermal detail
Insulation lines that actually meet at the junctions, taped airtightness and a warm roof build-up — so the new room is not the cold one in February.
Options
Extension types we build
The right form depends on your plot, your neighbours and what the plan is failing to do today.
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01Rear extension
Most flexibleStraight out into the garden. Under permitted development a terrace or semi can usually go 3m, a detached 4m, with the larger home extension scheme doubling both subject to a prior approval application and neighbour consultation.
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02Side return infill
Victorian terracesThe narrow alley beside the back addition of a Victorian terrace, roofed and brought inside. It adds relatively little area but transforms a dark galley kitchen into a full-width room — the highest impact per pound in London.
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03Wrap-around
Largest ground floorRear and side return combined into one L-shaped space. The most ambitious ground-floor move, and the one that lets you place the kitchen, dining and living zones properly rather than fitting them around what was already there.
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04Double-storey extension
Adds bedroomsExtra bedroom and bathroom above a new ground-floor room. More foundation, more structure and usually a planning application, but the cheapest way to add a bedroom where the loft is already converted or unusable.
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05Garage conversion and infill
Lowest costAn attached garage is often the simplest extension on the plot — the walls and roof exist. Floor level, damp, insulation and a new opening are the work; the shell is already paid for.
Before you start
What determines whether it is straightforward
The items below are where projects most often stall. We raise them at survey stage, not halfway through.
Permitted development vs planning
Height, depth, eaves line, materials and how much of the garden is left all decide it. We will tell you at survey which route your project is on and what the prior approval timeline adds.
Party wall awards
Excavating within 3m of a neighbouring structure, or building on the line of junction, triggers notices. Budget two months and a surveyor fee — and serve early.
Drainage and build-over
Building over or near a public sewer needs a build-over agreement with Thames Water. This is routinely the thing that delays a start on site, so we identify it at survey.
Trees and foundations
A mature tree near the extension changes foundation depth dramatically on London clay. Better to find that in a trial hole than in a variation halfway through.
Where we work
House Extensions across London
We deliver this service across all 33 London boroughs. Pick your area for local planning context, typical property types and recent work nearby.
Coverage mapFAQs
House Extensions — your questions answered
The questions we are asked most often about this service. If yours is not here, call us — we would rather answer it now than after you have committed.
As a planning figure, a good-quality single-storey rear extension in London generally lands somewhere in the region of £2,200 to £3,200 per square metre before VAT, kitchens and glazing, with side returns at the higher end because of the structural work involved. The only number worth acting on is one written after a survey of your property.
A single-storey rear extension is typically twelve to sixteen weeks on site once foundations start. A wrap-around or two-storey runs twenty to thirty. The design, planning and party wall stage in front of it is commonly three to six months.
Usually not for all of it. Where the layout allows we keep the existing kitchen running until the new shell is watertight, then do the changeover in a defined window. We will tell you honestly at survey how many weeks you should plan to be on a temporary kitchen.
For anything involving a new opening or a new roof, yes to both. We work alongside yours, or can introduce you to practices we have built with before. We do not mark up their fees.
It is priced, written down and agreed with you before it is done. Asbestos in an old kitchen ceiling, an unrecorded drain run or shallow foundations are the common ones, and they are the reason we open trial holes before quoting rather than after.
Free quotation
Thinking about house extensions?
Let us take a look.
Tell us what you are planning and we will arrange a free site survey and a written, itemised quotation — with no obligation and no sales visit.