Lancing, West Sussex
Semi-detached rear extension in Lancing
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Lancing and want to know what a semi-detached rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
Lancing is covered from our West Sussex round, including BN15. In Lancing we measure the attached neighbour's extension at the survey, because it often sets the sensible depth for yours.
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 Lancing?
In Lancing, our guide for a semi-detached rear extension is £2,130–£3,470 per square metre including VAT for a standard specification. South East prices run above our West Midlands baseline, mainly on labour rates and clay-soil foundations.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £25,500–£41,500 |
| 4 m wide × 5 m deep (20 m²) | £42,500–£69,500 |
| 4 m wide × 6 m deep (24 m²) | £51,000–£83,500 |
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 for a semi-detached rear extension in Lancing?
The planning route for a semi-detached rear extension in Lancing 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.
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. 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 Lancing like to extend?
Commuter semis and detached houses make up much of Lancing, and longer gardens make England's prior approval route for deeper rear extensions worth considering.
How a semi-detached rear extension in Lancing comes together
Free site visit
We measure the house and garden, look at the back wall, drainage and boundaries, and talk through what you want from the space.
Drawings and budget
Floor plans and elevations for the options, each with a guide price.
Approvals
Permitted development check, prior approval or planning application, then Building Regulations drawings and structural calculations, plus party wall notices where they apply.
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 Lancing
From Lancing, the nearest places we also cover are Shoreham-by-Sea (2.1 miles) and Worthing (2.4 miles).
- Semi-detached rear extension in Shoreham-by-Sea
- Semi-detached rear extension in Worthing
- Semi-detached rear extension in Portslade
- Semi-detached rear extension in Hove
- Semi-detached rear extension in Brighton
Other work in Lancing:
FAQ
Semi-detached rear extension questions in Lancing
Can I get a price without a visit?
Our online guide-price tool gives a range in a couple of minutes. A written price needs a survey.
How long does a rear extension take to build in Lancing?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
Can I match pebbledash or render?
Yes. Many semis are refinished with new render across the whole back elevation so old and new match.
Can you match the brick or stone on my Lancing house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
Do I need planning permission for a rear extension in Lancing?
Often not for a single-storey rear extension of up to 3 metres (4 metres on a detached house) under permitted development, or up to 6 or 8 metres with prior approval, unless the house is in a conservation area or its rights have been removed.
How much does a semi-detached rear extension cost in Lancing?
As a guide, £2,130–£3,470 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £25,500–£41,500 at that rate. Your written price follows the survey.