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.
Loft planning permission · London & Hertfordshire
Do you need planning permission for a loft conversion in London? The 2026 rules
By Anderson & the LCCL Construction Team
Finchley N3 · Design & build, LABC award winners 2024 and 2026
Most dormer, L-shaped and hip-to-gable loft conversions in London do not need planning permission — they are permitted development within 40 m³ on a terrace or 50 m³ on a semi or detached house, confirmed by a Lawful Development Certificate. Mansards, front dormers, flats and anything in a conservation area do. This page sets out the volume rules, the conditions that trip people up, what each route costs and how long it takes.
Quick answer
Fees at cost: Lawful Development Certificate £274 (half the householder fee), full application £548 from April 2026. Drawings, submission and approvals are included in the design and build price.
Rear dormer, L-shaped and hip-to-gable within 40 m³ (terrace) or 50 m³ (semi/detached) are usually permitted development; mansards, front dormers, flats and conservation areas need a planning application.
Lawful Development Certificate up to 8 weeks; full application 8 weeks from validation; design before that 4–6 weeks.
A free 30-minute phone call with our team, no obligation.
Without planning
40 m³ terrace · 50 m³ semi/detached
Needs planning
Mansard · front dormer · flats · conservation
Decision
LDC 8 wks · application 8 wks
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 loft conversions are permitted development?
Class B of the permitted development rules, applied to the London roof types. Houses only — flats always need an application.
Conversion
Route
Why
Permitted development
Within 40/50 m³, on the rear slope, set back 20 cm from the eaves, materials to match
Permitted development
Both dormers on rear slopes; the volume is the test — a big outrigger dormer can breach 40 m³ on a terrace
Hip-to-gable + rear dormer
Permitted development
Within 50 m³ on a semi; the gable must not face a highway on a corner plot
Velux / rooflight
Permitted development
Rooflights projecting under 15 cm need no approval at all
Full planning application
Changes the roof profile on the principal elevation; almost always needs permission
Front dormer, roof raise, balcony
Full planning application
Not permitted development — the roof extends beyond the plane facing the road, or the volume is exceeded
Situation
Route
Decision time
House, outside conservation area, within volume
Lawful Development Certificate
Up to 8 wks
House in a conservation area
Full application (roof extensions are excluded from PD there)
8 wks + design
Article 4 area
Full application
8 wks + design
Flat or maisonette
Full application + freeholder consent
8 wks + design
Previous loft or extension already used the volume
Full application
8 wks + design
How the planning stage runs with LCCL
What happens between signing and the scaffold going up.
Stage
What happens
Typical time
1. Address and volume check
Conservation area, Article 4, previous extensions, the volume left in your allowance, head height to the ridge
Day 1
2. Survey and drawings
Measured survey of the roof, then drawings to the standard the council validates first time
2–4 weeks
3. Submission
Lawful Development Certificate or planning application, with a design statement where it helps
Week 4
4. Decision
LDC up to 8 weeks; full application 8 weeks from validation
6–10 weeks
5. Building regulations and party wall
Full-plans drawings, structural calculations, LABC approval; party wall notices 2 months before the steels go in
Runs alongside
6. Scaffold up
Only when everything is signed off — talk to the neighbours before, not after
Week 10–16
The conditions people miss: the volume allowance is measured on the original roof and is used up by any previous extension, including the one the last owner built; the dormer must sit at least 20 cm back from the eaves; no part of the new roof may extend beyond the plane of the existing slope facing a highway; materials must look similar to the house; side-facing windows must be obscure-glazed and fixed below 1.7 m; and no verandas or balconies. Breach one and the project is a planning application. See our planning rules by council for how each borough judges dormers.
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 roof space, stairs and existing structure
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
Lofts 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: talk to next door before the scaffold goes up
Semi-detached hip-to-gable and rear dormer combinations almost always fall under permitted development, but neighbours often object informally — to the council, to the building inspector, to you. Talk to them before the scaffold goes up. We will show them the drawings with you.
It costs nothing, and it is the difference between a quiet twelve weeks and a formal complaint that stalls the job.
“I highly recommend LCCL Construction. They completed our loft conversion to a very high standard, and the quality of workmanship throughout was excellent. The team was professional, reliable, and completed everything within a very reasonable timeframe.…”
Alina A · Google Reviews
“I couldn't be happier with my loft conversion and extension done by LCCL Building Construction. Real craftsmanship, professional management of the entire build from start to finish, seamless integration of new space within the existing one. The work was…”
Plamen Petrov · Trustpilot
“LCCL Construction has beautifully transformed our house with a loft conversion, house extension and renovation including design and build, we are amazed with high quality of the build, professionalism and dedication to successfully complete our highly…”
Leonard Shehu · Google Reviews
Loft planning questions we get asked most
The permitted development volume allowance for roof extensions: 40 cubic metres on a terraced house, 50 on a semi-detached or detached house, measured on the original roof and including any earlier roof extension. A typical rear dormer uses 25–35 m³; an L-shaped dormer on a terrace can use all 40. We measure the volume at the survey before promising a route.
Almost always, because it changes the roof profile on the front of the house and usually exceeds the volume. Mansards are judged on the street's existing mansards — where the neighbours have them the application is usually straightforward; where they do not, expect a longer conversation with the officer.
Yes, but with a planning application: roof extensions are excluded from permitted development in conservation areas. Rear dormers set below the ridge and out of view of the street are usually approved; front dormers and roof raises usually are not.
A Lawful Development Certificate takes up to 8 weeks and a full application 8 weeks from validation, plus 2–4 weeks of survey and drawings before submission. Building regulations and party wall run alongside, so the scaffold goes up 10–16 weeks after signing.
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.
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 lofts 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 lofts: Hampstead NW6, East Barnet EN4, Putney SW15, Wood Green N22, Borehamwood WD6, Hendon NW4 and Marylebone W1.