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 Durham?
In Durham, a double-storey extension typically costs £1,500–£2,250 per m² of floor area (both floors), including VAT at 20% (standard rate). For a typical 36 m² project that is roughly £54,000–£81,000. We start from a UK-wide guide and adjust it for the North East, where labour and materials are typically about 10% below average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (25 m²) | £37,500–£56,000 |
| Typical project (36 m²) | £54,000–£81,000 |
| Larger project (50 m²) | £75,000–£112,500 |
| Rate per m² | £1,500–£2,250 |
Your quote will depend mainly on:
- Roof design and how it joins the existing roof
- Brick matching and external finishes
- Bathrooms or en-suites on the first floor
- Total floor area across both floors
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 Durham?
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.
Where work involves a shared wall, building on the boundary, or digging foundations within 3 metres of a neighbour’s building and deeper than its foundations (or within 6 metres for deeper work), the Party Wall etc. Act 1996 applies and notices must be served before work starts.
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:
- Design drawings and planning application
- Opening up at both levels with steel beams
- Foundations, drainage and scaffolding
- Building control sign-off
- Brick or block walls, floors and a roof tied into the house
- Windows, doors and staircase alterations
How long does it take?
Build time is typically 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 Durham
Across the North East, colliery-era terraces and newer estates sit side by side, so the right project depends on the house type.
Projects in Durham (DH1) are surveyed in person before we quote, so the price reflects your actual property.
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 fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about double-storey extensions in Durham
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.
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 Durham?
Planning matters in Durham 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.
How much does a double-storey extension cost in Durham?
In Durham, a double-storey extension typically costs £1,500–£2,250 per m² of floor area (both floors), including VAT at 20% (standard rate). A typical 36 m² project comes to roughly £54,000–£81,000. Your fixed price depends on the survey and drawings.