House Extensions & Loft Conversions across North West London

LCCL Construction is a design and build company based in Finchley N3, working across North West London for over 20 years. One team, one contract: architects, structural engineers, project managers and builders coordinated by LCCL take your project from first sketch to handover.

North West London is where our LABC 2026 winner sits: Weech Road NW6 in Hampstead. The stock runs from Hampstead and St John's Wood villas and mansion flats to the Edwardian terraces of Kilburn and Queen's Park and the 1930s semis of Mill Hill and Hendon. Top-floor flats with roof space — as at Weech Road — are a speciality.

What it costs across North West 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)
• 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).

A recent LCCL project near North West London

Weech Road, Hampstead NW6 — penthouse duplex loft conversion

A top-floor flat turned into a penthouse duplex: the kitchen and living space moved up into the new loft, two new bathrooms, an extra bedroom and views across to the Shard, the London Eye and Parliament. LABC Building Excellence Awards 2026 London Regional Winner — Best Conversion or Alteration to an Existing Home.

See the project

Planning across North West London

Camden's conservation areas cover much of Hampstead and Belsize; Brent is more permissive in Kilburn and Queen's Park but has Article 4 directions in places; Barnet (Mill Hill, Hendon) is generally straightforward for permitted development. Leasehold flats need freeholder consent alongside planning — we build that into the programme.

Borough by borough

Camden covers Hampstead, Belsize, Swiss Cottage and Primrose Hill with conservation areas and 2010 Article 4 directions on front-facing changes, qualitative Home Improvements guidance, a codified 45-degree and 25-degree daylight test and a borough-wide basement Article 4 (in force 1 June 2017) with audited Basement Impact Assessments. Brent has the most generous numbers: its January 2025 extensions SPD accepts 6 m (attached) and 8 m (detached) single-storey rear extensions outside conservation areas, with the Queen’s Park conservation area and its Article 4 direction the main exception. Westminster in St John’s Wood has a 1967 conservation area where roof extensions are unlikely to be accepted and a city-wide basement Article 4 (31 July 2016). Barnet (Mill Hill, Hendon, Golders Green) applies its June 2026 SPD depths of 3 m, 3.5 m and 4 m, with Article 4 directions in Mill Hill, Hendon The Burroughs and Hampstead Garden Suburb. See our Hampstead, St John’s Wood, Queen’s Park, Mill Hill and Hendon pages.

Anderson's advice: put the rooflights over the island

Rooflights over kitchen islands transform natural light more than any other single design decision. We position them on the plan before the kitchen layout is fixed, not after.

What our clients say

“LCCL Constructions was professional, trustworthy and worked to the highest standard. The process was smooth and I'm very happy with the result - it has transformed the quality of my home.”

— KashImaging, Trustpilot

As LABC Building Excellence Award winners in 2024 (Best Residential Extension in London) and 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:

• Hampstead
• St John's Wood
• Queen's Park
• Mill Hill
• Hendon
• Edgware

We also work across West Hampstead, Kilburn, Cricklewood, Golders Green, Willesden, Kensal Rise, Colindale and Kingsbury — the same team, the same contract and the same price bands 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.

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