Knotty Ash, Merseyside
Single-storey rear extension in Knotty Ash
Ground-floor space across the back of the house, usually for a kitchen, dining or family room. If you live in Knotty Ash and want to know what a single-storey rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
We cover Knotty Ash (L13, L14 and L16) as part of our Merseyside work. A single-storey rear extension in Knotty Ash is mostly built from the garden side, so the house stays usable for most of the job.
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 Knotty Ash?
For Knotty Ash we work from the North West England rate: £1,790–£2,910 per square metre of new floor, including VAT, 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 |
These are guide ranges; the written quote after the survey is the figure that counts.
Do you need planning permission for a single-storey rear extension in Knotty Ash?
Planning for a single-storey rear extension in Knotty Ash 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 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 Knotty Ash like to extend?
Knotty Ash 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 single-storey rear extension in Knotty Ash 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.
Drawings and budget
Floor plans and elevations for the options, each with a guide price.
Planning and regulations
We take the design through the right planning route, then produce the construction drawings and engineer's calculations for building control.
Build and sign-off
We build to the approved drawings with regular updates, then hand over the building control completion certificate and any guarantees from suppliers.
Single-storey rear extensions near Knotty Ash
We also build single-storey rear extensions in nearby Old Swan (0.5 miles) and West Derby (1.3 miles).
- Single-storey rear extension in Old Swan
- Single-storey rear extension in West Derby
- Single-storey rear extension in Childwall
- Single-storey rear extension in Wavertree
- Single-storey rear extension in Norris Green
Other work in Knotty Ash:
FAQ
Single-storey rear extension questions in Knotty Ash
What postcode areas do you cover around Knotty Ash?
Including L13, L14 and L16, and the surrounding Merseyside area.
How long does a rear extension take to build in Knotty Ash?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
How deep can a single-storey rear extension be without planning?
In England, 3 metres on an attached house and 4 metres on a detached house under permitted development, or up to 6 and 8 metres with prior approval. Wales allows 4 metres; Scotland and Northern Ireland have their own limits.
How much does a single-storey rear extension cost in Knotty Ash?
As a guide, £1,790–£2,910 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £21,500–£35,000 at that rate. Your written price follows the survey.
Can you match the brick or stone on my Knotty Ash 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.