Loft Conversion Company North London — Fixed-Price Lofts and Extensions, Finchley N3 Based

LCCL Construction is a loft conversion and extension company based in Finchley N3, working across North London for over 20 years. One team, one contract: architects, structural engineers, project managers and builders coordinated by LCCL take your loft from first sketch to handover — or, if you already have an architect's drawings, engineer's calculations and party wall awards, we price and build from them as drawn.

North London is home ground: our office is in Finchley N3 and most of our team lives in these postcodes. The 1930s semis of Barnet, Finchley, Hendon and Edgware have hipped roofs that suit hip-to-gable conversions; the Edwardian terraces of Crouch End and Muswell Hill take L-shaped dormers, side-return and rear extensions well; Highgate, Hampstead and Islington bring conservation-area sensitivity; the post-war homes across Enfield and Barnet give the best value per pound.

Fixed-price permitted development lofts in North London

Most North London lofts outside a conservation area need no planning application. We price the common ones as fixed-price permitted development projects at economy specification, design and build inclusive, with the Lawful Development Certificate and building regulations included. Inc. VAT, ex-VAT in brackets, postcode dependent:

• Velux / rooflight loft: from £32,400 inc. VAT (£27,000 + VAT)
• Rear dormer loft: from £56,400 inc. VAT (£47,000 + VAT)
• L-shaped dormer (Victorian and Edwardian terraces): from £58,800 inc. VAT (£49,000 + VAT)
• Hip to gable (1930s semis): from £60,000 inc. VAT (£50,000 + VAT)
• Loft and rear extension together: from £98,400 inc. VAT (£82,000 + VAT) — two allowances, one scaffold, one contract

A mansard needs planning permission and is priced from £76,800 inc. VAT (£64,000 + VAT). See every permitted development project with its from-price and the five checks we run before we confirm a loft qualifies.

Five checks before you appoint a loft conversion company in North London

"Loft conversion company" covers builders, build managers and lead-generation directories. Five questions separate them:

1. Who do you sign with? One contract with the company that designs, engineers and builds — not a design fee here and a builder's contract there. At LCCL the contract, the structural design and the build are ours.
2. Is the price fixed? Ask for an itemised written estimate, inc. VAT with the ex-VAT figure shown, for the scope on the drawings — and ask what is excluded. Our economy-specification from-prices above are the starting point; your written estimate is fixed once the Schedule of Works is agreed.
3. Who signs off the structure? Full-plans building regulations through LABC, with inspections at each stage and a completion certificate at the end. LCCL is an LABC Registered Partner and a National Federation of Builders member.
4. What is guaranteed? A 12-month workmanship guarantee and a 10-year LABC structural warranty, in writing, on every project.
5. Can you see the work? Reviews on Google, Trustpilot and Reviews.io, and finished projects you can read about by street: Weech Road NW6 and Bohun Grove EN4 are both LABC award winners.

What it costs across North London

The final figure depends on postcode, access and site conditions — the instant estimate applies your area. Guide ranges for 2026, design and build inclusive (architecture, structural engineering, planning or LDC, construction, project management and building control). Every project is surveyed and priced individually.

• Velux loft: £32,400 – £50,400 inc. VAT (£27,000 – £42,000 + VAT)
• Rear dormer loft: £56,400 – £80,400 inc. VAT (£47,000 – £67,000 + VAT)
• L-shaped dormer: £58,800 – £98,400 inc. VAT (£49,000 – £82,000 + VAT)
• Hip to gable: £60,000 – £114,000 inc. VAT (£50,000 – £95,000 + VAT)
• Mansard: £76,800 – £148,800 inc. VAT (£64,000 – £124,000 + VAT)
• Rear extension: £42,000 – £90,000 inc. VAT (£35,000 – £75,000 + VAT)
• Side return: £42,000 – £93,600 inc. VAT (£35,000 – £78,000 + VAT)
• Garage conversion: £21,600 – £36,000 inc. VAT (£18,000 – £30,000 + VAT)
• Wraparound: £72,000 – £153,600 inc. VAT (£60,000 – £128,000 + VAT)
• Double storey: £90,000 – £198,000 inc. VAT (£75,000 – £165,000 + VAT)

Kitchen on top of the structure, supplied and fitted: +£9,000 – £87,360 inc. VAT (£7,500 – £72,800 + VAT) depending on size and specification. Basements: cellar refit £54,000 – £114,000 inc. VAT (£45,000 – £95,000 + VAT), lowering £114,000 – £216,000 inc. VAT (£95,000 – £180,000 + VAT), new dig £216,000 – £360,000 inc. VAT (£180,000 – £300,000 + VAT)+. New build: £2,200 – £4,500 per sqm (zero-rated for VAT).

