Rear House Extension London and Hertfordshire
Award-winning rear house extensions designed and built by LCCL Construction. From architectural design through to construction and finishing — everything under one roof. Based in Finchley, London N3, serving London and Hertfordshire. LABC Award Winners 2024. 200+ reviews rated 4.7 out of 5. Prices from £35,000 for full design and build.
LABC Awards
Winners 2024
200+ Reviews
4.7 / 5 Rating
NFB Members
LABC Partners
What Is a Rear House Extension?
A rear house extension extends your home from the back of the property, creating additional ground floor living space. It is the most popular type of house extension in London because it works with almost every property type — terraced, semi-detached and detached houses — and most rear extensions fall under permitted development rights, meaning no planning permission is needed.
Rear extensions are typically used to create open-plan kitchen-diners, expand living rooms, add utility rooms or create ground floor bedrooms. They range from modest 3-metre projections to larger 6-metre extensions that can transform the entire ground floor of your home.
LCCL Construction is an award-winning design and build company based in Finchley, London N3, specialising in rear house extensions across London and Hertfordshire. With over 20 years of experience, more than 200 verified reviews rated 4.7 out of 5, and LABC Awards Regional Winners 2024 for Best Residential Extension in London, we deliver every stage of your rear extension under one roof.
How Much Does a Rear House Extension Cost in London?
Rear house extension costs in London typically range from £35,000 to £80,000 depending on the size, specification and complexity of the project. Here is a breakdown of typical costs in 2026:
Small rear extension (3 metres): £35,000 to £50,000 including design and build.
Medium rear extension (4 to 5 metres): £50,000 to £65,000 including design and build.
Large rear extension (6 metres): £60,000 to £80,000 including design and build.
These prices include architectural design, structural engineer calculations, building regulations, all construction work, electrics, plumbing, plastering and decoration. Planning permission applications, party wall agreements and kitchen fitting are additional costs where applicable.
Costs vary depending on your location within London and Hertfordshire. Properties in areas such as Hampstead, Highgate and St Albans may attract higher construction costs due to access constraints and conservation area requirements, while properties in Barnet, Finchley, Hendon, Edgware and Borehamwood tend to fall within the standard range.
Get an instant quote for your rear extension at lcclconstruction.co.uk or call us on 020 8037 7332 for a free consultation.
Do I Need Planning Permission for a Rear Extension?
Most single-storey rear extensions in London fall under permitted development rights and do not require a formal planning application. Under current permitted development rules, you can extend:
Up to 3 metres from the rear wall on a terraced or semi-detached house.
Up to 4 metres from the rear wall on a detached house.
Up to 6 metres on a semi-detached or terraced house and 8 metres on a detached house under the larger home extension scheme (prior approval required).
The extension must not exceed 4 metres in height, must not extend beyond the side elevation of the original house, and must use similar materials to the existing property. Building regulations approval is always required regardless of whether planning permission is needed.
Planning permission is required if your property is in a conservation area, is a listed building, is a flat or maisonette, or if the extension exceeds the permitted development limits. Areas across London and Hertfordshire with conservation restrictions include parts of Hampstead, Highgate, Muswell Hill, Hadley Wood, St Albans and Radlett.
LCCL Construction handles all planning applications and building regulations submissions as part of our design and build service. We also apply for lawful development certificates to give you formal confirmation that your extension is compliant.
What Is Included in Our Rear Extension Service?
Our full design and build rear extension service covers every stage of the project under one roof:
Free initial consultation and project assessment.
Measured building survey of your existing property.
Architectural design drawings including floor plans, elevations and sections.
Planning permission application or lawful development certificate.
Building regulations drawings and submission.
Structural engineer calculations.
Party wall agreements where required.
All construction work including foundations, steelwork, brickwork, roofing and drainage.
First and second fix electrics and plumbing.
Plastering, decoration and finishing.
Final building control sign-off and completion certificate.
Optional 10-year LABC structural warranty.
Every project is managed by an experienced LCCL Construction project manager from start to finish. We are LABC Registered Partners and members of the National Federation of Builders, so every rear extension we build meets the highest standards of quality and compliance.
How Long Does a Rear House Extension Take?
A typical rear house extension takes 10 to 16 weeks to build depending on the size and complexity. The full project timeline including design and approvals is usually 4 to 6 months from initial consultation to completion:
LCCL Construction works to minimise disruption throughout the build. Most rear extensions are built from the outside in, so you can continue living in your home during construction.
Rear Extension Design Ideas
A well-designed rear extension can transform how you use your home. Popular design features for rear extensions in London include:
Open-plan kitchen-diners that connect indoor and outdoor living through bi-fold or sliding doors.
Flat roof extensions with skylights and roof lanterns to flood the space with natural light.
Vaulted ceilings to create a sense of height and space in single-storey extensions.
Seamless flooring that continues from the existing house into the new extension.
Integrated utility areas and storage solutions.
Underfloor heating for consistent warmth across the new space.
Our architectural design team works with every client to create a scheme that maximises space, light and functionality while complementing the character of your existing property. We have extensive experience designing rear extensions for Victorian terraced houses, Edwardian semis, 1930s properties and modern homes across London and Hertfordshire.
Areas We Cover for Rear House Extensions
LCCL Construction designs and builds rear house extensions across London and Hertfordshire. We have particular expertise in the following areas:
North London: Barnet, Finchley, Hendon, Muswell Hill, Highgate, Hampstead, Southgate, Enfield, Edgware, Totteridge, Whetstone, Friern Barnet, East Barnet, Crouch End, Wood Green, Palmers Green.
West London: Ealing, Chiswick, Acton, Hammersmith, Shepherds Bush.
South London: Clapham, Putney, Wandsworth, Dulwich, Lewisham, Eltham, Greenwich.
East London: Hackney, Stratford, Walthamstow, Stoke Newington.
Central London: Camden, Islington, Kensington, Westminster.
Hertfordshire: Borehamwood, St Albans, Potters Bar, Bushey, Watford, Radlett, Elstree, Hadley Wood.
Call us on 020 8037 7332 or visit lcclconstruction.co.uk to book a free consultation.
Frequently Asked Questions
Can I live in my house during a rear extension?
Yes. Most rear extensions are built from the outside and the opening into your existing house is one of the last stages. There will be some disruption but you do not usually need to move out.
Will a rear extension add value to my home?
Yes. A well-designed rear extension typically adds 5% to 15% to the value of a London property. For a home worth £500,000, that could mean £25,000 to £75,000 in added value — often exceeding the cost of the extension.
Do I need a party wall agreement for a rear extension?
If your extension is built up to or on the boundary with a neighbouring property, you will need a party wall agreement under the Party Wall Act 1996. LCCL Construction manages the party wall process on your behalf.
What is the maximum size rear extension without planning permission?
Under standard permitted development, 3 metres for terraced and semi-detached houses, 4 metres for detached. Under the larger home extension scheme, up to 6 metres for terraced and semi-detached and 8 metres for detached (prior approval required).
How do I get started?
Call us on 020 8037 7332, book a free consultation at lcclconstruction.co.uk, or get an instant quote online.