Part single, part two-storey extensions in Grimsby

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

Postcode districts: DN31, DN32, DN33, DN34 and DN37
County / area: Lincolnshire, 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: Cleethorpes (1.8 miles), Immingham (6.7 miles), Hedon (13 miles)
Distance to Lincoln: about 30.2 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.

Grimsby sits about 30.2 miles from Lincoln. Closer to home, Cleethorpes is 1.8 miles away and Immingham 6.7 miles.

What it costs in Grimsby

Most of the cost of a part single, part two-storey extension is set by its size and specification. For Grimsby and the rest of 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). These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.

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 Grimsby

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 Grimsby 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.

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.

How we'd run your project

Start at your house
We come to your home in Grimsby, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Get it approved
Once you're happy with the design we submit it to the council for Grimsby 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.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the building control completion certificate at the end.

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

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

Our guide for the East Midlands, which covers Grimsby, is £1,960–£2,700 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 £70,500–£97,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Who handles building regulations for a project in Grimsby?

We handle it as part of the project. What's needed in England: building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.

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

Grimsby 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.

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

Nearby towns we cover for part single, part two-storey extensions:

Other extensions in Grimsby

All two-storey extension services in Grimsby · Part single, part two-storey extensions across Lincolnshire

Tell us about your house in Grimsby and we'll call you back to arrange a free, no-obligation visit.