Semi-detached rear extension in Thamesmead

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

In Thamesmead, 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.

Your written price follows a measured survey and an agreed design, so it reflects your house, not an average.

Do you need planning permission for a semi-detached rear extension in Thamesmead?

The planning route for a semi-detached rear extension in Thamesmead is set by England's householder rules and your council.

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. At the first visit we measure what is there now and tell you which route fits: permitted development, prior approval or a planning application.

What are homes in Thamesmead like to extend?

Much of Thamesmead is 1920s and 1930s semis and short terraces with longer gardens than inner London, which suit full-width single-storey rear extensions. Parking suspensions, skip licences and controlled hours on residential streets shape the programme more than the build itself.

How a semi-detached rear extension in Thamesmead comes together

1. Look round and measure

   A free visit to see the back of the house, measure it, check the drains and boundaries and hear what you need.

2. Options and costs

   We draw layout options and price each one, so the budget shapes the design rather than surprising you later.

3. Planning and regulations

   We take the design through the right planning route, then produce the construction drawings and engineer's calculations for building control.

4. Fixed price and build

   A written price for the agreed design, a start date and a named contact through the build, ending with the building control completion certificate.

Semi-detached rear extensions near Thamesmead

From Thamesmead, the nearest places we also cover are Abbey Wood (1.3 miles) and Belvedere (1.6 miles).

• Semi-detached rear extension in Abbey Wood
• Semi-detached rear extension in Belvedere
• Semi-detached rear extension in Plumstead
• Semi-detached rear extension in Barking
• Semi-detached rear extension in Welling

Other work in Thamesmead:

• Single-storey rear extension
• Two-storey rear extension
• Kitchen-diner rear extension
• Side return extension
• Wraparound extension
• Glazed rear extension

All rear extensions in Thamesmead