What types of house extension do you build in London?

BL Builders builds all types of house extension in London: single storey rear extensions, double storey extensions, side return extensions, wrap-around extensions, infill extensions, and over-garage extensions.

Will a house extension add value to my home?

Yes. A well-designed house extension in London typically adds between 10–20% to the property's value. Kitchen extensions, open-plan living spaces, and additional bedrooms command the highest uplifts in London's housing market.

House Extensions London | Rear, Side & Double Storey

Open-plan kitchen extension with skylights in London home

London's Extension Experts

Why Extend Rather Than Move?

With London property prices at a premium, extending your existing home is almost always more cost-effective than moving. A well-designed extension adds usable square footage, improves how your family lives day-to-day, and adds significant value to your property.

BL Builders have been building house extensions across London for over 25 years. Our team manages the entire project — from initial design and planning through to structural work, fit-out, and final Building Regulations sign-off.

Full architectural design service included where required
Planning permission applications handled on your behalf
Structural engineers, drainage, and electrics all coordinated
10-year structural guarantee on all extension work
Transparent, itemised quotes — no hidden costs

Get a Free Quote

Extension Types

House Extension Options in London

Every property is different. We advise on the best extension type for your home, planning situation, and budget.

Single Storey Rear Extension

The most popular London extension. Extends your kitchen or living room into the garden, typically creating an open-plan kitchen-diner with skylights and bi-fold doors.

From £25,000

Double Storey Extension

Adds a ground floor extension below and an extra bedroom (or bathroom) above. Maximises added square footage for the cost versus two separate builds.

From £45,000

Side Return Extension

Fills in the narrow side passage of a terraced or semi-detached property. Transformative for Victorian terraces — typically widens the ground floor by 2–3 metres.

From £28,000

Wrap-Around Extension

Combines a rear extension with a side return to create the maximum possible ground floor footprint. Delivers a dramatic transformation for Victorian terraced houses.

From £50,000

Over-Garage Extension

Adds a room above an existing integral or attached garage — typically converting it to a bedroom, study, or bathroom without reducing garden space.

From £30,000

Infill / Courtyard Extension

Fills in an internal corner or courtyard space to create additional living area. Often used to connect two wings of a house with a glass atrium or utility space.

From £20,000

Our Work

House Extension Projects in London

Recent extension projects completed by BL Builders across London.

Rear kitchen extension with bifold doors and skylights — Hackney, East London

Open-plan rear extension — Hackney, East London

Side return extension creating open-plan kitchen — Islington, North London

Side return extension — Islington, North London

Double storey extension with contemporary glazing — Wandsworth, South London

Double storey extension — Wandsworth, South London

Our Process

How Your House Extension Works

1

Free Design Consultation

We visit your property to assess the space, discuss your vision and advise on the best extension type. We also review your Permitted Development rights and any planning requirements.

2

Design & Planning

Our team prepares architectural drawings and handles planning applications or Permitted Development notifications with your local London council on your behalf.

3

Detailed Fixed Quote

You receive a fully itemised written quote covering all labour, materials, drainage, electrics, and finishes. No surprises — what we quote is what you pay.

4

Build & Sign-Off

Your dedicated project manager runs the build on schedule. We obtain all Building Regulations sign-offs and hand over a fully snagged, complete space.

Coverage

House Extensions Across All London Boroughs

We build house extensions throughout all of Greater London.

HackneyIslingtonSouthwark LambethWandsworthEaling HammersmithBarnetHaringey LewishamGreenwichTower Hamlets Waltham ForestBrentHounslow RichmondKingstonMerton CroydonBromleyCamden WestminsterNewhamRedbridge

Common Questions

House Extension FAQs

How much does a house extension cost in London?

House extension costs in London range from £15,000 for a small single storey rear extension to £80,000+ for a large double storey wrap-around. Average single storey rear extensions cost £25,000–£45,000. We provide a free, fully itemised written quote.

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

Many single storey rear extensions fall under Permitted Development and don't require planning permission, provided they meet size and height limits. Double storey extensions and extensions in Conservation Areas or on listed buildings typically require full planning permission. We advise on this during your free consultation.

How long does a house extension take to build in London?

A single storey rear extension takes 8–14 weeks from groundworks to completion. A double storey extension takes 12–20 weeks. Larger wrap-around extensions with complex rooflines may take 16–24 weeks. All timelines are given in your written quote.

Can I stay in my home during the extension build?

Yes. The majority of our London extension builds are carried out while the homeowner is in residence. We plan the work to maintain access to essential rooms and minimise disruption. Temporary weatherproofing ensures your home is secure during every stage.

Will a house extension add value to my London home?

Yes. A well-designed house extension typically adds 10–20% to a London property's value. Open-plan kitchen extensions, additional bedrooms, and home offices generate the highest returns in London's current housing market.

Expert House Extensions in London