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Hip to gable loft cost · London & Hertfordshire
Hip to gable loft conversion cost in London 2026: £50,000–£95,000, and what decides it
By Anderson & the LCCL Construction Team
Finchley N3 · Design & build, LABC award winners 2024 and 2026
A hip-to-gable loft conversion in London costs £50,000–£95,000 in 2026, design and build inclusive — the standard answer for a 1930s semi, usually with a rear dormer and usually permitted development. This page gives you the range by configuration, what is in the figure, what moves it, and how to get an itemised estimate for your roof.
Quick answer
£50,000–£95,000 for a hip-to-gable loft conversion, usually with a rear dormer, design and build inclusive. Postcode dependent.
Usually permitted development on a semi within 50 m³; we obtain a Lawful Development Certificate. Conservation and Article 4 areas need a planning application.
10–12 weeks on site; 8–12 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 hip to gable loft conversion cost in London in 2026?
Guide ranges by size, design and build inclusive. Every project is priced from your postcode and house type.
Conversion
Typical use
Guide range
Hip-to-gable only
Gable end rebuilt, Velux windows, one large bedroom
£50,000 – £62,000
Hip-to-gable + rear dormer
Master bedroom with en-suite and a full-height rear wall — the standard semi conversion
£60,000 – £80,000
Double hip-to-gable + dormer (detached)
Both hips rebuilt, two bedrooms and a bathroom
£75,000 – £95,000
Related conversion
Guide range
On site
Rear dormer only
Keeps the hip; smaller room, lower cost
£47,000 – £67,000
8–10 wks
Mansard
New roof across the whole footprint — the most space, usually planning
£64,000 – £124,000
12–16 wks
Loft + rear extension together
The Bohun Grove EN4 combination under one programme
See loft + extension
One programme
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 of the roof, drawings, lawful development certificate or planning, building-regulations drawings, structural calculations
Included in the design and build price; council fees at cost
Structure
New floor joists and steels, dormer or gable structure, roof and windows
The largest share — a dormer adds a box structure, a hip-to-gable rebuilds a roof slope, a mansard replaces the roof
Stairs, fire and insulation
New staircase, fire doors, escape windows, insulation to building regulations
Included; the staircase position is the single biggest design decision
First and second fix
Electrics, plumbing, plaster, decoration
Included
Bathroom or en-suite
Where specified
Included to a sanitaryware allowance; items above the allowance are supplied by you or through us
Party wall
Notices to each adjoining owner where the new steels bear on the shared wall
£300 per notice at cost; surveyor from £750 if a neighbour dissents
Location
Access, parking, conservation conditions
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, drawings, lawful development certificate or planning, building-regulations drawings, structural calculations, new floor structure, dormer or gable structure, roof and windows, stairs, insulation, fire doors and escape windows, first and second fix, plastering, decoration, a bathroom where specified, LABC certificate and guarantees. Not included unless specified: sanitaryware above the allowance, bespoke joinery, party wall surveyor fees if a neighbour dissents (from £750). 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: whether the rear dormer is included (it nearly always should be); the gable wall — blockwork rendered or brick to match the house; the steels, which are longer on a semi because the new floor spans to the new gable; the bathroom; the staircase position; and whether the front slope is re-tiled to match the new gable. 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 roof space, stairs and existing structure
Architectural design and drawings, with revisions until you're happy
Lawful Development Certificate or planning application, 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)
New floor structure, steels, dormer or gable structure, roof and windows
Staircase, insulation, fire doors and escape windows to building regulations
Plaster finish, first-fix electrics and plumbing; bathroom or en-suite where specified
Second-fix carpentry, decoration and the items you supply fitted
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 hip to gable 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: 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.
“We used Lccl construction first time for our kitchen extension 2019 with a view to build a loft conversion afterwards. We just have had our loft conversion completed including bedroom, bathroom, storage loft it has Juliet balcony with velux windows to the…”
Tracie · Trustpilot
“We engaged with LCCL Construction to get our loft conversion and house extension project going. The whole process was explained to us in a straight forward way including how the design stages work, timescales, what to expect during the build and the costs…”
Daniel Freedman · Trustpilot
“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
Cost questions we get asked most
Because a whole roof slope is rebuilt as a vertical gable wall, with longer steels spanning to it, before the dormer goes on. It costs £50,000–£95,000 against £47,000–£67,000 for a rear dormer alone — and it gives the biggest room a semi can have under permitted development.
Nearly always. The hip-to-gable makes the loft wide; the rear dormer makes it tall at the back, which is where the bedroom and en-suite go. Hip-to-gable alone (£50,000–£62,000) suits a house that only needs one large room with Velux windows.
Sanitaryware above the allowance, bespoke joinery, council fees, and party wall surveyor fees if a neighbour dissents (from £750). Survey, design, approvals, structure, stairs, insulation, fire safety, first and second fix, decoration, LABC sign-off and guarantees are in the price.
Usually not on a semi: within 50 m³ it is permitted development and we obtain a Lawful Development Certificate. Conservation areas, Article 4 areas and a gable facing the street on a corner plot need a planning application.
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 lofts: Hampstead NW6, East Barnet EN4, Putney SW15, Wood Green N22, Borehamwood WD6, Hendon NW4 and Marylebone W1.