New Mills, Derbyshire
Semi-detached rear extension in New Mills
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in New Mills 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.
New Mills sits in Derbyshire, with postcode districts including SK22. Where a New Mills 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 New Mills?
A semi-detached rear extension in New Mills is priced at £1,840–£3,010 per square metre including VAT as a guide, before kitchen fit-out and fees. East Midlands prices sit a little below our West Midlands baseline.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £22,000–£36,000 |
| 4 m wide × 5 m deep (20 m²) | £37,000–£60,000 |
| 4 m wide × 6 m deep (24 m²) | £44,000–£72,000 |
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 New Mills?
Planning for a semi-detached rear extension in New Mills follows the English householder rules.
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 New Mills like to extend?
Red-brick terraces and semis are typical of New Mills. Coal-mining legacy areas in parts of the East Midlands can need a Coal Authority check before foundations are designed.
How a semi-detached rear extension in New Mills 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.
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 New Mills
Neighbouring places we cover include Marple (3.3 miles) and Poynton (4.9 miles).
- Semi-detached rear extension in Marple
- Semi-detached rear extension in Poynton
- Semi-detached rear extension in Hazel Grove
- Semi-detached rear extension in Glossop
- Semi-detached rear extension in Bredbury
Other work in New Mills:
FAQ
Semi-detached rear extension questions in New Mills
How much does a semi-detached rear extension cost in New Mills?
As a guide, £1,840–£3,010 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £22,000–£36,000 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.
How long does a semi extension take?
10 to 16 weeks on site for a single-storey extension.
Do you handle building control in New Mills?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.
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.
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.