Two-storey wraparound extensions in Harrow on the Hill

Useful details for planning a two-storey wraparound extension in Harrow on the Hill.

Postcode districts: HA2
County / area: Greater London, England
Price region: London
Guide price: £144,500–£198,000 (£2,580–£3,540 per m²)
Approval route: Planning permission is needed: the side part takes it outside permitted development in England.
Nearest towns: Harrow (0.5 miles), Sudbury (Greater London) (1.2 miles), Brent (1.9 miles)
First visit: Free, no obligation

About a two-storey wraparound extension

A two-storey wraparound extension is an L-shaped addition that extends both the side and the rear of your house, on two floors. It gives one of the largest gains in floor space of any extension, typically a big open-plan kitchen and living area below and two or more bedrooms or bathrooms above. In England it needs planning permission, because the side part is more than one storey.

Around Harrow on the Hill we also work in Harrow, Sudbury (Greater London) and Brent, and across the rest of Greater London. Postcode district in and near Harrow on the Hill: HA2.

What it costs in Harrow on the Hill

A guide price for Harrow on the Hill: around £144,500–£198,000 for an L-shaped footprint of about 28 m² wrapping the side and rear, on two floors (56 m² of new floor space). That works out at £2,580–£3,540 per m² of new floor space, including VAT at 20%. Design fees, structural calculations and approval fees are separate and listed on our prices page.

Spec	Per m²	An L-shaped footprint of about 28 m² wrapping the side and rear, on two floors (56 m² of new floor space)
Essential	£2,370–£3,260 per m²	£133,000–£182,500
Standard	£2,580–£3,540 per m²	£144,500–£198,000
Premium	£3,100–£4,250 per m²	£173,500–£238,000

Planning and building regulations in Harrow on the Hill

In England, a two-storey wraparound extension needs householder planning permission, because any extension beyond a side wall must be single storey to be permitted development. The application costs £548 (or £575 for applications made from 8 December 2026). Councils weigh the side part against the street scene and the rear part against neighbours' light and outlook, and should decide within 8 weeks of validation.

Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.

Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.

Design points for Harrow on the Hill homes

Phasing the build

A wraparound touches two sides of the house at once, so the kitchen and often the rear rooms are out of use for part of the build. We plan the sequence so you keep a working kitchen and bathroom for as long as possible, or advise when moving out briefly makes sense.

The corner post

At the outside corner of the L, there is no existing wall to carry the floor above. Opening the ground floor fully usually means a steel frame or a corner post, and the engineer's design sets how slim it can be. We decide early whether you want a clear corner or a visible post.

How we'd run your project

Measure and listen
A visit to Harrow on the Hill to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Get it approved
Once you're happy with the design we submit it to the council for Harrow on the Hill and deal with any questions from the planning officer.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Questions about two-storey wraparound extensions in Harrow on the Hill

How much does a two-storey wraparound extension cost in Harrow on the Hill?

Our guide for London, which covers Harrow on the Hill, is £2,580–£3,540 per m² including VAT. A typical project with an L-shaped footprint of about 28 m² wrapping the side and rear, on two floors (56 m² of new floor space) comes to about £144,500–£198,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Which postcodes do you cover around Harrow on the Hill?

We cover Harrow on the Hill (HA2) and nearby places including Harrow, Sudbury (Greater London) and Brent, plus the rest of Greater London. The first site visit is free.

How long does a two-storey wraparound extension take?

Allow 4 to 8 weeks for survey and design, then the approval period (councils should decide householder applications within 8 weeks of validation), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.

Does a wraparound extension need steel?

Almost always. Opening the corner of the house and the old rear wall to make one open-plan space means steel beams, and often a steel post or frame at the outside corner. The structural engineer sizes these, and the steel is ordered once the design is fixed, which is one reason a wraparound needs careful sequencing.

Is a wraparound extension better than separate side and rear extensions?

Building both at once usually costs less than two separate projects, because you pay for one set-up, one scaffold, one roof junction and one set of approvals. It also lets the layout be designed as a whole. The trade-off is a larger single outlay and a longer build, often 16 to 24 weeks at this size.

Nearby

The same service in neighbouring towns:

Other extensions in Harrow on the Hill

All two-storey extension services in Harrow on the Hill · Two-storey wraparound extensions across Greater London

Tell us about your house in Harrow on the Hill and we'll call you back to arrange a free, no-obligation visit.