Part single, part two-storey extensions in Blyth

Quick reference for homeowners in Blyth.

Postcode districts: NE24
County / area: Northumberland, England
Price region: North East England
Guide price: £65,000–£89,000 (£1,800–£2,480 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: Cowpen (1.3 miles), Bedlington (3.4 miles), Stakeford (3.5 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 NE24 in and around Blyth, along with neighbouring Cowpen, Bedlington and Stakeford.

What it costs in Blyth

Expect a part single, part two-storey extension in Blyth to land somewhere around £65,000–£89,000 for a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total). Our North East England guide rate is £1,800–£2,480 per m², including VAT. The fastest way to a firmer number is a free site visit, after which we price the design stage in writing.

Spec	Per m²	A 6 m × 4 m ground floor and a first floor over half of it (36 m² in total)
Essential	£1,660–£2,280 per m²	£59,500–£82,000
Standard	£1,800–£2,480 per m²	£65,000–£89,000
Premium	£2,160–£2,970 per m²	£78,000–£107,000

Planning and building regulations in Blyth

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 Blyth homes

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.

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

Understand the brief
At your home in Blyth we agree what you need: bedroom count, bathroom, kitchen space, and how much garden you want to keep.
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.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.

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

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

Our guide for North East England, which covers Blyth, is £1,800–£2,480 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 £65,000–£89,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

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

Blyth 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.

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.

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

Close to Blyth? We work across the area, including:

Other extensions in Blyth

All two-storey extension services in Blyth · Part single, part two-storey extensions across Northumberland

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