Recent LCCL loft projects in North London

Weech Road NW6 — loft conversion and top-floor alteration, LABC London Regional Winner 2026

A renovation, loft conversion and alteration of the top floor into a penthouse-style storey — LABC Building Excellence Awards 2026 London Regional Winner, Best Conversion or Alteration to an Existing Home, nominated by the inspector who signed it off.

See the project

Bohun Grove, East Barnet EN4 — hip-to-gable loft, rear extension and whole-house renovation

A total renovation: hip-to-gable loft conversion, rear extension with an open-plan kitchen, two Lusso Stone bathrooms, enlarged bedrooms, new windows, skylights and floor-to-ceiling glazing, a regulated outbuilding and landscaping. LABC Building Excellence Award 2024, Best Residential Extension in London.

See the project

Planning across North London

Six planning authorities with different appetites. Barnet and Enfield are generally straightforward for permitted-development lofts and single-storey rear extensions; Haringey, Camden and Islington have extensive conservation areas where rear dormers and roof extensions need planning permission and careful detailing. We apply for a Lawful Development Certificate on every permitted-development project so the position is confirmed in writing.

Barnet: conservation areas, Article 4 and the new SPD

Barnet — the borough we are based in — has 16 conservation areas, ten of them with Article 4 directions removing some permitted development rights: Monken Hadley, Totteridge, Wood Street, Mill Hill, Finchley Church End, Finchley Garden Village, Glenhill Close, Moss Hall Crescent, Hendon The Burroughs and Hampstead Garden Suburb (where any extension or external change needs planning permission and Trust approval). A borough-wide Article 4 direction has required planning permission for small HMO conversions since May 2016. The Local Plan 2021–2036 was adopted in March 2025, and the Sustainable Design and Development Guidance SPD adopted on 15 June 2026 (replacing the 2016 Residential Design Guidance) sets the rear-extension depths (3 m terrace, 3.5 m semi, 4 m detached), two-storey and side-extension limits, dormer set-backs and basement rules. Householder applications cost £548 from April 2026 with an eight-week decision period. See our Barnet, Finchley, Hendon, Mill Hill and Edgware pages for street-level detail.

Haringey, Enfield, Camden, Islington and Hackney

Enfield has the clearest numbers (DMD 11: 3 m rear depth on a terrace or semi, 4 m detached, and a codified 45-degree test) and Article 4 directions in almost every conservation area. Haringey has no extensions SPD, judges daylight under the BRE guide, and inside its Muswell Hill, Crouch End and Highgate conservation areas requires permission for any roof addition and any rear extension over 3 m. Camden combines qualitative Home Improvements guidance with a 45-degree test and a borough-wide basement Article 4. Islington has Article 4 directions in 40 of 42 conservation areas and guidelines that rule out most visible roof extensions. Hackney approved a new Residential Extensions SPD in December 2025, in effect from January 2026 (3 m/3.5 m/4 m rear depths, codified 45-degree test) and generally refuses roof extensions on unaltered conservation-area rooflines. See our Enfield, Muswell Hill, Crouch End, Highgate, Islington and Stoke Newington pages.

Anderson's advice: talk to the neighbours before the planning notice does

Semi-detached hip-to-gable plus rear dormer combinations almost always fall under permitted development, but the party wall notice still lands next door. A conversation over the fence before the notice — and before the surveyor's letter — gets it signed in a week rather than a month.

What our clients say

“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. As before we are very happy with the services from Lccl and we highly recommend their design and construction services for both home extension or loft conversion including both design and build services.”

— Mia M, Google Reviews

As LABC Building Excellence Award winners in 2024 (Best Residential Extension in London, Bohun Grove EN4) and London Regional Winners in 2026 (Best Conversion or Alteration to an Existing Home, Weech Road NW6), every project is delivered by one team of architects, structural engineers, project managers and builders. Workmanship is guaranteed for 12 months from practical completion, with a 10-year LABC structural warranty.

Areas we cover

Dedicated pages for the areas we work in most:

• Barnet
• Finchley
• Enfield
• Edgware
• Hendon
• Mill Hill
• Muswell Hill
• Highgate
• Crouch End
• Islington
• Camden
• Stoke Newington

We also work across Southgate, Winchmore Hill, Palmers Green, Totteridge, Whetstone, Hadley Wood, East Barnet, Friern Barnet, Golders Green and Tottenham — the same team, the same contract and the same prices apply, and we survey every project in person before quoting.

To book a free consultation call LCCL Construction on 020 8037 7332 or get an instant estimate online. Get an instant estimate or book a free consultation call. Already have drawings? Send us the set.

One team, one contract, one point of contact — from first sketch to handover.