Cockfosters, Greater London
Rear extension planning drawings in Cockfosters
Measured survey, design options, planning drawings and the application, handled for you. We design, get the approvals for and build rear extensions in Cockfosters and the surrounding area, with one contract from the first survey to building control sign-off.
Cockfosters and its postcode districts EN4, N14 and N20 are part of our Greater London coverage. Rear extension applications in Greater London are householder applications, which councils aim to decide within about eight weeks.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
What do rear extension planning drawings cost in Cockfosters?
As a guide, £1,000–£2,500 including VAT for a single-storey rear extension, or £2,000–£3,500 for a two-storey scheme. A householder planning application in England costs £548 (£575 for applications made from 8 December 2026), and a lawful development certificate for proposed work costs half the householder fee. These are guide ranges; the written quote after the survey is the figure that counts.
Do you need planning permission for a rear extension in Cockfosters?
Whether your rear extension in Cockfosters needs a planning application depends on its size, your house and any local restrictions.
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.
Councils aim to decide householder applications within 8 weeks of validation, and prior approval within 42 days.
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 Cockfosters like to extend?
Much of Cockfosters is 1920s and 1930s semis and short terraces with longer gardens than inner London, which suit full-width single-storey rear extensions. Parking suspensions, skip licences and controlled hours on residential streets shape the programme more than the build itself.
How a rear extension in Cockfosters 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.
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.
Rear extension planning drawings near Cockfosters
From Cockfosters, the nearest places we also cover are East Barnet (0.6 miles) and New Barnet (1.2 miles).
- Rear extension planning drawings in East Barnet
- Rear extension planning drawings in New Barnet
- Rear extension planning drawings in Hadley Wood
- Rear extension planning drawings in Barnet
- Rear extension planning drawings in Totteridge
Other work in Cockfosters:
FAQ
Rear extension planning drawings questions in Cockfosters
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.
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.
Are the drawings mine?
You can use them to get other quotes, subject to the terms.
Can you match the brick or stone on my Cockfosters house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
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.
Do I need planning permission for a rear extension in Cockfosters?
Often not for a single-storey rear extension of up to 3 metres (4 metres on a detached house) under permitted development, or up to 6 or 8 metres with prior approval, unless the house is in a conservation area or its rights have been removed.