Part single, part two-storey extensions in Derbyshire

Derbyshire at a glance

Nation: England
Price region: East Midlands
Postcode areas: DE, NG, S, SK
Towns covered: 22 listed below, plus surrounding villages
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.
Site visits: Free, no obligation

What a part single, part two-storey extension involves

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.

Across Derbyshire we cover Derby (DE1), Chesterfield (S40), Long Eaton (DE72), Ilkeston (DE7), Swadlincote (DE11) and Staveley (S43), plus the smaller places around them.

Guide price in the East Midlands

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. Steelwork for wide openings is the item most likely to move the figure; we'll know once the engineer has designed it.

Spec	Per m²	Typical project
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

Rules in England

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.

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

Where to put the two-storey part

The two-storey section usually works best away from the closest neighbour, with the single-storey part on that boundary side. We test a few positions against neighbours' windows, the upstairs layout and the roof shape before choosing the one to take forward.

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 work in Derbyshire

Measure and listen
A visit to Derbyshire 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 Derbyshire and deal with any questions from the planning officer.
Structure and building control
A structural engineer sizes the foundations and steels, and we get building regulations approval before work starts.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Towns we cover in Derbyshire

Part single, part two-storey extensions in Derbyshire: questions

How much does a part single, part two-storey extension cost in Derbyshire?

In the East Midlands our guide is £1,960–£2,700 per m² including VAT, so about £70,500–£97,000 for a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total). Essential and Premium specs move that by roughly 8% down or 20% up.

Can the single-storey part be deeper than the two-storey part?

With planning permission, yes, and that is often the point of the design: the ground floor projects further into the garden while the first floor stays back from neighbours. Under permitted development, the depth limits for extensions of more than one storey can apply to the whole extension, so we confirm which route applies before drawings are finalised.

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.

Will I need planning permission in Derbyshire?

Derbyshire is in England. 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.

Neighbouring areas

All extension services in Derbyshire · About part single, part two-storey extensions