Rear extension design, approvals and build across the UKCall 0800 088 6341 · Online guide price
Rear Extensionsrear-extensions.co.uk 0800 088 6341 Get a guide price

Northumberland Park, Greater London

Semi-detached rear extension in Northumberland Park

Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Northumberland Park 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.

Northumberland Park and its postcode districts N9, N17 and N18 are part of our Greater London coverage. Where a Northumberland Park 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 Northumberland Park?

A semi-detached rear extension in Northumberland Park is priced at £2,470–£4,030 per square metre including VAT as a guide, before kitchen fit-out and fees. London prices sit at the top of our range because of labour rates, access through the house, parking suspensions and skip licences.

Semi-detached rear extension prices in Northumberland Park
SizeGuide 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

We put a fixed price in writing once the design is agreed, and explain any provisional sums such as foundations.

Do you need planning permission for a semi-detached rear extension in Northumberland Park?

Planning for a semi-detached rear extension in Northumberland Park 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.

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. 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 Northumberland Park like to extend?

Much of Northumberland Park is Victorian and Edwardian terraced housing with narrow back additions, which suits side returns, wraparounds and 3 metre rear extensions. Many streets are in conservation areas, gardens are short, and almost everything comes through the house or along a rear alley.

How a semi-detached rear extension in Northumberland Park comes together

  1. 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.

  2. Options and costs

    We draw layout options and price each one, so the budget shapes the design rather than surprising you later.

  3. Planning and regulations

    We take the design through the right planning route, then produce the construction drawings and engineer's calculations for building control.

  4. 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.

Semi-detached rear extensions near Northumberland Park

We also build rear extensions for semi-detached houses in nearby Tottenham (0.4 miles) and Tottenham Hale (0.7 miles).

Other work in Northumberland Park:

All rear extensions in Northumberland Park

FAQ

Semi-detached rear extension questions in Northumberland Park

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.

How long does a rear extension take to build in Northumberland Park?

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 match pebbledash or render?

Yes. Many semis are refinished with new render across the whole back elevation so old and new match.

Can you match the brick or stone on my Northumberland Park house?

We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.

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.

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.

Next step

See what your rear extension would cost

Get a guide price online in a couple of minutes, or book a free site visit and we'll measure up and talk you through the planning route.

CallGuide price