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 Retford?
In Retford, 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 Retford. 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 |
What moves the price most:
- Roof design and how it joins the existing roof
- Total floor area across both floors
- Bathrooms or en-suites on the first floor
- Scaffolding and access to the rear
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 Retford?
Whether you need planning permission depends on your house and its location 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.
We check this for your address before design work starts, so there are no surprises later.
What we handle
Handled as part of most double-storey extensions:
- Brick or block walls, floors and a roof tied into the house
- Opening up at both levels with steel beams
- Building control sign-off
- Design drawings and planning application
- Foundations, drainage and scaffolding
- Windows, doors and staircase alterations
How long does it take?
Allow 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 Retford
The East Midlands has a mix of red-brick terraces, inter-war semis and newer estates, so rear extensions and garage conversions are common projects.
Projects in Retford (DN22) are surveyed in person before we quote, so the price reflects your actual property.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about double-storey extensions in Retford
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.
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.
What drawings do I need?
Planning drawings for the application, then more detailed building regulations drawings and structural calculations for building control. We prepare both.
How much does a double-storey extension cost in Retford?
In Retford, 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.
Who approves a double-storey extension in Retford?
Planning matters in Retford go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.