Extension prices and London house values by borough

What an extension adds to a home depends on local values. Here are the official figures by borough.

Average prices, July 2026

HM Land Registry figures for July 2026: Kensington and Chelsea £1,232,640; Westminster £876,788; Camden £815,159; Richmond upon Thames £803,249; Hammersmith and Fulham £738,048; Ealing £585,216; Croydon £390,041; Barking and Dagenham £375,604. The London average was £550,000. ^{[1] [2]}

How big without planning permission

Under permitted development, a single-storey rear extension can go up to 3 metres beyond the original rear wall (4 metres for a detached house), or up to 6 and 8 metres through the prior approval process. It cannot be more than 4 metres high. ^[3]

Levy on large extensions

The Planning Portal notes that an extension adding over 100 square metres of floor space may be liable for the Community Infrastructure Levy, which should be budgeted for. ^{[3] [4]}

Where we work

Extension pricing across London

We visit homes in every London borough to measure up and price extensions.

Costs are shaped by things that vary across the capital, such as access for materials, parking and skip permits, and how much space there is around the house.

Whichever borough you live in, the quote is built from a visit to your property.

Measure-and-price visits take place at your home, anywhere in London.

Boroughs we visit

Barking and Dagenham
Barnet
Bexley
Brent
Bromley
Camden
City of London
Croydon
Ealing
Enfield
Greenwich
Hackney
Hammersmith and Fulham
Haringey
Harrow
Havering
Hillingdon
Hounslow
Islington
Kensington and Chelsea
Kingston upon Thames
Lambeth
Lewisham
Merton
Newham
Redbridge
Richmond upon Thames
Southwark
Sutton
Tower Hamlets
Waltham Forest
Wandsworth
Westminster

Sources

Figures checked 15 October 2026. For general information; it is not advice on your property.

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