Two-storey extensions in Dorset
Two-storey extensions in Dorset: guide prices for South West England, the rules that apply in England, and the towns we cover.
Dorset at a glance
- Nation
- England
- Price region
- South West England
- Postcode areas
- BH, DT, SP
- Main town
- Bournemouth
- Towns listed
- 16
- Site visits
- Free, no obligation
Choose your town
- Bournemouth
- Poole
- Weymouth
- Christchurch
- Ferndown
- Dorchester
- Wimborne Minster
- Canford Heath
- Verwood
- Portland
- Bridport
- Blandford Forum
- Swanage
- Broadstone
- Parkstone
- Sherborne
Guide prices in South West England
| Extension type | Per m² | Typical project |
|---|---|---|
| Two-storey rear extension | £2,060–£2,780 per m² | £57,500–£78,000 |
| Two-storey side extension | £2,110–£2,830 per m² | £88,500–£119,000 |
| Two-storey wraparound extension | £2,210–£3,040 per m² | £124,000–£170,000 |
| Part single, part two-storey | £2,060–£2,830 per m² | £74,000–£102,000 |
| Extension over a garage | £1,800–£2,630 per m² | £32,500–£47,500 |
| First-floor extension over an existing single storey | £1,850–£2,680 per m² | £26,000–£37,500 |
| Two-storey front extension | £2,270–£3,090 per m² | £27,000–£37,000 |
Including VAT, Standard spec. See all prices and fees.
Across Dorset we cover Bournemouth (BH1), Poole (BH15), Weymouth (DT3), Christchurch (BH6), Ferndown (BH22), Dorchester (DT1), Wimborne Minster (BH21) and Canford Heath (BH11), plus the smaller places around them.
Which type suits your house?
The boundaries usually decide it. Two-storey work close to a neighbour needs careful design for light and privacy, so at the visit in Dorset we measure distances to every boundary before suggesting a type.
The rules in England
Dorset is in England. Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission. 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.
The full England rules explained
Extension types
- Two-storey rear extensions
- Two-storey side extensions
- Two-storey wraparound extensions
- Part single, part two-storey extensions
- Extensions over a garage
- First-floor extensions
- Two-storey front extensions
By house type
- Two-storey extensions for semi-detached houses
- Two-storey extensions for detached houses
- Two-storey extensions for end-of-terrace houses
Rooms and uses
- Kitchen extensions with bedrooms above
- Extra bedroom and en-suite extensions
- Two-storey annexe extensions
- Garage conversions with a room above
Design and approvals
- Two-storey extension plans and drawings
- Planning permission for two-storey extensions
- Structural engineering for two-storey extensions
- Building regulations for two-storey extensions
- Party wall notices for extensions
- Design and build two-storey extensions
Questions about extensions in Dorset
How much does a two-storey extension cost in Dorset?
In South West England our guide for a two-storey rear extension is £2,060–£2,780 per m² including VAT, about £57,500–£78,000 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Side and wraparound extensions cost a little more per m².
Do I need planning permission in Dorset?
Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission. 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).
Do you cover the whole of Dorset?
Yes. We list the main towns here, but we cover the whole of Dorset including villages. The first site visit is free.
What happens at the first visit?
We look at your house, the boundaries, access and drains, talk through what you need and explain the approvals. Then we price the design stage, including the measured survey, in writing.