Harrow on the Hill, Greater London
Single-storey rear extension in Harrow on the Hill
Ground-floor space across the back of the house, usually for a kitchen, dining or family room. If you live in Harrow on the Hill 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 Harrow on the Hill (HA1, HA2 and HA3) as part of our Greater London work. A single-storey rear extension in Harrow on the Hill 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 Harrow on the Hill?
Guide prices for a single-storey rear extension in Harrow on the Hill start from our London rate of £2,470–£4,030 per square metre, including VAT. London prices sit at the top of our range because of labour rates, access through the house, parking suspensions and skip licences.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £29,500–£48,500 |
| 4 m wide × 5 m deep (20 m²) | £49,500–£80,500 |
| 4 m wide × 6 m deep (24 m²) | £59,500–£96,500 |
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 single-storey rear extension in Harrow on the Hill?
The planning route for a single-storey rear extension in Harrow on the Hill 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.
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. We check your house's planning history and any conservation area before drawing, so the route is clear before you spend on plans.
What are homes in Harrow on the Hill like to extend?
Harrow on the Hill is mostly 1930s semis, short terraces and post-war houses, so full-width single-storey and two-storey rear extensions are realistic on many plots. Some later estates had permitted development rights removed by condition, so we check the planning history first.
How a single-storey rear extension in Harrow on the Hill 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.
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.
Single-storey rear extensions near Harrow on the Hill
Neighbouring places we cover include Harrow (0.5 miles) and Sudbury (1.2 miles).
- Single-storey rear extension in Harrow
- Single-storey rear extension in Sudbury
- Single-storey rear extension in Headstone
- Single-storey rear extension in Wealdstone
- Single-storey rear extension in Wembley
Other work in Harrow on the Hill:
FAQ
Single-storey rear extension questions in Harrow on the Hill
Do you handle building control in Harrow on the Hill?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.
Will I need a structural engineer?
Yes for the beam over the new opening and usually the foundations; we arrange them and their calculations go to building control.
Is a flat roof or a pitched roof better?
A warm flat roof keeps the extension low under first-floor windows and suits a roof lantern; a pitched or lean-to roof gives a vaulted ceiling. Both last for decades when built properly.
Is the site visit in Harrow on the Hill free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
How long does a rear extension take to build in Harrow on the Hill?
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 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.