How much does a house extension cost in London?

House extension costs in London typically range from £45,000 for a side return extension to £140,000+ for a large wraparound extension. Single-storey rear extensions average £65,000-£85,000 depending on size and specification. All our quotes are fixed-price with no hidden fees.

Do I need planning permission for a house extension?

Many extensions qualify for permitted development rights and don't require planning permission. Single-storey rear extensions up to 6m (terraced) or 8m (detached) often don't need permission. However, conservation areas and listed buildings have different rules. We provide free planning assessments.

How long does a house extension take to build?

A typical single-storey rear extension takes 12-14 weeks from start to completion. Side return extensions take 10-12 weeks, while wraparound extensions typically require 14-18 weeks. This includes all structural work, finishes, and final decoration.

Will an extension add value to my home?

Yes, a well-designed extension typically adds 15-25% to your property value. In South West London, this can represent a significant return on investment, especially for kitchen-diner extensions which are highly sought after by buyers.

What's included in your extension quote?

Our fixed-price quotes include foundations, structural work, steel beams, brickwork, roofing, windows/doors (including bi-folds), insulation, plastering, electrics, plumbing, flooring, and decoration. We also handle building regulations and structural engineer fees.

House Extensions South West London

Create the space you need with a beautifully designed house extension. Expert craftsmanship, seamless integration, and exceptional results.

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Why Choose Bluebird Spaces for Your Extension

Add Significant Value

Extensions can add 15-25% to your property value with the right design

12-16 Week Build

Efficient project management ensures timely completion

Design Excellence

Thoughtful designs that maximize light and space

FMB Accredited

Certified Federation of Master Builders member

Types of House Extensions

Side Return Extension

From £45,000

Perfect for Victorian and Edwardian terraces. Reclaim wasted side passage space and create an open-plan kitchen-diner.

Typically 3-4m x 6m (18-24m²)
Often permitted development
Transforms narrow kitchens
10-12 week build time

Single-Storey Rear Extension

From £65,000

The classic extension. Extends into your garden to create a spacious kitchen-dining area with bi-fold or sliding doors.

Typically extends 3-6m from house
Permitted development (usually up to 6m for terraced)
Floods space with natural light
12-14 week build time

Wraparound Extension

From £95,000

Combines side return and rear extension for maximum space. Creates impressive open-plan living areas.

Typically adds 40-60m²
May require planning permission
Transforms entire ground floor
14-18 week build time

What's Included in Our Extensions

Structural Work

Full foundations and groundwork
Steel beam installation
Brickwork and masonry
Roof structure and tiling

Windows & Doors

Bi-fold or sliding doors
Roof windows or lanterns
High-performance double glazing
External door frames

Internal Finishes

Plastering and decoration
Flooring installation
Skirting and architraves
Kitchen fit-out ready

Services & Compliance

Full electrical installation
Plumbing and heating
Building regulations approval
Structural engineer's design

Detailed Pricing Guide

Extension Costs by Type and Size

Side Return Extension (18-24m²)

Standard specification

£45,000 - £58,000

Single-Storey Rear (25-35m²)

Extending 4-5m with bi-folds

£65,000 - £85,000

Single-Storey Rear (40-50m²)

Extending 6m+ with roof lantern

£85,000 - £115,000

Wraparound Extension (50-70m²)

Combined side return and rear

£95,000 - £140,000

Additional Costs to Consider:

Kitchen supply & fit: £15,000 - £40,000
Party Wall Agreement: £700 - £1,500 per neighbour
Planning permission: £350 - £1,200 (if required)
Premium finishes: 15-25% additional cost

Note: All prices include VAT, building regulations, and structural engineer. Fixed price guaranteed.

How a house extension works

Free site visit and feasibility

We assess your garden, existing structure, drainage runs and any party wall implications. We advise on single storey, double storey or wraparound options and give a realistic budget range before any fees are paid.

No obligationFreeBudget range same day

What our clients say

Don't just take our word for it — hear from homeowners across SW London

"Tom was brilliant throughout the whole build process. It was a pleasure to be asked for a website review, after all they did for us. We are truly grateful to the whole team for the level of quality and for continually going the extra mile."

Rowan A

Wandsworth

"Bluebird was recommended to me by our local estate agent. Lovely guys and so pleased decided to go with them. Tom, Milen and the team on site were so professional and couldn't have been more helpful. Very happy clients."

Emma and Tom

Richmond

"The first project we trusted Tom and Milen with was a house conversion into 4 flats. We didn't know it at the time, but using Bluebird for such a big project was the best decision we have made. They are our first call when we find another development."

Tony and Rhys

Putney

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Ready to talk about your project?

Free consultation. Transparent, fixed-price quote within 48 hours.

Reach Out 07564 041115