Lee, Greater London
Semi-detached rear extension in Lee
Thinking about a semi-detached rear extension in Lee? Single or two-storey extensions for semi-detached houses, with side access and one party wall. Our team handles the drawings, the planning route and the build, and your contract is with one company throughout.
We cover Lee (SE3, SE12 and SE13) as part of our Greater London work. Semi-detached houses are common across Greater London, and their side access makes rear extensions quicker to build.
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 Lee?
Guide prices for a semi-detached rear extension in Lee start from our London rate of £2,470–£4,030 per square metre, including VAT. 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 Lee?
Here is how the rules in England apply to a semi-detached rear extension in Lee.
In England a single-storey rear extension can often be built under permitted development: up to 3 metres beyond the original rear wall of an attached house, or 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres if any part 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. Before any drawing we look up the property's history with the council, because earlier extensions and removed rights change the answer.
What are homes in Lee like to extend?
Much of Lee is Victorian and Edwardian terraced housing with narrow back additions, which suits side returns, wraparounds and 3 metre rear extensions. Many streets are in conservation areas, gardens are short, and almost everything comes through the house or along a rear alley.
How a semi-detached rear extension in Lee 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.
Design and guide price
Two or three layout options with a guide price for each, so you choose the design knowing what it costs.
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 Lee
Close by, we work in Blackheath, about 0.6 miles away, and Ladywell, about 1.2 miles away.
- Semi-detached rear extension in Blackheath
- Semi-detached rear extension in Ladywell
- Semi-detached rear extension in Kidbrooke
- Semi-detached rear extension in Catford
- Semi-detached rear extension in Greenwich
Other work in Lee:
FAQ
Semi-detached rear extension questions in Lee
Do you handle building control in Lee?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.
Is the site visit in Lee free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
How long does a semi extension take?
10 to 16 weeks on site for a single-storey extension.
How much does a semi-detached rear extension cost in Lee?
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 I live at home while the extension is built?
Usually yes. Most of the work is outside until the back wall is opened near the end, and that stage is screened off.
Can you match the brick or stone on my Lee house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.