St Helens, Merseyside
Single-storey rear extension in St Helens
Ground-floor space across the back of the house, usually for a kitchen, dining or family room. We design, get the approvals for and build single-storey rear extensions in St Helens and the surrounding area, with one contract from the first survey to building control sign-off.
St Helens is covered from our Merseyside round, including WA9, WA10 and WA11. A depth of 3 to 4 metres keeps many single-storey rear extensions in St Helens within permitted development, subject to the house's planning history.
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 single-storey rear extension cost in St Helens?
A single-storey rear extension in St Helens is priced at £1,790–£2,910 per square metre including VAT as a guide, before kitchen fit-out and fees. 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 |
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 single-storey rear extension in St Helens?
Here is how the rules in England apply to a single-storey rear extension in St Helens.
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.
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 St Helens like to extend?
Stone and brick terraces are common around St Helens. Where houses back onto a ginnel or alley, deliveries can come in from the rear, which makes the build tidier.
How a single-storey rear extension in St Helens 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.
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.
Single-storey rear extensions near St Helens
Neighbouring places we cover include Haydock (2.4 miles) and Rainhill (2.7 miles).
- Single-storey rear extension in Haydock
- Single-storey rear extension in Rainhill
- Single-storey rear extension in Whiston
- Single-storey rear extension in Prescot
- Single-storey rear extension in Ashton in Makerfield
Other work in St Helens:
FAQ
Single-storey rear extension questions in St Helens
What postcode areas do you cover around St Helens?
Including WA9, WA10 and WA11, and the surrounding Merseyside area.
How long does a rear extension take to build in St Helens?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
Will the extension make the room behind it dark?
Not if it is designed well. Rooflights or a lantern over the old back room, and a wide opening into it, keep daylight reaching the middle of the house.
Do you handle building control in St Helens?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.
Can you match the brick or stone on my St Helens house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
Who will build my extension?
Vetted building teams working under contract to us. Your contract is with S&K Property Investments and Improvement Ltd for the design and the build.