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Wraparound extension cost · London & Hertfordshire
Wraparound extension cost in London 2026: £60,000–£128,000, and where the money goes
By Anderson & the LCCL Construction Team
Finchley N3 · Design & build, LABC award winners 2024 and 2026
A wraparound extension — side return and rear together — costs £60,000–£128,000 in London in 2026, design and build inclusive. It is the largest single-storey change you can make to a terrace or semi and it usually needs a planning application. This page gives you the range by footprint, what is in the figure, what moves it, and how to get an itemised estimate.
Quick answer
£60,000–£128,000 for a single-storey wraparound extension, design and build inclusive (kitchen on top). Postcode dependent.
Usually a planning application: the combined side and rear extension exceeds permitted development on most houses. We prepare and submit it; pre-application advice where the borough is helpful.
14–20 weeks on site; 10–16 weeks of design and approvals before that.
A free 30-minute phone call with our team, no obligation.
LABC Building Excellence Award 2024
Best Residential Extension in London — Bohun Grove, East Barnet EN4
LABC Building Excellence Awards 2026
London Regional Winner, Best Conversion or Alteration — Weech Road NW6
One contract
Architecture, structural engineering, planning, construction and project management — all under one contract
Guaranteed & insured
12-month workmanship guarantee, structural guarantee to building-control sign-off, 10-year LABC Warranty available
How much does a wraparound extension cost in London in 2026?
Guide ranges by size, design and build inclusive. Every project is priced from your postcode and house type.
Size (footprint)
Typical use
Guide range
Side return + 3 m rear (≈25–30 m²)
Full-width kitchen-diner, garden doors across the back
£60,000 – £85,000
Side return + 4–5 m rear (≈30–40 m²)
Kitchen, dining and a seating area, utility off the side
£80,000 – £110,000
Side return + 6 m rear (≈40–50 m²)
Open-plan kitchen, dining, living and utility, large glazing spans
£105,000 – £128,000
Related extension
Guide range
On site
Side return only
Width without the rear step-out
£35,000 – £78,000
10–14 wks
Rear extension only
Depth without the side return
£35,000 – £75,000
10–14 wks
Double-storey wraparound
Wraparound below, bedrooms above — always a planning application
£130,000 – £260,000
22–30 wks
Where the money goes
What a design and build price is made of, and which lines are priced separately.
Cost element
What it covers
How it is priced
Survey, design and approvals
Measured survey, architectural drawings, planning or lawful development certificate, building-regulations drawings, structural calculations
Included in the design and build price; council application fees at cost
Structural steelwork
Steels, padstones and the engineer's design where the back or outrigger walls come out
Typically £4,000–£12,000 on a Victorian terrace — in every estimate from day one
Shell
Foundations, drainage, walls, roof, rooflights, doors and windows to weather-tight
The largest share — priced from the survey and the drawings, not per m²
First and second fix
Electrics, plumbing, underfloor heating where specified, plaster, decoration, flooring fitted
Included; the items you choose (tiles, flooring, sanitaryware) are supplied by you or through us
Kitchen fit-out
Units, worktops, appliances
£15,000–£30,000 mid-range, £30,000–£75,000 high specification — priced separately from the build
Party wall
Notices to each adjoining owner; surveyor only if a neighbour dissents
£300 per notice at cost; surveyor from £750 per neighbour
Location
Access, parking, conservation conditions, logistics
Inner London +10–15%, Central London +20–25%, Hertfordshire about 5% less
Added afterwards
—
Nothing: the figure on your itemised estimate is the figure you pay
What the price includes: survey, architectural drawings, planning or lawful development certificate, building-regulations drawings, structural calculations, construction to plaster finish with first-fix electrics and plumbing, LABC sign-off and guarantees. On top: kitchen units, worktops and appliances (typically £15,000–£75,000), flooring and second-fix items you choose. The figure on your itemised estimate is the figure you pay — nothing is added afterwards. Postcode dependent — the instant estimator adjusts the range for your area in thirty seconds, and a detailed itemised estimate follows one survey.
What moves the price: the rear depth more than the side width; the length of the steel across the corner where the two wings meet (the single largest structural item); glazing — corner-less sliding doors and a run of rooflights are the biggest variable; a flat roof with lanterns versus a pitched or part-glazed roof; drainage rerouted around the new footprint; and the finish inside. Inner London (Camden, Islington, Hackney, Wandsworth, Hammersmith and similar) add 10–15%. Central London (Westminster, Kensington & Chelsea, the City) add 20–25%. Hertfordshire is about 5% less. These are estimated ranges — every home is surveyed and costed individually.
What the price includes
Design and build inclusive — one contract from the first sketch to the completion certificate.
