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 Crouch End?
In Crouch End, a double-storey extension typically costs £2,150–£3,250 per m² of floor area (both floors), including VAT at 20% (standard rate). For a typical 36 m² project that is roughly £77,500–£117,000. That range is adjusted for London, where domestic building work typically costs around 30% above the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (25 m²) | £54,000–£81,000 |
| Typical project (36 m²) | £77,500–£117,000 |
| Larger project (50 m²) | £107,500–£162,500 |
| Rate per m² | £2,150–£3,250 |
The main things that change the cost:
- Roof design and how it joins the existing roof
- Bathrooms or en-suites on the first floor
- Scaffolding and access to the rear
- Steel beams where walls are opened up
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a double-storey extension in Crouch End?
The approval route for Crouch End is set by planning law 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.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
The work we manage on a double-storey extension:
- Brick or block walls, floors and a roof tied into the house
- Windows, doors and staircase alterations
- Building control sign-off
- Structural engineer’s calculations
- Design drawings and planning application
- Electrics, heating, plumbing and plastering
How long does it take?
Expect 14 to 20 weeks on site, after planning and building control approval. Before that, surveys, drawings and approvals usually take 3 to 4 months, longer if the council asks for changes.
Building in Crouch End
Space is at a premium in London, so homeowners often build out into the side return or up into the roof rather than move.
Our Crouch End coverage includes postcode districts N8, and we also work in nearby places such as Muswell Hill, Wood Green and Highgate.
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 Crouch End
How much does a double-storey extension cost in Crouch End?
In Crouch End, a double-storey extension typically costs £2,150–£3,250 per m² of floor area (both floors), including VAT at 20% (standard rate). A typical 36 m² project comes to roughly £77,500–£117,000. Your fixed price depends on the survey and drawings.
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 close can it be to my neighbour?
Councils look at loss of light and outlook for neighbours. Many apply a 45-degree guideline from the nearest neighbouring window. We design to the council’s published guidance to give the application the best chance.
Do you build double-storey extensions in Crouch End?
Yes. We build double-storey extensions across Crouch End, including postcodes N8. Every project starts with a free home visit.
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.