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 Gwent?
In Gwent, a double-storey extension typically costs £1,500–£2,300 per m² of floor area (both floors), including VAT at 20% (standard rate). For a typical 36 m² project that is roughly £54,000–£83,000. Building costs in Wales run about 8% below the UK average, and the figures for Gwent are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (25 m²) | £37,500–£57,500 |
| Typical project (36 m²) | £54,000–£83,000 |
| Larger project (50 m²) | £75,000–£115,000 |
| Rate per m² | £1,500–£2,300 |
Your quote will depend mainly on:
- Steel beams where walls are opened up
- Bathrooms or en-suites on the first floor
- Brick matching and external finishes
- Roof design and how it joins the existing roof
Use the guide price tool to see how size and specification change the figure, then ask for a written, itemised quote.
Do you need planning permission for a double-storey extension in Gwent?
Before anything is built in Gwent, we confirm which approvals apply in Wales. In Wales a rear extension of more than one storey can be permitted development if the ground floor projects no more than 4 metres and the upper floor no more than 3 metres, with at least 10.5 metres to the rear boundary and obscure-glazed upper side windows. It is not permitted development in conservation areas, National Parks or National Landscapes, so many double-storey extensions need a householder application.
The Party Wall etc. Act 1996 applies in Wales, so notices must be served before work on a shared wall, on the boundary, or excavation close to a neighbour’s foundations.
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:
- Design drawings and planning application
- Foundations, drainage and scaffolding
- Building control sign-off
- Electrics, heating, plumbing and plastering
- Structural engineer’s calculations
- Opening up at both levels with steel beams
How long does it take?
Allow 14 to 20 weeks on site, after planning and building control approval. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Gwent
Wales has many terraced valley streets, stone cottages and post-war estates, so extension designs are shaped by slopes, materials and local character.
Towns we cover in Gwent include Newport, Cwmbran, Pontypool, Ebbw Vale, Risca and Abergavenny.
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 in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about double-storey extensions in Gwent
Do you build double-storey extensions in Gwent?
Yes. We build double-storey extensions across Gwent, including postcodes CF3, CF83, NP10, NP19 and NP20. Every project starts with a free home visit.
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.
How much does a double-storey extension cost in Gwent?
In Gwent, a double-storey extension typically costs £1,500–£2,300 per m² of floor area (both floors), including VAT at 20% (standard rate). A typical 36 m² project comes to roughly £54,000–£83,000. Your fixed price depends on the survey and drawings.
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.
Do I need planning permission for a double-storey extension in Gwent?
In Wales a rear extension of more than one storey can be permitted development if the ground floor projects no more than 4 metres and the upper floor no more than 3 metres, with at least 10.5 metres to the rear boundary and obscure-glazed upper side windows. It is not permitted development in conservation areas, National Parks or National Landscapes, so many double-storey extensions need a householder application.