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 Redruth?
In Redruth, a double-storey extension typically costs £1,700–£2,550 per m² of floor area (both floors), including VAT at 20% (standard rate). For a typical 36 m² project that is roughly £61,000–£92,000. Building costs in the South West are close to the UK average, so the figures for Redruth are close to our national guide. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (25 m²) | £42,500–£64,000 |
| Typical project (36 m²) | £61,000–£92,000 |
| Larger project (50 m²) | £85,000–£127,500 |
| Rate per m² | £1,700–£2,550 |
What moves the price most:
- Steel beams where walls are opened up
- Total floor area across both floors
- Roof design and how it joins the existing roof
- Scaffolding and access to the rear
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a double-storey extension in Redruth?
Before anything is built in Redruth, we confirm which approvals apply 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.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
Handled as part of most double-storey extensions:
- Electrics, heating, plumbing and plastering
- Windows, doors and staircase alterations
- Opening up at both levels with steel beams
- Structural engineer’s calculations
- Foundations, drainage and scaffolding
- Design drawings and planning application
How long does it take?
The build itself usually takes 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 Redruth
The South West mixes stone and render cottages with post-war and newer estates, and local materials matter more here when matching an extension.
Redruth sits in Cornwall, about 8 miles west of Truro. We cover the whole of Redruth, including postcodes TR15.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about double-storey extensions in Redruth
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.
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.
Who approves a double-storey extension in Redruth?
Planning matters in Redruth go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
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 Redruth?
In Redruth, a double-storey extension typically costs £1,700–£2,550 per m² of floor area (both floors), including VAT at 20% (standard rate). A typical 36 m² project comes to roughly £61,000–£92,000. Your fixed price depends on the survey and drawings.