Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
Services
Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
Services
Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
Services
Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
Services
Call 020 8037 7332 or get an instant estimate online.
Side return extensions · London & Hertfordshire
Side return extension London: cost, planning rules and build time — from £42,000 inc. VAT (£35,000 + VAT)
By Anderson & the LCCL Construction Team
Finchley N3 · Design & build, LABC award winners 2024 and 2026
The side return is the narrow strip beside the outrigger of a Victorian or Edwardian terrace — usually 1.5 to 2.5 m wide and doing nothing. Filling it turns a galley kitchen into a full-width kitchen-diner without losing garden depth. This page gives you the 2026 numbers, the permitted development rules that apply to terraces, the outrigger and roof options, and how the job runs with one team.
Quick answer
£35,000–£78,000 for a single-storey side return extension, design and build inclusive (kitchen on top). Postcode dependent.
Usually none: a side extension up to half the width of the original house and single-storey is permitted development. Lawful Development Certificate included.
10–14 weeks on site; 8–16 weeks of design and approvals before that.
A free 30-minute phone call with our team, no obligation.
Guide price
£42,000 – £93,600 inc. VAT (£35,000 – £78,000 + VAT)
Typical build
10–14 weeks on site
Guarantee
12-month workmanship guarantee; 10-year LABC structural warranty
Awards
LABC 2024 & 2026 winners
LABC Building Excellence Award 2024
Best Residential Extension in London — Bohun Grove, East Barnet EN4: rear extension, hip-to-gable loft conversion and whole-house renovation
LABC Building Excellence Awards 2026
London Regional Winner, Best Conversion or Alteration — Weech Road, Hampstead NW6: penthouse loft conversion and full renovation
One contract
Architecture, structural engineering, planning, construction and project management — all under one contract
Guaranteed & insured
12-month workmanship guarantee; 10-year LABC structural warranty
What a side return extension from LCCL includes
Design and build inclusive — the price covers the whole job, not just the bricks.
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; 10-year LABC structural warranty
How much does a side return extension cost in London in 2026?
Guide ranges, design and build inclusive. Every project is priced from your postcode and house type.
Side return
Typical use
Guide range
Infill only (≈8–12 m²)
Galley kitchen widened to full width, glazed roof
£42,000 – £60,000 inc. VAT (£35,000 – £50,000 + VAT)
Infill + knock-through (≈12–18 m²)
Kitchen and dining opened into one room, steel across the outrigger wall
£57,600 – £78,000 inc. VAT (£48,000 – £65,000 + VAT)
Infill + rear step-out (≈18–25 m²)
Side return plus 1–2 m beyond the outrigger — an L-shaped rear
£72,000 – £93,600 inc. VAT (£60,000 – £78,000 + VAT)
Related extension
Guide range
On site
Rear extension
Depth rather than width — 3–6 m beyond the back wall
£42,000 – £90,000 inc. VAT (£35,000 – £75,000 + VAT)
10–14 wks
Wraparound extension
Side return and rear together, one scaffold, one contract
£72,000 – £153,600 inc. VAT (£60,000 – £128,000 + VAT)
14–18 wks
What the price includes: survey, architectural drawings, lawful development certificate or planning, building-regulations drawings, structural calculations, construction to plaster finish with first-fix electrics and plumbing, LABC sign-off and guarantees. On top: the kitchen itself, supplied and fitted (£9,000 – £87,360 inc. VAT (£7,500 – £72,800 + VAT) by size and specification; appliances extra), 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 length of the side return and whether you step out beyond the outrigger; the roof — a fully glazed roof or a run of rooflights against a flat roof with a lantern; how much of the outrigger wall comes out and the steel that replaces it (on a Victorian terrace typically £4,800 – £19,200 inc. VAT (£4,000 – £16,000 + VAT)); drainage running under the new floor and whether a Thames Water build-over agreement is needed; and the finish level inside.
Side return extensions by house type
Victorian terrace with outrigger
The classic case. The side return is filled from the front of the outrigger to the back wall, the outrigger wall comes out onto a steel, and the kitchen runs full width. Permitted development if the extension is single-storey, no wider than half the original house and no higher than 4 m; a Lawful Development Certificate proves it. Both neighbours usually get party wall notices.
Edwardian semi with side passage
Wider side returns (2–3 m) and often a side door to the garden. The question is whether to keep a side access: many clients keep a 1 m passage and fill the rest. Permitted development limits are the same; a boundary wall built up to 3 m at the eaves is allowed within 2 m of the boundary.
Terrace in a conservation area
Side extensions are often restricted by Article 4 directions — Islington, Camden and parts of Haringey and Hackney in particular. A planning application is needed and the roof form matters to the officer. We check the address before the first drawing.
Planning
Do you need planning permission for a side return extension?
Usually not on a house. The permitted development limits for side extensions are about width and height, not depth.
