Greater London

Rear extensions for semi-detached houses in Greater London

Single or two-storey extensions for semi-detached houses, with side access and one party wall. Across Greater London we handle the whole rear extension: survey, drawings, the planning route, building control and the build. Towns we cover here include Islington, Bexley and Barking.

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Modest single-storey rear extension in red brick with white French doors on a semi-detached house

Semi-detached houses are common across Greater London, and their side access makes rear extensions quicker to build. Greater London is mostly 1930s semis, short terraces and post-war houses, so full-width single-storey and two-storey rear extensions are realistic on many plots. Some later estates had permitted development rights removed by condition, so we check the planning history first.

How much does a semi-detached rear extension cost in Greater London?

In Greater London, our guide for a semi-detached rear extension is £2,470–£4,030 per square metre including VAT for a standard specification. London prices sit at the top of our range because of labour rates, access through the house, parking suspensions and skip licences.

Semi-detached rear extension guide prices in Greater London
Size	Guide price inc VAT
3 m wide × 4 m deep (12 m²)	£29,500–£48,500
4 m wide × 5 m deep (20 m²)	£49,500–£80,500
4 m wide × 6 m deep (24 m²)	£59,500–£96,500

Ground conditions, glazing, the roof and how far the house is opened up move the final figure within the range.

Do you need planning permission in Greater London?

Under England's householder permitted development rules you can usually add 3 metres at the back of an attached house, or 4 metres on a detached house, without a planning application, as long as the extension stays under 4 metres high and its eaves stay under 3 metres where it is within 2 metres of a boundary.

A two-storey rear extension can be permitted development in England only if it projects no more than 3 metres, stays at least 7 metres from the rear boundary, matches the existing roof pitch and has obscure-glazed upper side windows. In practice most double-storey rear extensions go through a householder planning application.

England also has the larger home extension route: a single-storey rear extension of up to 6 metres on an attached house or 8 metres on a detached house, after prior approval from the council. The council notifies your neighbours and has 42 days to decide; the fee is £249 (£310 for applications made from 8 December 2026). The route is not available on designated land such as conservation areas.

Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent.

Where in Greater London do we work?

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FAQ

Questions people ask

How far can I extend a semi without planning?

3 metres under permitted development in England, or up to 6 metres with prior approval, outside designated land.

Can I match pebbledash or render?

Yes. Many semis are refinished with new render across the whole back elevation so old and new match.

Single or two-storey on a semi?

Two-storey if you need bedrooms, single-storey if you need a bigger kitchen. Planning risk is lower for single-storey.

Do you cover all of Greater London?

We cover 187 towns and districts in Greater London, including Islington, Bexley and Barking.

Who builds the extension?

Vetted building teams working under contract to us; your contract is with S&K Property Investments and Improvement Ltd.