Double-storey extensions in Northfield

Double-storey extensions in Northfield: approvals and local details

Most two-storey extensions in Northfield need a planning application to Birmingham City Council. A two-storey rear extension can sometimes be permitted development, but only if it is no more than 3 m deep and at least 7 m from the rear boundary, among other conditions. Building Regulations approval is needed either way.

New first-floor bedrooms normally need an escape window with at least 0.33 m² of clear openable area.
Councils often expect a side extension's first floor to be set back from the front wall, with its roof below the main ridge.
The householder planning fee in England is £548 from April 2026, paid to Birmingham City Council when you apply.

Postcode district: B31
Planning and building control: Birmingham City Council
From our West Bromwich base: 7 miles

Which option fits your home?

Two-storey side extension

Built over the side of the house, often where a driveway or old garage sits. It can create a garage, utility or study downstairs with a double bedroom above. Councils often expect the upper floor to be set back from the front and the roof to sit lower than the main ridge, so the design needs care to win approval.

Mixed-height extension

A two-storey section at the side with a single-storey section running across the back. This keeps the first floor away from neighbours' windows while still giving a wide kitchen-diner below. It's a practical compromise where planners have concerns about a full-depth two-storey rear extension, and it often simplifies the roof.

How much should you budget in Northfield?

For a home in Northfield, our guide range is £52,000–£135,000 depending on size and specification. A two-storey side extension on a three-bed semi, about 32 m² over two floors: usually £68,000–£88,000.

Guide prices for double-storey extensions
Option	Guide price	Good to know
Compact two-storey rear (20–28 m² total)	£52,000 – £72,000	Bigger kitchen below, bedroom or bathroom above
Two-storey side or rear (30–40 m² total)	£68,000 – £98,000	The usual size on a three-bed semi
Large or combined side and rear (45 m²+)	£95,000 – £135,000	More steel, a complex roof and a longer programme

Guide ranges include VAT where it applies. Your fixed price for the agreed specification follows a free survey at your Northfield address.

Questions about double-storey extensions in Northfield

Can we stay in the house while you build?

Most families do. The early stages are outside, and the existing house stays closed off until the shell is weathertight. The harder weeks are when openings are cut through on both floors, which brings dust and noise into bedrooms and the kitchen. We sheet off openings, lock up securely every night and agree in advance which rooms you'll lose and when.

How do I book a survey in Northfield?

Send the form on this page, use the guide-price tool or call 0800 088 6248 free. We'll ask a few questions about your two-storey extension and arrange a time to visit.

What will the council look at when deciding planning?

Councils judge two-storey extensions mainly on their effect on neighbours and the street. They look at loss of light and outlook next door, overlooking from upstairs windows, and whether the extension sits comfortably with the house, often expecting side extensions to be set back and lower than the main roof. Many councils publish householder design guides, and following yours closely improves the chance of approval.

Will I need permission from the council in Northfield?

Usually both. Most two-storey extensions need a planning application to Birmingham City Council, and the structural work needs Building Regulations approval from its building control team or a registered building control approver.

Close to Northfield

Other home improvements in Northfield

Call 0800 088 6248 or send us your postcode, and we'll arrange a time to look at the house.