Two-storey extensions for semi-detached houses in Failsworth

Failsworth: the key facts for this kind of project.

Postcode districts: M35 and M40
County / area: Greater Manchester, England
Price region: North West England
Guide price: £53,000–£72,000 (£1,900–£2,560 per m²)
Approval route: Depends on position: a two-storey rear extension may be permitted development (3 m deep, 7 m from the rear boundary); a two-storey side extension needs planning permission.
Nearest towns: Hollinwood (1.6 miles), Droylsden (1.9 miles), Blackley (2.2 miles)
Distance to Manchester: about 3.4 miles
First visit: Free, no obligation

About a two-storey extension for a semi-detached house

This service suits you if you own a semi-detached house and want to add bedrooms and living space without moving. On a semi, the main questions are which side to build on and how to treat the attached neighbour. You get a survey, design options, the approvals your nation needs and the build, carried out by vetted teams working under S&K.

We cover Failsworth (M35 and M40) and the places around it, including Hollinwood (1.6 miles), Droylsden (1.9 miles) and Blackley.

What it costs in Failsworth

Expect a two-storey extension for a semi-detached house in Failsworth to land somewhere around £53,000–£72,000 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Our North West England guide rate is £1,900–£2,560 per m², including VAT. Design fees, structural calculations and approval fees are separate and listed on our prices page.

Spec	Per m²	A 4 m × 3.5 m footprint on two floors (28 m² of new floor space)
Essential	£1,750–£2,360 per m²	£49,000–£66,000
Standard	£1,900–£2,560 per m²	£53,000–£72,000
Premium	£2,280–£3,080 per m²	£64,000–£86,000

Planning and building regulations in Failsworth

In England, a two-storey rear extension on a semi can be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary, with matching materials and roof pitch. A two-storey side or wraparound extension always needs planning permission, costing £548 (or £575 for applications made from 8 December 2026). Protected areas such as conservation areas exclude two-storey rear permitted development.

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 Failsworth homes

Rear, side or both

On a semi, a rear extension sits against the attached neighbour, while a side extension faces the detached neighbour and the street. We compare the space, cost and approval route for each, and for a wraparound, before you commit to one design.

Keeping the pair balanced

Semis are designed as matching pairs, and a side extension changes that balance. Setting the side extension back from the front wall and keeping its ridge lower helps the pair still read as a pair, which councils' design guides commonly ask for.

How we'd run your project

Visit and first ideas
One of our team visits your house in Failsworth, checks the walls, roof and drains, and sketches out options with you.
Design and approvals
We draw the extension and check it against the rules for England, then apply for planning permission or a certificate of lawfulness, whichever fits.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Build it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.

Questions about two-storey extensions for semi-detached houses in Failsworth

Which postcodes do you cover around Failsworth?

We cover Failsworth (M35 and M40) and nearby places including Hollinwood, Droylsden and Blackley, plus the rest of Greater Manchester. The first site visit is free.

How long does a two-storey extension for a semi-detached house 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.

How much does a two-storey extension for a semi-detached house cost in Failsworth?

Our guide for North West England, which covers Failsworth, is £1,900–£2,560 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £53,000–£72,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Will a side extension make my semi look like a terrace?

It can if it fills the whole gap to the boundary at first floor and the neighbour does the same. Many councils ask for a first-floor gap to the side boundary or a set-back for this reason. We design the extension to keep the semi reading as one of a pair.

Should I extend my semi to the side or the rear?

It depends on your plot and what you need. A rear extension keeps the side drive and can sometimes be permitted development, but it affects the attached neighbour. A side extension keeps the rear garden but always needs planning permission in England. We compare both at the free site visit.

Nearby

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The quickest next step is a visit. We'll look at your house in Failsworth and give you an honest view of the options.