Part single, part two-storey extensions in Colne

The basics for Colne at a glance.

Postcode districts: BB8
County / area: Lancashire, England
Price region: North West England
Guide price: £68,500–£94,000 (£1,900–£2,610 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: Nelson (Lancashire) (2.1 miles), Brierfield (3.5 miles), Barnoldswick (4.2 miles)
Distance to Preston: about 22.8 miles
First visit: Free, no obligation

About a part single, part two-storey extension

A part single, part two-storey extension is an extension where the ground floor is wider or deeper than the floor above, so only part of it rises to two storeys. It usually gives a large kitchen or living area with roof lights below and one bedroom or bathroom above. It is often a good way to add space while limiting the effect on neighbours.

Around Colne we also work in Nelson (Lancashire), Brierfield and Barnoldswick, and across the rest of Lancashire. Postcode district in and near Colne: BB8.

What it costs in Colne

Using our North West England rates, a part single, part two-storey extension with a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total) comes to about £68,500–£94,000, including VAT. Bigger or more glazed designs cost more per m². Design fees, structural calculations and approval fees are separate and listed 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	£1,750–£2,400 per m²	£63,000–£86,500
Standard	£1,900–£2,610 per m²	£68,500–£94,000
Premium	£2,280–£3,130 per m²	£82,000–£113,000

Planning and building regulations in Colne

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 Colne homes

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.

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.

How we'd run your project

Visit and first ideas
One of our team visits your house in Colne, checks the walls, roof and drains, and sketches out options with you.
Plans, then approval
Measured survey, design, then the right approval route for your house. We explain each step before we take it.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

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

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

Our guide for North West England, which covers Colne, is £1,900–£2,610 per m² including VAT. A typical project with a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total) comes to about £68,500–£94,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Which postcodes do you cover around Colne?

We cover Colne (BB8) and nearby places including Nelson (Lancashire), Brierfield and Barnoldswick, plus the rest of Lancashire. The first site visit is free.

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.

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.

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.

Nearby

We also cover places near Colne, including:

Other extensions in Colne

All two-storey extension services in Colne · Part single, part two-storey extensions across Lancashire

Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.