House Extensions & Loft Conversions across Central London

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

Central London work is mostly period property: Georgian and Victorian terraces in Islington and Camden, stucco villas and mansion flats in Kensington & Chelsea and Notting Hill, mews houses in Westminster. Space is tight, access is tighter, and the value of every square metre is high — which is why basements, loft conversions and full renovations dominate here rather than large footprints.

What it costs across Central 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).

Recent LCCL projects near Central London

Grosvenor Avenue, Highbury N5 — rear extension

A rear extension to an Edwardian terrace in Highbury: a new kitchen and dining space with underfloor heating, taken through Islington planning with drainage modifications the planners asked for, and a party wall agreement on one side.

See the project

Also nearby: Boundary Road NW8 (basement, renovation, 2023) · Tetcott Road, Chelsea SW10 (wraparound extension, renovation, 2025).

Planning across Central London

Expect conservation areas almost everywhere, Article 4 directions removing some permitted-development rights, and listed buildings in the older squares. Kensington & Chelsea and Westminster scrutinise basements closely (construction method statements, party wall awards, traffic management). Our architects prepare heritage statements and pre-application submissions as standard for these boroughs.

Permitted development in Central London: what goes ahead without a planning application

Mostly a planning application. Islington has Article 4 directions in 40 of 42 conservation areas, Kensington & Chelsea has more than 200 street-specific ones, Westminster and Camden require permission for every basement and resist visible roof extensions in their conservation areas; most Central London schemes go through a householder application, which we handle. On the streets outside the directions, a rear dormer or 3 m rear extension still goes ahead without one. Flats and maisonettes have no permitted development rights, whatever the street, and inside any conservation area a dormer or roof enlargement needs a planning application even where a single-storey rear extension within the limits does not.

On a house outside those streets, a rear dormer loft (40 m³ on a terrace, 50 m³ on a semi or detached house), a hip-to-gable, a single-storey rear extension of 3 m (4 m on a detached house) and a side-return infill are permitted development, and we apply for a Lawful Development Certificate on every one so the position is confirmed in writing. See our fixed-price permitted development projects — from £32,400 inc. VAT (£27,000 + VAT) for a Velux loft and £42,000 inc. VAT (£35,000 + VAT) for a 3 m rear extension, design and build inclusive, postcode dependent. Not sure whether your project needs a planning application?

Planning check

Borough by borough

Kensington & Chelsea protects nearly three quarters of the borough in 38 conservation areas, has more than 200 street-specific Article 4 directions and requires full planning permission for every basement (Article 4 in force 28 April 2016; policy CD11 limits basements to one storey, 50% of the garden and 1 m of soil cover). Westminster has 56 conservation areas, a city-wide basement Article 4 (31 July 2016) and City Plan policy 45 on similar lines. Camden adds a borough-wide basement Article 4 (1 June 2017) with audited Basement Impact Assessments and 2010 Article 4 directions across Hampstead and Belsize. Islington has Article 4 directions in 40 of its 42 conservation areas and conservation guidelines that rule out most visible roof extensions. Pre-application advice ranges from £456 (Westminster) to £559 (RBKC) for a written householder response. See our Kensington & Chelsea, Notting Hill, St John’s Wood, Camden and Islington pages.

Anderson's advice: start the party wall process early

Most clients underestimate the party wall timeline — it can add three months to a semi-detached or terraced project. We raise it at the first meeting so notices go out while the design is still being finalised, not after.

What our clients say

“Alex is super professional and on the ball at all times. He always thinks ahead and won't let you down. All his teams, from bricklayers, carpentry to electrics, roofing, tiling, painting, flooring and plumbing are excellent and hard working. They are all friendly yet professional. They are conscientious and want the job to be well done.”

— Ludovic, Reviews.io

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:

• Islington
• Camden
• Kensington & Chelsea
• Notting Hill
• St John's Wood

We also work across Westminster, Marylebone, Maida Vale, Bayswater, Holland Park, Pimlico, Bloomsbury and Clerkenwell — 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.

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