London House Extensions FAQs

A house extension is an addition that increases the usable living space of your home by extending the existing structure. In London, this often means a rear extension, side-return extension, wraparound extension, kitchen extension or double-storey addition.

The most common London extension types are rear extensions, side-return extensions, wraparound extensions, kitchen extensions and double-storey extensions. Terraced and semi-detached homes often suit side-return and rear layouts because they improve narrow kitchens and create better garden connection.

A well-designed extension can improve both usable space and property value, especially when it creates a larger kitchen, better natural light, an extra bedroom or a more practical family layout. The final uplift depends on location, size, design quality and finish level.

Construction for a straightforward single-storey extension is often around 3–4 months, while larger or more complex projects can take longer. Design, planning permission, structural calculations and party wall matters can add extra time before building starts.

Many homeowners stay in the property during ground-floor extension work, but it depends on the scale of disruption, access, utilities and whether the kitchen or bathroom is affected. A good project plan should explain noise, dust control, temporary facilities and safety before work begins.

Before work begins, you should clear the working area, protect valuable items, confirm utility arrangements, agree access routes and make sure party wall, structural and Building Regulations requirements are in place.

A rear extension adds space to the back of your home, usually into the garden. It is commonly used to create a larger kitchen, dining room, family area or open-plan living space.

Many rear extensions may be possible under permitted development if they meet size, height and location limits. Larger extensions, double-storey schemes, conservation-area properties and listed buildings often need planning permission.

Rear extension costs vary based on size, foundations, steelwork, glazing, roof type, internal finishes and access. London projects with premium glazing, kitchens and finishes require a tailored quotation.

A single-storey rear extension often takes around 3–4 months on site, depending on design complexity, roof structure, glazing and finishes.

Common options include flat roofs with skylights, pitched roofs, gable roofs and roof lanterns. The best choice depends on the property style, desired light, ceiling height, cost and planning considerations.

It can if the extension affects light, privacy, boundary walls or foundations. Good design, early communication and party wall notices where needed help reduce neighbour issues.

A wraparound extension combines a side-return extension with a rear extension, creating an L-shaped addition that can completely transform the back of the house.

A wraparound extension creates a much larger open-plan space and is ideal for homeowners who want a premium kitchen, dining and family room with strong garden connection.

Wraparound extensions usually require full planning permission because they combine side and rear elements and often exceed permitted development limits.

Wraparound extensions are usually more expensive than simple rear or side-return extensions because they involve a larger footprint, more structure, more roofing, more glazing and more internal finishing.

A large wraparound project can take several months on site, with additional time for design, planning, party wall matters and structural coordination.

Extensions must meet Building Regulations covering structure, fire safety, insulation, ventilation, drainage, electrics, glazing and overall safety.

Yes, structural calculations are normally required where walls are removed, large openings are created, steel beams are installed or significant roof/foundation loads are introduced.

New walls, floors, roofs, windows and doors must meet current thermal performance standards. Good insulation improves comfort, reduces energy use and supports Building Control approval.

Extensions may require suitable smoke alarms, fire-safe routes, carbon monoxide alarms where relevant and compliant electrical work. The exact requirements depend on the layout.

Building Control usually inspects key stages such as foundations, drainage, structure, insulation and completion. A completion certificate should be issued when the work complies.

Design and build means one team manages both the design and construction process, giving you a single route from concept and approvals through to the finished extension.

Design and build can reduce miscommunication, improve cost control and make project delivery smoother because design, planning, structural coordination and construction are joined up.

The process usually starts with consultation and feasibility, then concept design, planning and technical drawings, structural calculations, quotation, construction, finishing and handover.

A proper design and build contractor coordinates the trades needed for the project, including builders, plumbers, electricians, plasterers, roofers, glazing installers and joiners.

Small changes may be possible, but late changes can affect cost and timescale. It is always better to finalise design and specification before work starts.

Quality is controlled through clear drawings, managed site stages, trade coordination, inspections, Building Control checks, snagging and final handover.