Loft conversions, house extensions, renovations, basements and new builds across London and Hertfordshire.
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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
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Extension planning permission · London & Hertfordshire
Do you need planning permission for a house extension in London? The 2026 rules
By Anderson & the LCCL Construction Team
Finchley N3 · Design & build, LABC award winners 2024 and 2026
Most single-storey rear and side return extensions in London do not need planning permission — they are permitted development, confirmed by a Lawful Development Certificate. Wraparounds, two-storey extensions, flats and anything in a conservation or Article 4 area do. This page sets out the limits, the three routes, what each costs and how long it takes, and what changes the answer for your address.
Quick answer
Fees at cost: householder application £548 from April 2026, Lawful Development Certificate half that, prior approval £249. Our design, drawings and submission are included in the design and build price.
Single-storey rear to 3 m (4 m detached) and side returns are usually permitted development; 6 m (8 m) by prior approval; wraparounds, two storeys, flats and Article 4 areas need a full application.
Lawful Development Certificate up to 8 weeks; prior approval 42 days; full application 8 weeks from validation, longer if the officer asks for changes.
A free 30-minute phone call with our team, no obligation.
Without planning
3 m / 4 m rear, side to half width
Prior approval
6 m / 8 m rear, 42 days
Full application
8 weeks, £548
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
Which route does your extension take?
The three routes to a lawful extension in England, and what decides between them. Rules for houses outside conservation areas; flats and Article 4 areas always need a full application.
Route
Applies to
Council fee
Permitted development + Lawful Development Certificate
Single-storey rear to 3 m (terrace/semi) or 4 m (detached), max 4 m high; side return up to half the original width; total footprint under half the garden; materials to match
Half the householder fee — £274
Prior approval (larger home extension)
Single-storey rear 3–6 m (terrace/semi) or 4–8 m (detached); council notifies neighbours, 42-day decision
£249
Full planning application
Wraparounds, two-storey and first-floor extensions, anything in a conservation or Article 4 area, flats, listed buildings, extensions beyond the limits
£548 from April 2026
Extension type
Usual route
Decision time
Rear extension 3 m
Permitted development
LDC up to 8 wks
Rear extension 4–6 m
Prior approval
42 days
Side return infill
Permitted development
LDC up to 8 wks
Wraparound
Full application
8 wks + design
Two storey / first floor over outrigger
Full application
8 wks + design
Any extension to a flat
Full application + freeholder consent
8 wks + design
How the planning stage runs with LCCL
What happens between signing and the first day on site — nothing starts until every approval is in.
Stage
What happens
Typical time
1. Address check
Conservation area, Article 4, listed status, flats, what the previous owner built — we tell you the route before you pay for a drawing
Day 1
2. Survey and drawings
Measured survey, then drawings to the standard the council validates first time
2–4 weeks
3. Pre-application advice
Only where the borough engages — Wandsworth yes, Islington rarely; we tell you if it is worth the fee
4–6 weeks where used
4. Submission
LDC, prior approval or full application, with design statement and precedent search where they help
Week 4–5
5. Decision
LDC up to 8 weeks; prior approval 42 days; full application 8 weeks from validation
6–12 weeks
6. Building regulations and party wall
Full-plans drawings, structural calculations, LABC approval; party wall notices 2 months before we start
Runs alongside
7. Start on site
Only when planning, building control and party wall are all signed off
Week 12–20
What the limits mean in practice: permitted development is a set of national rules — the 3 m / 4 m depth, the 4 m height, the half-width side rule, the half-garden footprint, matching materials — that let you extend without asking the council. Inside a conservation area a single-storey rear extension within those limits is still permitted development unless an Article 4 direction removes it; side, roof and two-storey extensions there need permission. Each council then sits its own design guide on top for anything that needs an application — see our planning rules by council page for the 27 boroughs we work in.
Fees at cost: a householder planning application is £548 from 1 April 2026 plus the Planning Portal service charge; a Lawful Development Certificate for proposed works is half that; larger home extension prior approval is £249. Building-control charges are set by each council. Party wall notices £300 each; a surveyor only if a neighbour dissents (from £750 per neighbour). The figure on your itemised estimate is the figure you pay — nothing is added afterwards.
What LCCL does for you at the planning stage
Design and build inclusive — the drawings, the application and the approvals are in the price.
Address check before the first drawing — conservation area, Article 4, listed status, flats, previous extensions
Measured survey of the house and garden
Architectural drawings to the standard the council validates first time
Lawful Development Certificate or planning application, prepared and submitted for you
Pre-application advice where the borough is helpful (we tell you if it is worth the fee)
Design and access statement, precedent search and neighbour drawings where they help
Building-regulations drawings and structural calculations by our chartered engineer
Party wall notices served on your behalf (£300 each, at cost)
LABC full-plans approval, inspections and completion certificate
One project manager for the paperwork and the build — nothing starts on site until it is signed off
12-month workmanship guarantee; 10-year LABC structural warranty
Extensions we took through planning
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: 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 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
Extension planning questions we get asked most
On a house outside a conservation or Article 4 area: a single-storey rear extension to 3 m (terrace or semi) or 4 m (detached), no higher than 4 m; a side extension up to half the width of the original house; and the total footprint of all extensions under half the garden. Go to 6 m / 8 m through prior approval. Two storeys, wraparounds and anything on a flat need a full application.
The larger home extension scheme: a single-storey rear extension up to 6 m on a terrace or semi, 8 m on a detached house, through prior approval rather than a full application. You notify the council, it writes to the adjoining neighbours, and unless one objects within 21 days the extension is approved by default after 42 days. Fee £249.
A Lawful Development Certificate takes up to 8 weeks, prior approval 42 days, and a full householder application 8 weeks from the date the council validates it — plus the design time before submission. Budget 8–16 weeks from survey to a decision, and start the design in summer if you want to be on site in the autumn.
A certificate from the council confirming that your extension or loft is permitted development and does not need planning permission. It is optional in law but we obtain one on every permitted-development project: it costs half the householder fee, takes up to 8 weeks, and it is the document your buyer's solicitor will ask for when you sell.
A council order that removes permitted development rights in a defined area, usually a conservation area. In an Article 4 area even a small rear extension or a rear dormer needs a planning application. We check the council's Article 4 schedule for your address before the first drawing — it changes the route, the fee and the timescale.
Not if it is permitted development within the limits — there is no consultation. On a prior-approval (6 m / 8 m) extension the council notifies the adjoining neighbours and only an objection triggers an assessment. On a full planning application neighbours can comment and the officer weighs daylight, outlook and privacy. Talk to them first; we will show them the drawings with you.
No. Flats and maisonettes have no permitted development rights for extensions or lofts, so every project is a planning application — and usually the freeholder's consent as well. We handle both.
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.
Where we take extensions through planning
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.