What is a double-storey extension?
A double-storey extension (also called a two-storey extension) adds rooms on both the ground and first floor in one build. It typically gives a larger kitchen or living space downstairs and an extra bedroom or bathroom above.
How much does a double-storey extension cost in Grimsby?
In Grimsby, a double-storey extension typically costs £1,550–£2,400 per m² of floor area (both floors), including VAT at 20% (standard rate). For a typical 36 m² project that is roughly £56,000–£86,500. Prices across the East Midlands are typically 5% below the UK average for this kind of work, which is reflected in the range for Grimsby. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (25 m²) | £39,000–£60,000 |
| Typical project (36 m²) | £56,000–£86,500 |
| Larger project (50 m²) | £77,500–£120,000 |
| Rate per m² | £1,550–£2,400 |
The main things that change the cost:
- Bathrooms or en-suites on the first floor
- Brick matching and external finishes
- Roof design and how it joins the existing roof
- Steel beams where walls are opened up
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a double-storey extension in Grimsby?
Here is how the rules work for a double-storey extension in England. In England an extension of more than one storey can only be permitted development at the rear, no more than 3 metres deep and at least 7 metres from the rear boundary, with matching materials and any upper side windows obscure-glazed. Most double-storey extensions therefore go through a householder planning application.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
On a typical double-storey extension we handle:
- Brick or block walls, floors and a roof tied into the house
- Foundations, drainage and scaffolding
- Building control sign-off
- Opening up at both levels with steel beams
- Windows, doors and staircase alterations
- Structural engineer’s calculations
How long does it take?
Expect 14 to 20 weeks on site, after planning and building control approval. Design and approvals come first and typically take 3 to 4 months, depending on the approval route.
Building in Grimsby
In the East Midlands, many estates built since the 1960s have integral garages that convert well into a study or bedroom.
If your home is in Grimsby or close by in Cleethorpes, Hull and Brough, a free home visit is the first step.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about double-storey extensions in Grimsby
Who approves a double-storey extension in Grimsby?
Planning matters in Grimsby go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
Is a double-storey extension cheaper per square metre?
Usually yes. You pay for one set of foundations and one roof but get two floors of space, so the cost per square metre is often lower than a single-storey extension.
Can I live at home during the work?
Most families stay put. The shell is built first and the house is opened up late in the job, so disruption inside is limited to a few weeks.
How much does a double-storey extension cost in Grimsby?
In Grimsby, a double-storey extension typically costs £1,550–£2,400 per m² of floor area (both floors), including VAT at 20% (standard rate). A typical 36 m² project comes to roughly £56,000–£86,500. Your fixed price depends on the survey and drawings.
Will the first floor need a new staircase?
Not normally. The new rooms are reached from the existing landing, though a doorway or short corridor may need to be formed.