Part single, part two-storey extensions in Mountsorrel

Useful details for planning a part single, part two-storey extension in Mountsorrel.

Postcode districts: LE4
County / area: Leicestershire, England
Price region: East Midlands
Guide price: £70,500–£97,000 (£1,960–£2,700 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: Birstall (3.7 miles), Loughborough (4 miles), Syston (4.2 miles)
Distance to Leicester: about 5.5 miles
First visit: Free, no obligation

About a part single, part two-storey extension

A part single, part two-storey extension suits you if you want a generous ground floor but only need one extra room upstairs, or if a full two-storey design would affect a neighbour too much. You get design options that test where the two-storey part works best, the approvals your nation needs, structural design, building regulations approval and the build, carried out by vetted teams working under S&K.

We cover postcode district LE4 in and around Mountsorrel, along with neighbouring Birstall, Loughborough and Syston.

What it costs in Mountsorrel

Guide prices for part single, part two-storey extensions in the East Midlands are around £1,960–£2,700 per m² of new floor space, including VAT. For a typical project with a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total), that's roughly £70,500–£97,000. Professional fees for drawings and the structural engineer are listed separately on our prices page.

Spec	Per m²	A 6 m × 4 m ground floor and a first floor over half of it (36 m² in total)
Essential	£1,800–£2,480 per m²	£65,000–£89,500
Standard	£1,960–£2,700 per m²	£70,500–£97,000
Premium	£2,350–£3,230 per m²	£84,500–£116,500

Planning and building regulations in Mountsorrel

In England, the extension can only be permitted development if it goes no more than 3 m beyond the original rear wall and stays at least 7 m from the rear boundary, with matching materials and roof pitch. We check the whole design against the rules, including the 50% garden coverage limit. If any part fails, or extends beyond a side wall on two floors, you need 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 Mountsorrel homes

Structure at the step

The first-floor wall above often sits over the new open-plan space, so it needs a steel beam or frame to carry it. Loads come down at different points than in a full two-storey design, and the engineer sizes the foundations to suit each part.

Light into the kitchen

The single-storey part is the place for roof lights or a lantern, which bring daylight deep into the plan. In England, glazing is normally limited to 25% of the new floor area plus any windows removed, unless calculations show the house still performs, so we plan the balance early.

How we'd run your project

Measure and listen
A visit to Mountsorrel to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Get it approved
Once you're happy with the design we submit it to the council for Mountsorrel and deal with any questions from the planning officer.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.

Questions about part single, part two-storey extensions in Mountsorrel

Which postcodes do you cover around Mountsorrel?

We cover Mountsorrel (LE4) and nearby places including Birstall, Loughborough and Syston, plus the rest of Leicestershire. The first site visit is free.

Do I need planning permission for a part single, part two-storey extension in Mountsorrel?

Mountsorrel 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.

How long does a part single, part two-storey extension 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.

Which side should the two-storey part go on?

Usually the side furthest from the nearest neighbour's windows, so the single-storey part sits nearest them and keeps their light. Other factors are where the stairs land upstairs, which room needs the extra space and where drains run. We sketch options at the design stage and explain which is most likely to be approved.

Can I add roof lights to the single-storey part?

Yes. Roof lights or a lantern over the single-storey part are one of the main reasons to choose this design, as they light the middle of a deep kitchen. In England they count towards the Part L glazing allowance, normally 25% of the new floor area plus windows removed, so we balance them with the rear doors.

Nearby

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