Route
Limits
Time
What we do
1. Permitted development
Single-storey, no wider than half the original house, max 4 m high (3 m eaves within 2 m of a boundary)
No application
Lawful Development Certificate, ~8 weeks, included
2. Full planning
Conservation areas, Article 4 areas, flats, side + rear beyond PD limits
8 weeks
Drawings, design statement and application by our team
3. Prior approval
Only where the extension also goes beyond 3 m to the rear
42 days
Larger home extension submission with neighbour notification
Building regulations & party walls
The other two approvals
Every extension needs building-regulations approval whether or not it needs planning: foundations, structure, insulation, glazing area, drainage and fire. We do this through LABC with full-plans drawings and our own structural calculations, so the inspector is checking a design he has already approved, not improvising on site.
If the extension is on or near the boundary of a semi or terrace, the Party Wall Act applies. Notices go out at least two months before we start; most neighbours consent, and where a surveyor is appointed we manage it.
Side extensions cannot use the larger home extension (prior approval) route on their own — that scheme is for depth, not width. Where a side return is combined with a rear step-out beyond 3 m, the rear part goes through prior approval and the side part must still meet the permitted development limits, or the whole thing goes to full planning as a wraparound.
Permitted development rights for house extensions · Side return extension cost guide See our permitted development projects page for every loft and extension you can build without a planning application, with from-prices at economy specification.
Recent side return extension 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
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ANDERSON · FOUNDER, LCCL CONSTRUCTION
Anderson's advice: budget for the steelwork, not just the kitchen
Clients budget for kitchen units but forget the structural steelwork when opening up ground-floor walls. On a Victorian terrace that is typically £4,800 – £19,200 inc. VAT (£4,000 – £16,000 + VAT) for the load-bearing opening, depending on its width — we price it on every proposal so there is no surprise.
Get the structural design done early, from a measured survey, and the steel arrives on site the week it is needed rather than holding the programme.
How a side return extension runs with LCCL
From the first call to the completion certificate. Design, planning and building regulations typically take 8–16 weeks before work starts; party wall agreements on a terrace can add up to three months if left late.
WEEK 0
Free consultation call
A 30-minute phone call with our team about the house, what you want from the space and a realistic budget. Your instant estimate is the starting point.
WEEKS 1–4
Survey & design
Measured survey, architectural drawings and your detailed itemised estimate — design, planning, structure, construction and warranty priced line by line.
WEEKS 4–12
Approvals
Lawful Development Certificate or planning application, building-regulations drawings, structural calculations, party wall notices. Nothing starts on site until it is signed off.
BUILD
On site
10–14 weeks on site for a single-storey side return extension. Weekly updates from your project manager, one point of contact throughout.
HANDOVER
Sign-off
Snagging, LABC final inspection and completion certificate, guarantees in writing. 10-year LABC structural warranty.
“We are very happy with the services from Lccl, Alex has done a great job on design and construction. We have used Lccl in the past for our rear house extension and have come back to instruct Lccl for our loft conversion too to our house in North London.”
Mia M · Google Reviews
“The Lccl construction team built my extension with a quick and clean service, they worked non stop through the winter weather.. I would highly recommend this company!”
Chris Dunn · Google Reviews
“LCCL Construction was the right company to help with my loft conversion. I heard of other people's challenging experiences with building works so I was very careful which company I chose. LCCL Constructions was professional, trustworthy and worked to the…”
KashImaging · Trustpilot
Side return extension questions we get asked most
£42,000 – £93,600 inc. VAT (£35,000 – £78,000 + VAT) in 2026, design and build inclusive — survey, drawings, lawful development certificate, structural calculations, construction to plaster finish and building-control sign-off. A straightforward infill with a glazed roof sits at the bottom of the range; an infill with a rear step-out and a full knock-through at the top. The kitchen itself is on top.
On most houses, no. A single-storey side extension no wider than half the original house and no higher than 4 m is permitted development, and we obtain a Lawful Development Certificate so it is documented when you sell. Flats, conservation areas and Article 4 areas are the exceptions and need a planning application.
Between 1.5 m and 2.5 m on most Victorian and Edwardian terraces — enough to turn a 2.5 m galley into a 4–5 m wide kitchen-diner. Below about 1.2 m the space rarely justifies the cost of the steel and the roof; above 3 m it is usually treated as a side extension in its own right.
Ten to fourteen weeks on site, plus 8–16 weeks before that for design and approvals. If you add a rear step-out the build runs closer to the wraparound programme of 14–18 weeks.
A fully glazed roof gives the most light and the most heat in summer; a flat roof with two or three large rooflights is lower-cost, easier to insulate and easier to keep clean. Most of our clients choose the rooflights and spend the difference on the doors. We draw both so you can decide from the plan.
Only if you choose to. Many clients keep a 1 m passage to the garden and fill the rest of the side return, or fit a door in the new side wall. It is a design decision we settle on the survey visit.
Almost always on a terrace — the new wall sits on or against the boundary and the steel bears on the party wall. We serve the notices for you at cost (£300 each) at design stage so the two-month notice period runs alongside the approvals, and most neighbours consent without appointing a surveyor.
A side return gives width in the existing kitchen for the least money and usually no planning application; a rear extension gives depth and a proper dining space. If the budget stretches, a wraparound does both under one contract and one scaffold. The free consultation call is the quickest way to settle it for your house.
Where we build side return extensions
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 side return extensions: East Finchley N2 and Queen's Park W10.