House Extensions South London 2026: Costs, Planning and What to Expect

House extensions in South London are one of the most popular ways homeowners across Clapham, Wandsworth, Putney, Dulwich, Brixton, Streatham, Tooting, Balham and surrounding areas add space and value to their properties. South London has a high concentration of Victorian and Edwardian terraced houses that are ideally suited to rear extensions, side return extensions, wraparound extensions and loft conversions. In 2026, a house extension in South London typically costs between £35,000 and £120,000 depending on type and specification.

LCCL Construction delivers house extensions across South London and surrounding areas

LCCL Construction is a design and build company based in Finchley, North London, delivering house extensions across the whole of London including South London and Hertfordshire. This guide covers everything you need to know about house extensions in South London — the best types for the area, typical costs, planning permission rules and what to expect from the process.

The Most Popular House Extensions in South London

Rear extension: The most common type across South London. Victorian and Edwardian terraced houses typically have a rear kitchen that can be extended 3 to 6 metres into the garden. A rear extension creates an open plan kitchen-diner — the most desirable living arrangement in London. Costs from £35,000.

Side return extension: Fills in the narrow side alley that runs alongside many South London terraced houses. Adds width to the ground floor and is almost always combined with a rear extension to create a wraparound. Costs from £35,000.

Wraparound extension: The most transformative ground floor extension. Combines a rear extension with a side return for an L-shaped addition that creates the maximum possible open plan space. Popular across Clapham, Wandsworth, Dulwich and Putney. Costs from £60,000.

Double storey extension: Adds space on both ground and first floors. Particularly cost-effective on larger South London semi-detached properties. Costs from £80,000.

How Much Do House Extensions Cost in South London in 2026?

House extension costs in South London are comparable to the rest of inner London. Labour costs are slightly higher in inner South London boroughs such as Lambeth, Southwark and Wandsworth than outer areas. As a general guide:

Rear extension (single storey, 3–6m): £35,000 to £60,000.

Side return extension: £35,000 to £65,000.

Wraparound extension: £60,000 to £100,000.

Double storey extension: £80,000 to £130,000.

All costs are estimates and depend on size, specification and exact location. A detailed written cost estimate is provided following a free site consultation.

Do You Need Planning Permission for a House Extension in South London?

Most single-storey rear extensions in South London fall within permitted development rights and do not require a full planning application. However, South London has a large number of conservation areas — particularly in Clapham, Dulwich, Brixton, Streatham, Wandsworth and Tooting — where permitted development rights are restricted and planning permission is required. LCCL Construction checks all planning requirements as part of our free initial consultation. See our full guide to planning permission for rear extensions in London.

Areas of South London We Cover

LCCL Construction delivers house extensions across all areas of South London including Clapham, Wandsworth, Putney, Balham, Tooting, Streatham, Dulwich, West Dulwich, East Dulwich, Peckham, Brixton, Herne Hill, Stockwell, Vauxhall, Kennington, Camberwell, Bermondsey, Deptford, Lewisham, Greenwich, Wimbledon, Raynes Park, Mitcham, Merton, Croydon, Norbury, Crystal Palace and surrounding areas.

How Long Does a House Extension Take in South London?

A single-storey rear extension in South London typically takes 10 to 14 weeks to build on site. The full project timeline from initial consultation to completion is usually 5 to 8 months. See our complete guide to how long a house extension takes in London for a full timeline breakdown.

How Much Value Does a House Extension Add in South London?

South London property values are high and house extensions add significant value. A rear extension that creates an open plan kitchen-diner typically adds £50,000 to £100,000 to the value of a South London terraced house. A wraparound extension can add £80,000 to £150,000 depending on location. In high-value areas such as Clapham, Wandsworth and Dulwich, the return on investment is particularly strong.

Why Choose LCCL Construction for Your South London House Extension?

LCCL Construction is an award-winning design and build company with over 20 years of experience delivering house extensions across London. We are LABC Award Winners 2024 for Best Residential Project, hold over 200 verified reviews at 4.7/5 and are members of the National Federation of Builders and LABC Registered Partners. We handle everything from architectural design and planning through to structural engineering, building regulations, party wall agreements and construction. To get a free consultation and detailed cost estimate for your South London house extension, call us on 020 8037 7332 or book online.

Frequently Asked Questions About House Extensions in South London

How much does a house extension cost in South London?

Costs range from £35,000 for a rear extension to £130,000 for a large double storey extension. All costs depend on size, specification and location.

Do I need planning permission for a house extension in South London?

Most single-storey rear extensions fall within permitted development rights. However, many South London properties are in conservation areas where planning permission is required. LCCL Construction checks this as part of the free initial consultation.

Does LCCL Construction work in South London?

Yes — LCCL Construction delivers house extensions across all of South London including Clapham, Wandsworth, Putney, Dulwich, Brixton, Streatham, Tooting, Balham, Peckham, Greenwich and all surrounding areas.