First-floor extensions in Blackley

Quick reference for homeowners in Blackley.

Postcode districts: M9
County / area: Greater Manchester, England
Price region: North West England
Guide price: £24,000–£34,500 (£1,710–£2,470 per m²)
Approval route: It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission.
Nearest towns: Crumpsall (1.2 miles), Cheetham Hill (1.6 miles), Failsworth (2.2 miles)
Distance to Manchester: about 2.7 miles
First visit: Free, no obligation

About a first-floor extension

A first-floor extension is a new upstairs room built on top of an existing single-storey part of your house, such as a rear kitchen extension, a utility or a side annexe. It adds a bedroom, bathroom or study without enlarging the footprint. Whether it works depends mainly on whether the walls and foundations below can carry the extra load.

We cover postcode district M9 in and around Blackley, along with neighbouring Crumpsall, Cheetham Hill and Failsworth.

What it costs in Blackley

A guide price for Blackley: around £24,000–£34,500 for 4 m × 3.5 m of new first-floor space (14 m²). That works out at £1,710–£2,470 per m² of new floor space, including VAT at 20%. We'll give you a written design-stage price first, then a fixed build price once the drawings are agreed.

Spec	Per m²	4 m × 3.5 m of new first-floor space (14 m²)
Essential	£1,570–£2,270 per m²	£22,000–£32,000
Standard	£1,710–£2,470 per m²	£24,000–£34,500
Premium	£2,050–£2,960 per m²	£28,500–£41,500

Planning and building regulations in Blackley

In England, adding a first floor turns a single-storey extension into one of more than one storey. To be permitted development, the extension as a whole must go no more than 3 m beyond the rear wall of the original house and stay at least 7 m from the rear boundary, with matching materials and roof pitch. Over a side extension it always needs planning permission, costing £548 (or £575 for applications made from 8 December 2026).

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 Blackley homes

Matching the roofline

A first-floor extension often changes how the back or side of the house looks more than the original single storey did. Matching the main roof pitch and materials, and keeping the ridge below the main ridge, usually gives the best result and is expected for permitted development in England.

Escape and fire safety

A new first-floor bedroom needs an escape window with a clear opening of at least 0.33 m², at least 450 mm wide and 450 mm high, with the bottom no more than 1,100 mm above the floor, unless there is a protected route to the stairs.

How we'd run your project

Start at your house
We come to your home in Blackley, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Structure and building control
A structural engineer sizes the foundations and steels, and we get building regulations approval before work starts.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.

Questions about first-floor extensions in Blackley

Which postcodes do you cover around Blackley?

We cover Blackley (M9) and nearby places including Crumpsall, Cheetham Hill and Failsworth, plus the rest of Greater Manchester. The first site visit is free.

How much does a first-floor extension cost in Blackley?

Our guide for North West England, which covers Blackley, is £1,710–£2,470 per m² including VAT. A typical project with 4 m × 3.5 m of new first-floor space (14 m²) comes to about £24,000–£34,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Do I need planning permission for a first-floor extension in Blackley?

Blackley is in England, so England planning rules apply. It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.

Will the first-floor extension match my house?

It should, and in England matching materials and roof pitch is a condition of permitted development. We match brick, tile, mortar colour and window style where we can, and tell you at the design stage if an exact brick match is not available, so you can choose between the closest match and render or cladding.

What happens to the room below while the first floor is built?

The old roof is removed, so the room below is exposed for a short period. We fit temporary weather protection, plan the work so the roof comes off only when the new structure is ready, and agree with you which rooms will be out of use and for roughly how long.

Nearby

Close to Blackley? We work across the area, including:

Other extensions in Blackley

All two-storey extension services in Blackley · First-floor extensions across Greater Manchester

Book a free site visit in Blackley and we'll tell you what's possible, what approvals you need and what the design stage would cost.