Two-storey rear extensions in Grimsby

Quick reference for homeowners in Grimsby.

Postcode districts: DN31, DN32, DN33, DN34 and DN37
County / area: Lincolnshire, England
Price region: East Midlands
Guide price: £55,000–£74,000 (£1,960–£2,650 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 two-storey rear extension

A two-storey rear extension is a new two-floor addition built onto the back of your house, usually giving a larger kitchen or living space on the ground floor and one or two bedrooms or a bathroom above. Because both floors share one set of foundations and one roof, it adds a lot of floor space for the garden it uses. In some cases it can be built under permitted development, depending on where you live.

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

Using our East Midlands rates, a two-storey rear extension with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £55,000–£74,000, including VAT. Bigger or more glazed designs cost more per m². Keep a contingency of around 10% for things nobody can see until the ground is opened up.

Spec	Per m²	A 4 m × 3.5 m footprint on two floors (28 m² of new floor space)
Essential	£1,800–£2,430 per m²	£50,500–£68,000
Standard	£1,960–£2,650 per m²	£55,000–£74,000
Premium	£2,350–£3,180 per m²	£66,000–£89,000

Planning and building regulations in Grimsby

In England, a two-storey rear extension can be permitted development if it goes no more than 3 m beyond the rear wall of the original house, stays at least 7 m from the rear boundary and matches the house's materials and roof pitch. It is not permitted development in conservation areas, National Landscapes, National Parks, World Heritage Sites or the Broads. Otherwise a householder application costs £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

Foundations and drains

Foundations for two storeys carry more load than a single storey and may need to go deeper near trees or on clay. Rear extensions often sit near drains, so we check sewer records early, as building over or near a public sewer may need the water company's agreement.

Upstairs layout and windows

Bedrooms above need a window big enough for escape or a protected route to the stairs. Side-facing upstairs windows normally have to be obscure-glazed and fixed below 1.7 m, so we put the main bedroom windows in the rear wall and use roof lights where extra daylight is needed.

How we'd run your project

Free site visit
We visit your home in Grimsby, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
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 it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.

Questions about two-storey rear extensions in Grimsby

Which postcodes do you cover around Grimsby?

We cover Grimsby (DN31, DN32, DN33, DN34 and DN37) and nearby places including Cleethorpes, Immingham and Hedon, plus the rest of Lincolnshire. The first site visit is free.

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 two-storey rear 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.

Will a two-storey rear extension block my neighbour's light?

It can if it is too deep or too close to the boundary, which is why councils look closely at its effect on neighbouring windows and gardens. We test the design against light and outlook early, keep the first floor shorter or set in where needed, and use a hipped roof to reduce bulk on the boundary side.

Can I have a balcony on a two-storey rear extension?

In England, balconies, verandas and raised platforms are not permitted development, so a balcony on a two-storey rear extension needs planning permission. A Juliet balcony, a guard rail across full-height doors with no platform to stand on, is often a practical alternative, but it still needs checking against the rules and the council's approach to overlooking.

Nearby

Nearby towns we cover for two-storey rear extensions:

Other extensions in Grimsby

All two-storey extension services in Grimsby · Two-storey rear extensions across Lincolnshire

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