Two-storey extensions in Hertfordshire
Find your town in Hertfordshire, compare extension types and get a guide price in a couple of minutes.
Hertfordshire at a glance
- Nation
- England
- Price region
- East of England
- Postcode areas
- AL, CM, EN, HP, SG, WD
- Main town
- Watford
- Towns listed
- 33
- Site visits
- Free, no obligation
Choose your town
- Watford
- Hemel Hempstead
- Stevenage
- St Albans
- Welwyn Garden City
- Cheshunt
- Hatfield
- Bishops Stortford
- Borehamwood
- Hitchin
- Hoddesdon
- Letchworth Garden City
- North Watford
- Harpenden
- Bushey
- Hertford
- Rickmansworth
- Potters Bar
- Berkhamsted
- Ware
- Croxley Green
- Broxbourne
- West Watford
- Batchworth
- Tring
- Chorleywood
- Codicote
- Baldock
- Abbots Langley
- Waltham Cross
- Holywell (Hertfordshire)
- London Colney
- Leverstock Green
Guide prices in the East of 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.
Towns in Hertfordshire include Watford (WD1), Hemel Hempstead (HP1), Stevenage (SG1), St Albans (AL1), Welwyn Garden City (AL6), Cheshunt (EN7), Hatfield (AL9) and Bishops Stortford (CM23). If yours isn't listed, we still cover it.
Which type suits your house?
Rear, side, wraparound or over the garage: each adds space in a different way. For most houses in Hertfordshire, one or two of these will clearly suit the plot better than the rest, and we'll tell you which.
The rules in England
Hertfordshire 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 Hertfordshire
How much does a two-storey extension cost in Hertfordshire?
In the East of 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 Hertfordshire?
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 Hertfordshire?
Yes. We list the main towns here, but we cover the whole of Hertfordshire 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.