House Extensions & Loft Conversions in Wimbledon

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

Wimbledon and Raynes Park run from Victorian terraces near the town centre to large Edwardian and 1930s houses on the hill and in the village: side returns and rear dormers on the terraces, wraparounds, hip-to-gable lofts and full renovations on the larger stock.

What it costs in Wimbledon

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 Wimbledon

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 in Wimbledon

Merton runs standard householder and permitted-development routes; Wimbledon Village, Wimbledon North and John Innes Merton Park are conservation areas with planning permission needed for roof and front changes.

Conservation areas and Article 4 directions in Wimbledon

Merton has seven conservation areas in and around SW19 and SW20: Wimbledon Village, Wimbledon North (first designated as part of the Wimbledon conservation area in 1976 and subdivided in 1987 — “a spacious and verdant residential suburb of the 19th century and later” with a mixed palette of materials), Wimbledon West, Wimbledon Hill Road, Wimbledon Broadway, Wimbledon Chase and John Innes Merton Park. Householder Article 4 directions apply only in John Innes Merton Park and Wilton Crescent, so elsewhere front-facing replacement windows remain permitted development while roof extensions, side extensions and two-storey rear extensions in a conservation area need planning permission (a single-storey rear extension within the national 3 m or 4 m limit is still permitted development). Merton has also used Article 4 directions on small HMO conversions — seven wards from 17 November 2022 and, by an immediate direction on 24 March 2026, thirteen more including Wimbledon Park, Wimbledon Town, Dundonald, Village, Raynes Park and Hillside. The inter-war streets of Raynes Park and Wimbledon Park outside the conservation areas take lofts and rear extensions on a Lawful Development Certificate.

The rules Merton applies (Local Plan adopted 20 November 2024)

Merton’s new Local Plan superseded the older DM D2 and D3 standards with policy D12.4, which asks extensions to respect the form, scale, bulk and proportions of the original building, avoid long conjoined facades, keep dormers of an appropriate size and form and cause no significant overshadowing or overlooking. There is no fixed 45-degree rule; we design to the line as standard. Basements under policy D12.11 and the Basement and Subterranean Design SPD (March 2017) are single storey, extend beyond the original outer walls to no more than 50% of the original footprint, keep at least 1 m of soil over any part beyond the footprint, cannot go under a listed building or its garden, and need a Basement Impact Assessment; lightwells are engineering operations that need permission in their own right.

Fees and timescales

A householder application costs £548 (from April 2026, plus the Planning Portal charge) with an eight-week decision period. Merton’s householder pre-application advice is £250 including a 15-minute virtual meeting (£200 per further meeting), usually booked within ten working days; a written-only service is not offered. Party wall notices run alongside planning: two months’ notice for works to a shared wall, one month for excavations within 3 m or 6 m of a neighbour’s foundations.

Building control

Merton runs its own building control service. We use the council inspector on every project. Typical inspection points are commencement, foundation trenches, oversite and damp-proof course, drainage before backfill, structural steels and joists before they are covered, insulation and fire-stopping before plastering, then completion. We book each one and hand you the completion certificate at the end of the job.

Anderson's advice: talk to your neighbours before the notices go out

Semi-detached hip-to-gable plus rear dormer combinations almost always fall under permitted development, but neighbours often object informally. A conversation over the fence before the party wall notice lands avoids most of it.

What our clients say

“LCCL Construction were professional from start to finish. The team were trustworthy, reliable and delivered work to the highest standard.”

— 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 Warranty available to purchase.

Nearby areas

Wimbledon is part of our South West London guide. Nearby areas: Fulham, Clapham, Richmond, Putney & Wandsworth.

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.