Rear House Extension London 2026: Complete Guide by LABC Award Winners

By Anderson & the LCCL Construction Team | Finchley N3

A rear house extension is the most popular way to add ground floor space to a London home — extending directly out into the garden to create a larger kitchen, dining and living area. As LABC Building Excellence Award Winners 2024 for Best Residential Extension in London, LCCL Construction has delivered hundreds of rear extensions across London and Hertfordshire. This guide covers rear extension costs, design considerations, planning permission and includes a real East Barnet EN4 full renovation case study incorporating a rear extension.

LCCL Construction — LABC Award Winners 2024 for Best Residential Extension in London

A Real LCCL Rear Extension Project: East Barnet EN4

One of our completed projects at Bohun Grove in East Barnet EN4 shows what a well-executed rear extension delivers as part of a full home transformation. The scope included a new hip to gable loft conversion, a rear house extension creating open plan kitchen space, landscaping, a regulated outbuilding, new windows throughout, two Lusso Stone luxury bathrooms, enlarged bedrooms, floor-to-ceiling windows, skylights and premium finishes including Buster + Punch lighting. The rear extension itself transformed the ground floor from a compartmentalised traditional layout into a bright, connected family space opening onto a redesigned garden. Complete design and build delivery from concept to handover.

Rear Extension Costs in London 2026

Small rear extension (12-15 sqm): £42,000 – £66,000 inc. VAT (£35,000 – £55,000 + VAT). Standard rear extension (18-25 sqm): £54,000 – £78,000 inc. VAT (£45,000 – £65,000 + VAT). Large rear extension (28-40 sqm): £66,000 – £90,000 inc. VAT (£55,000 – £75,000 + VAT). Premium finish, roof lantern, bifold doors and structural glazing add £9,600 – £30,000 inc. VAT (£8,000 – £25,000 + VAT). The final figure depends on postcode, access and site conditions — the instant estimate applies your area. See our full rear extension cost guide.

Anderson's Advice: Rooflights Change Everything

From 20 years of rear extension delivery: rooflights over kitchen islands transform natural light more than any other single design decision. A well-positioned roof lantern or run of skylights above the working kitchen area brings light down onto the surfaces where you actually need it, at the times of day you use the kitchen most. Combined with bifold or sliding doors at the rear, a rear extension with proper rooflight positioning feels dramatically bigger and lighter than the same-sized extension without them. Budget for rooflights early — they're not an add-on, they're the design.

Rear Extension Planning Permission in London

Single storey rear extensions can fall within permitted development — up to 3 metres deep for terraced or semi-detached, or up to 6 metres under the Larger Home Extension prior approval scheme. Conservation areas, Article 4 directions and listed buildings require full planning permission. Party wall agreements are typically required for terraced and semi-detached properties. See our planning permission guide.

How Much Value Does a Rear Extension Add?

On our projects and local sold prices, a well-planned project of this kind usually adds more to the value of the home than it costs to build — see our guide on how much value an extension adds. A £66,000 inc. VAT (£55,000 + VAT) rear extension typically adds £85,000-£140,000 in outer London and £110,000-£180,000+ in premium locations. See our guide on how much value an extension adds.

What Our Clients Say

"Super professional and on the ball at all times. All his teams are excellent and hard working. They are conscientious and want the job to be well done." — Ludovic, Reviews.io

Why Choose LCCL Construction?

Finchley N3 based, covering all of London and Hertfordshire. Over 20 years of experience. 200+ verified reviews rated 4.7/5. LABC Building Excellence Award Winners 2024 for Best Residential Extension in London. LABC Registered Partners. NFB members. One team, one contract, one point of contact — from first sketch to handover.

Frequently Asked Questions

How much does a rear house extension cost in London?

From £42,000 inc. VAT (£35,000 + VAT) for a small rear extension to £90,000 inc. VAT (£75,000 + VAT) for a large rear extension with premium specification.

How long does a rear extension take?

Typically 10-16 weeks on site plus 8-16 weeks upfront for design and planning.

To book a free consultation call LCCL Construction on 020 8037 7332 or get an instant quote online.