Two-storey extensions for semi-detached houses in Mexborough

Before you start in Mexborough, here's what applies.

Postcode districts: S64
County / area: South Yorkshire, England
Price region: Yorkshire and the Humber
Guide price: £51,500–£69,500 (£1,840–£2,480 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: Bolton-upon-Dearne (1.9 miles), Wath-upon-Dearne (2.3 miles), Conisbrough (2.6 miles)
Distance to Sheffield: about 10.5 miles
First visit: Free, no obligation

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

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.

Around Mexborough we also work in Bolton-upon-Dearne, Wath-upon-Dearne and Conisbrough, and across the rest of South Yorkshire. Postcode district in and near Mexborough: S64.

What it costs in Mexborough

Guide prices for two-storey extensions for semi-detached houses in Yorkshire and the Humber are around £1,840–£2,480 per m² of new floor space, including VAT. For a typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space), that's roughly £51,500–£69,500. 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	£1,690–£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

Planning and building regulations in Mexborough

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 Mexborough 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.

The attached neighbour's light

A two-storey rear extension next to the party wall can take light from the neighbour's rear windows. Councils often use a 45-degree test, so the first floor may need to be shorter than the ground floor or set in from the shared boundary.

How we'd run your project

Start at your house
We come to your home in Mexborough, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
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 and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

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

Do I need planning permission for a two-storey extension for a semi-detached house in Mexborough?

Mexborough is in England, so England planning rules apply. 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. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.

Which postcodes do you cover around Mexborough?

We cover Mexborough (S64) and nearby places including Bolton-upon-Dearne, Wath-upon-Dearne and Conisbrough, plus the rest of South Yorkshire. The first site visit is free.

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

Our guide for Yorkshire and the Humber, which covers Mexborough, is £1,840–£2,480 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 £51,500–£69,500. 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.

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.

Nearby

The same service in neighbouring towns:

Other extensions in Mexborough

All two-storey extension services in Mexborough · Two-storey extensions for semi-detached houses across South Yorkshire

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