House Extensions & Loft Conversions across South West London

LCCL Construction is a design and build company based in Finchley N3, working across South 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.

South West London's Victorian and Edwardian terraces — Clapham, Balham, Putney, Fulham, Wimbledon — are the classic side-return and rear-extension territory, and the roofs suit rear dormers and L-shaped dormers. Richmond adds larger semis and detached houses where wraparound extensions and hip-to-gable lofts come into play.

What it costs across South West London

Inner London — typically +10–15% on base prices. 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: £29,500–£48,500
• Rear dormer loft: £51,500–£77,000
• L-shaped dormer: £54,000–£94,500
• Hip to gable: £55,000–£109,000
• Mansard: £70,500–£142,500
• Rear extension: £38,500–£86,000
• Side return: £38,500–£89,500
• Wraparound: £66,000–£147,000
• Double storey: £82,500–£189,500

Kitchen fit-out on top of the structure: +£15,000–£75,000. Basements: cellar refit £45k–£95k, lowering £95k–£180k, new dig £180k–£300k+. New build: £2,200–£4,500 per sqm.

A recent LCCL project near South 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 South West London

Wandsworth is one of the more constructive planning departments to deal with at pre-application stage; Lambeth and Merton run standard permitted-development and householder routes; Richmond has many conservation areas and its own design guidance. Terraces mean a party wall award on both sides is the norm.

Borough by borough

Wandsworth (Local Plan July 2023) keeps its extension guidance qualitative, judges daylight under the BRE guide, and offers the cheapest advice of the boroughs we work in (£146 written pre-app, free duty planner). Lambeth applies its August 2023 Design Guide — rear dormers only, mansards generally not in conservation areas, basements keeping 70% of the garden — with no Article 4 directions on the Clapham areas. Merton (Local Plan November 2024) uses qualitative policy D12.4 for extensions and D12.11 for basements. Richmond (Local Plan October 2025) has 72 conservation areas, street-level Article 4 directions and a 2015 SPD with 3 m/3.5 m/4 m rear depths. Hammersmith & Fulham guides rear extensions to 3.5 m, applies a 45-degree test and requires permission for every basement (Article 4 in force 26 April 2018). See our Putney & Wandsworth, Clapham, Wimbledon, Richmond and Fulham pages.

Anderson's advice: use pre-application advice where the council engages

Wandsworth planning is much more helpful on pre-application than Islington in our experience. Where a council engages, a pre-app saves weeks; where it does not, a well-argued application with precedent cases works better.

What our clients say

“The Lccl construction team built my extension with a quick and clean service, they worked non stop through the winter weather.. I would highly recommend this company!”

— Chris Dunn, Google Reviews

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 Warranty available to purchase.

Areas we cover

Dedicated pages for the areas we work in most:

• Clapham
• Putney & Wandsworth
• Fulham
• Richmond
• Wimbledon

We also work across Balham, Battersea, Tooting, Streatham, Earlsfield, Barnes, Kingston and Twickenham — 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.