Measured survey of the house and garden
Architectural design and drawings, with revisions until you're happy
Planning application or Lawful Development Certificate, prepared and submitted for you
Building regulations drawings and structural calculations by our chartered engineer
Party wall notices served on your behalf (£300 each, at cost)
Foundations, drainage and any build-over agreement with Thames Water
Structure, roof, rooflights, doors and windows to a weather-tight shell
Plaster finish, first-fix electrics and plumbing, underfloor heating where specified
Fitting of the kitchen, flooring and second-fix items you supply
LABC inspections and completion certificate
A dedicated project manager and a weekly progress update
12-month workmanship guarantee and structural guarantee; 10-year LABC Warranty available
Recent wraparound projects
Bohun Grove, East Barnet EN4 — rear extension, hip-to-gable loft and whole-house renovation
LABC 2024 Best Residential Extension in London
Semi-detached family home One programme loft + extension + renovation
A total renovation of a family semi: a rear extension opening into a full-width kitchen and dining space with floor-to-ceiling glazing and skylights, a hip-to-gable loft conversion with a rear dormer, two Lusso Stone bathrooms, enlarged bedrooms, new windows throughout, a regulated outbuilding and landscaping.
Because the loft and extension ran under one contract, the steelwork for the open-plan ground floor and the loft floor was designed together and lifted in on the same day — one crane hire, one scaffold, one building-control file.
See the Bohun Grove project · All projects
ANDERSON · FOUNDER, LCCL CONSTRUCTION
Anderson's advice: use pre-application advice where the council is helpful
Wandsworth planning is much more helpful on pre-application advice than Islington in our experience. Where a borough engages, a pre-app meeting before the full application saves a refusal and a resubmission; where it does not, a well-argued design statement and precedent search do more.
We know which boroughs are which because we apply in them every month — and we tell you before you pay a pre-app fee whether it is worth it for your address.
“We are very pleased to have used Lccl Construction to do full house renovation and loft conversion to our edwardian terraced house. Project involved total strip out of interiors and remodelling repositioning the interior walls, electrical and plumbing…”
neil smith · Trustpilot
“We did a 3x10m single storey rear extension with LCCL recently. It was scheduled to take 12 weeks to complete but with Alex's experience and agile project management, we are ahead of schedule (finished in 10). Alex, and LCCL,is extremely knowledgeable and…”
Galichet Christophe · Google Reviews
“Hired LCCL Construction to design and build us a rear house extension. Found them easy to work with and are pleased with the results. They have been recommended to us for the whole build including designs and construction. The rear extension feels amazing,…”
James Grimsdale · Google Reviews
Cost questions we get asked most
If you want width and depth, yes: £60,000–£128,000 against £35,000–£75,000 buys an L-shaped open-plan ground floor rather than a deeper room, and the scaffold, design and party wall process are shared. If you only need depth, a rear extension is the better spend.
Almost always, because the combined side and rear footprint exceeds permitted development. We prepare the application and use pre-application advice where the borough engages — Wandsworth is far more helpful than Islington in our experience.
The steel across the corner where the side and rear wings meet, and the glazing. Corner-less sliding doors and a run of rooflights can move the price by tens of thousands on the same footprint.
Kitchen units, worktops and appliances (typically £15,000–£75,000), flooring and second-fix items you choose, bespoke joinery, landscaping, council fees, and party wall surveyor fees if a neighbour dissents (from £750). Survey, design, planning, structure, build, LABC sign-off and guarantees are in the price.
Yes. Inner London (Camden, Islington, Hackney, Wandsworth, Hammersmith and similar) adds 10–15%, Central London (Westminster, Kensington & Chelsea, the City) adds 20–25% and Hertfordshire is about 5% less — the difference is parking, access, conservation-area conditions, party wall complexity and logistics. The instant estimator applies the right band to your postcode.
No. The figure on your itemised estimate is the figure you pay — nothing is added afterwards. Items you choose, such as kitchen units or sanitaryware above the allowance, are listed separately before you sign.
Two steps. The instant estimator gives you a range for your postcode and project in thirty seconds. Then one measured survey gives you a detailed itemised estimate — design, planning, structure, construction and warranty priced line by line — with no obligation.
A 12-month workmanship guarantee and a structural guarantee on every project, with a 10-year LABC Warranty available. Building control sign-off is through LABC — we are an LABC Registered Partner and LABC Building Excellence Award winners in 2024 and 2026.
Where we build
From Finchley N3 we cover North London, North-West London, Central London, South-West and West London, and Hertfordshire — and we also work across the rest of London, Buckinghamshire, Surrey, Kent and Essex. Recent extensions: East Barnet EN4, Finchley N3, Putney SW15, Mill Hill NW7, Wood Green N22 and Borehamwood WD6.