Southgate, Greater London
Semi-detached rear extension in Southgate
For homes in Southgate, a semi-detached rear extension is often the simplest way to gain space without moving. Single or two-storey extensions for semi-detached houses, with side access and one party wall. We take it from survey to completion certificate.
Southgate sits in Greater London, with postcode districts including N13, N21 and N22. Where a Southgate semi already has a small lean-to at the back, we usually replace it rather than extend it.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a semi-detached rear extension cost in Southgate?
For Southgate we work from the London rate: £2,470–£4,030 per square metre of new floor, including VAT, standard specification. London prices sit at the top of our range because of labour rates, access through the house, parking suspensions and skip licences.
| 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 |
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 Southgate?
Here is how the rules in England apply to a semi-detached rear extension in Southgate.
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.
If 3 or 4 metres is not enough, England's prior approval route allows 6 metres on a terraced or semi-detached house and 8 metres on a detached house for a single-storey rear extension. Neighbours are consulted, the council decides within 42 days, and the fee is £249, rising to £310 from 8 December 2026.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. We check your house's planning history and any conservation area before drawing, so the route is clear before you spend on plans.
What are homes in Southgate like to extend?
Period terraces in Southgate sit alongside flats, and the difference matters: houses usually keep permitted development rights, while flats and maisonettes need planning permission for any rear extension.
How a semi-detached rear extension in Southgate comes together
Survey visit
We visit free of charge, measure up, check access, drainage and neighbours' extensions, and note what you want the room to do.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
Planning and regulations
We take the design through the right planning route, then produce the construction drawings and engineer's calculations for building control.
Written price, then build
Once the design and approvals are in place, you get a fixed written price and programme, and we build through to sign-off.
Semi-detached rear extensions near Southgate
From Southgate, the nearest places we also cover are Palmers Green (0.4 miles) and Wood Green (1.4 miles).
- Semi-detached rear extension in Palmers Green
- Semi-detached rear extension in Wood Green
- Semi-detached rear extension in Tottenham
- Semi-detached rear extension in Edmonton
- Semi-detached rear extension in Northumberland Park
Other work in Southgate:
FAQ
Semi-detached rear extension questions in Southgate
What postcode areas do you cover around Southgate?
Including N13, N21 and N22, and the surrounding Greater London area.
How long does a rear extension take to build in Southgate?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
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.
How much does a semi-detached rear extension cost in Southgate?
As a guide, £2,470–£4,030 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £29,500–£48,500 at that rate. Your written price follows the survey.
Can you match the brick or stone on my Southgate house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
Do you handle building control in Southgate?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.