Two-storey extensions for semi-detached houses in South Yorkshire

South Yorkshire at a glance

Nation: England
Price region: Yorkshire and the Humber
Postcode areas: DN, S
Towns covered: 28 listed below, plus surrounding villages
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.
Site visits: Free, no obligation

What a two-storey extension for a semi-detached house involves

A two-storey extension for a semi-detached house is a two-floor addition to the rear, the open side, or both, designed around the attached neighbour on one side. The rear is often the simplest option and can sometimes be permitted development, while a side extension uses the gap on the detached side. Both need care with the shared party wall and the neighbour's light.

South Yorkshire towns we list: Sheffield (S1), Rotherham (S60), Doncaster (DN1), Barnsley (S70), Bentley (DN5) and Burngreave (S4). Every other address in South Yorkshire is covered as well.

Guide price in Yorkshire and the Humber

In Yorkshire and the Humber, which includes South Yorkshire, we'd expect a two-storey extension for a semi-detached house to cost around £51,500–£69,500 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space), or £1,840–£2,480 per m² including VAT. Design fees, structural calculations and approval fees are separate and listed on our prices page.

Spec	Per m²	Typical project
Essential	£1,690–£2,290 per m²	£47,500–£64,000
Standard	£1,840–£2,480 per m²	£51,500–£69,500
Premium	£2,210–£2,980 per m²	£62,000–£83,500

Rules in England

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.

The Party Wall etc. Act 1996 applies, so notices may be needed for work on or near a shared wall or boundary.

Getting the design right

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 work in South Yorkshire

Visit and first ideas
One of our team visits your house in South Yorkshire, checks the walls, roof and drains, and sketches out options with you.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering South Yorkshire.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the building control completion certificate at the end.

Towns we cover in South Yorkshire

Two-storey extensions for semi-detached houses in South Yorkshire: questions

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

In Yorkshire and the Humber our guide is £1,840–£2,480 per m² including VAT, so about £51,500–£69,500 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Essential and Premium specs move that by roughly 8% down or 20% up.

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.

What if my neighbour has already extended?

That often helps. An existing extension next door can reduce the effect of yours on their light, and may show what the council accepts on your street. It can also mean building alongside their wall, so we check its position, foundations and any windows facing your plot at the survey.

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.

Will I need planning permission in South Yorkshire?

South Yorkshire is in England. 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.

Neighbouring areas

All extension services in South Yorkshire · About two-storey extensions for semi-detached houses