Local costs · Wales · September 2026
How much does an extension cost in Conwy?
A mid-range 25 m² single-storey extension in Conwy costs about £57,000 to £70,000 including VAT, or £2,300 to £2,800 per m² at Welsh prices. Conwy’s own published charge for building control on a 10 to 40 m² extension is £648 (full plans, including VAT): the 5th cheapest of the 91 councils we checked, 23% below the typical council (£840). With a measured survey, building regulations drawings, a structural engineer, Conwy’s own building control charge and a 15% contingency, plan for £69,500 to £88,500.
Work out your project in Conwy
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Typical prices in Conwy
| Project | Building work | Budget to plan for |
|---|---|---|
| Single-storey extension, 25 m² | £57,000 to £70,000 | £69,500 to £88,500 |
| Double-storey extension, 40 m² | £82,000 to £104,000 | £99,000 to £129,000 |
| Dormer loft conversion, 30 m² | £42,500 to £52,000 | £52,000 to £67,500 |
| Kitchen, medium | £8,600 to £15,200 | £9,800 to £17,500 |
| Bathroom refit | £5,600 to £8,500 | £6,500 to £9,700 |
Building prices in Wales run about 10% below the UK average outside London. Kitchens and bathrooms vary less from place to place than extensions and lofts.
Building control fees in Conwy
| Work | Charge |
|---|---|
| Extension up to 10 m² (full plans) | £465.60 |
| Extension 10 to 40 m² (full plans) | £648 |
| Larger extension, 40 to 60 m² (full plans) | £715.20 |
| Extension 10 to 40 m² (building notice) | £648 |
| Loft conversion up to 40 m² | £648 |
| Garage conversion | Not published |
Conwy’s own published charge for building control on a 10 to 40 m² extension is £648 (full plans, including VAT): the 5th cheapest of the 91 councils we checked, 23% below the typical council (£840). Source: Conwy’s building control charges. Schedule date: 2026-27. Conwy publishes its charges without VAT, so we added VAT at 20%.
Private building control firms (registered building control approvers) set their own prices and are often competitive, so it is worth asking one or two for a quote as well. See how Conwy compares with every council we checked.
Notes on Conwy’s schedule
Conwy publishes its own schedule in its application form for 2026 to 2027. It has no separate charge for a garage conversion, and the loft figure is for up to 50 m².
Planning
If your extension needs planning permission, a householder application in Wales costs £585. Many single-storey rear extensions are permitted development and need no application, and a lawful development certificate (£292.50) confirms it in writing.
Other councils in Wales
Building control for a 10 to 40 m² extension:
- Newport: £485
- Vale of Glamorgan: £540
- Bridgend: £587
- Gwynedd: £684
- Pembrokeshire: £780
- Ceredigion: £885.60
- Monmouthshire: £1,056
Questions people ask
How much does an extension cost in Conwy?
A mid-range 25 m² single-storey extension in Conwy costs about £57,000 to £70,000 including VAT for the building work, or £2,300 to £2,800 per m², based on Wales prices reviewed in September 2026. With a measured survey, design, a structural engineer, Conwy’s own building control charge and a 15% contingency, plan for £69,500 to £88,500.
How much is building control in Conwy?
Conwy’s own published charge for full plans approval of a 10 to 40 m² extension is £648 (including VAT). Schedule date: 2026-27.
How much does a loft conversion cost in Conwy?
A mid-range 30 m² dormer loft conversion in Conwy costs about £42,500 to £52,000 including VAT for the building work, and about £52,000 to £67,500 with fees, Conwy’s own building control charge and a 15% contingency.
Before you get quotes
- How to compare builders’ quotes line by line
- Plan your whole budget, including the costs people forget
- When quotes arrive, check each one against the typical range for your area
Work in Conwy? Firm listings on Estiquote’s map of checked local firms open soon: see what you’ll need. Listing will be free while we build the map, with at least 30 days’ notice before any charge.