Thornton-Cleveleys, Merseyside
Semi-detached rear extension in Thornton-Cleveleys
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Thornton-Cleveleys 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.
Thornton-Cleveleys and its postcode districts FY5, FY6 and FY7 are part of our Merseyside coverage. Where a Thornton-Cleveleys 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 Thornton-Cleveleys?
In Thornton-Cleveleys, our guide for a semi-detached rear extension is £1,790–£2,910 per square metre including VAT for a standard specification. North West prices sit below our West Midlands baseline; access on terraced streets is the main variable.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £21,500–£35,000 |
| 4 m wide × 5 m deep (20 m²) | £35,500–£58,500 |
| 4 m wide × 6 m deep (24 m²) | £43,000–£70,000 |
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 Thornton-Cleveleys?
The planning route for a semi-detached rear extension in Thornton-Cleveleys 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.
England's rules allow a rear extension of more than one storey without an application only when it is no deeper than 3 metres and at least 7 metres from the boundary opposite the rear wall, and never on designated land. Most two-storey schemes need householder planning permission.
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 Thornton-Cleveleys like to extend?
Thornton-Cleveleys has long runs of terraced houses with back yards and alleys, plus 1930s semis further out. Yard extensions on terraces are often single-storey and close to both boundaries.
How a semi-detached rear extension in Thornton-Cleveleys 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.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
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 Thornton-Cleveleys
Neighbouring places we cover include Cleveleys (0.8 miles) and Poulton-le-Fylde (3.2 miles).
- Semi-detached rear extension in Cleveleys
- Semi-detached rear extension in Poulton-le-Fylde
- Semi-detached rear extension in Fleetwood
- Semi-detached rear extension in Blackpool
- Semi-detached rear extension in Lytham St Annes
Other work in Thornton-Cleveleys:
FAQ
Semi-detached rear extension questions in Thornton-Cleveleys
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.
Do I need planning permission for a rear extension in Thornton-Cleveleys?
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.
Do I need a party wall agreement?
Usually with the attached neighbour, in England and Wales.
Is the site visit in Thornton-Cleveleys free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
Can you match the brick or stone on my Thornton-Cleveleys 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 a party wall agreement?
In England, usually yes if the extension is on or near a shared boundary or the foundations are close to a neighbour's building. We serve the notices.