First-floor extensions in Runcorn
Our first-floor extensions service in Runcorn covers everything: measured survey, design, planning or permitted development checks, structural design, building control and the build itself.
Useful details for planning a first-floor extension in Runcorn.
- Postcode districts
- WA6 and WA7
- County / area
- Cheshire, England
- Price region
- North West England
- Guide price
- £24,000–£34,500 (£1,710–£2,470 per m²)
- Approval route
- It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission.
- Nearest towns
- Widnes (1.4 miles), Halewood (4.3 miles), Speke (4.5 miles)
- Distance to Warrington
- about 7.1 miles
- First visit
- Free, no obligation
About a first-floor extension
A first-floor extension is a new upstairs room built on top of an existing single-storey part of your house, such as a rear kitchen extension, a utility or a side annexe. It adds a bedroom, bathroom or study without enlarging the footprint. Whether it works depends mainly on whether the walls and foundations below can carry the extra load.
We cover Runcorn (WA6 and WA7) and the places around it, including Widnes (1.4 miles), Halewood (4.3 miles) and Speke.
What it costs in Runcorn
Our guide for North West England is £1,710–£2,470 per m² including VAT. On a project with 4 m × 3.5 m of new first-floor space (14 m²), that puts a first-floor extension in Runcorn at roughly £24,000–£34,500. We'll give you a written design-stage price first, then a fixed build price once the drawings are agreed.
| Spec | Per m² | 4 m × 3.5 m of new first-floor space (14 m²) |
|---|---|---|
| Essential | £1,570–£2,270 per m² | £22,000–£32,000 |
| Standard | £1,710–£2,470 per m² | £24,000–£34,500 |
| Premium | £2,050–£2,960 per m² | £28,500–£41,500 |
Planning and building regulations in Runcorn
In England, adding a first floor turns a single-storey extension into one of more than one storey. To be permitted development, the extension as a whole must go no more than 3 m beyond the rear wall of the original house and stay at least 7 m from the rear boundary, with matching materials and roof pitch. Over a side extension it always needs planning permission, costing £548 (or £575 for applications made from 8 December 2026).
Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.
Design points for Runcorn homes
Tying into the house
The new floor and walls must line up with the existing first floor, often through a new opening in the rear wall above the old one. Floor levels, the position of upstairs windows and the existing roof all affect where the opening can go, so we survey both floors carefully.
Escape and fire safety
A new first-floor bedroom needs an escape window with a clear opening of at least 0.33 m², at least 450 mm wide and 450 mm high, with the bottom no more than 1,100 mm above the floor, unless there is a protected route to the stairs.
How we'd run your project
Start at your house
We come to your home in Runcorn, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.
Questions about first-floor extensions in Runcorn
Who handles building regulations for a project in Runcorn?
We handle it as part of the project. What's needed in England: building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.
How much does a first-floor extension cost in Runcorn?
Our guide for North West England, which covers Runcorn, is £1,710–£2,470 per m² including VAT. A typical project with 4 m × 3.5 m of new first-floor space (14 m²) comes to about £24,000–£34,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Which postcodes do you cover around Runcorn?
We cover Runcorn (WA6 and WA7) and nearby places including Widnes, Halewood and Speke, plus the rest of Cheshire. The first site visit is free.
What happens to the room below while the first floor is built?
The old roof is removed, so the room below is exposed for a short period. We fit temporary weather protection, plan the work so the roof comes off only when the new structure is ready, and agree with you which rooms will be out of use and for roughly how long.
Can I build on top of my existing single-storey extension?
Often yes, but only after the structure has been checked. Foundations, walls and lintels built for one storey may not carry two. We dig trial holes, look for the original building control approval and ask the structural engineer to confirm what can stay, what needs strengthening and what must be rebuilt.
Nearby
Nearby towns we cover for first-floor extensions:
Other extensions in Runcorn
- Rear
- Side
- Wraparound
- Part two-storey
- Over a garage
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Runcorn · First-floor extensions across Cheshire
Book a free site visit in Runcorn and we'll tell you what's possible, what approvals you need and what the design stage would cost.