England
Rear extensions in Hertfordshire
Across Hertfordshire we handle the whole rear extension: survey, drawings, the planning route, building control and the build. Towns we cover here include Watford, Hemel Hempstead and Stevenage.
What are homes in Hertfordshire like to extend?
Hertfordshire mixes Victorian terraces with 1930s semis, so both side returns and full-width kitchen extensions suit houses here.
Rear extension prices in Hertfordshire
East of England prices run slightly above our West Midlands baseline; clay soils near trees are the main foundation variable. Per square metre including VAT, standard specification:
| Extension | Per m² |
|---|---|
| Single-storey rear extension | £2,010–£3,290 |
| Two-storey (per m² across both floors) | £1,910–£2,860 |
| Side return | £2,440–£4,030 |
| Wraparound | £2,330–£3,820 |
| Glass-led | £2,970–£5,090 |
Planning and building rules in Hertfordshire
Under England's householder permitted development rules you can usually add 3 metres at the back of an attached house, or 4 metres on a detached house, without a planning application, as long as the extension stays under 4 metres high and its eaves stay under 3 metres where it is within 2 metres of a boundary.
England also has the larger home extension route: a single-storey rear extension of up to 6 metres on an attached house or 8 metres on a detached house, after prior approval from the council. The council notifies your neighbours and has 42 days to decide; the fee is £249 (£310 for applications made from 8 December 2026). The route is not available on designated land such as conservation areas.
Planning and Building Regulations are separate in England: even a permitted development extension is inspected for foundations, drainage, structure, insulation, fire safety and ventilation, through the council or a registered building control approver, ending with a completion certificate.
Because rear extensions often sit on or near the boundary, the Party Wall etc. Act 1996 usually applies in England. Notices go out one or two months before work depending on the type of work, and a surveyor's award is only needed if a neighbour does not consent.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent.
Rear extensions we build in Hertfordshire
- Building Regulations for rear extensions
- Single-storey rear extensions
- Two-storey rear extensions
- Kitchen-diner rear extensions
- Side return extensions
- Wraparound extensions
- Glazed and glass-box rear extensions
- Rear extensions for terraced houses
- Rear extensions for semi-detached houses
- Rear extensions for detached houses
- Rear extensions for bungalows
- Flat-roof rear extensions
- Pitched and lean-to roof rear extensions
- Knocking through to a rear extension
- Roof lanterns and rooflights for rear extensions
- Permitted development rear extensions
- Larger home extension prior approval (England)
- Rear extension plans and planning applications
Towns and districts in Hertfordshire
The main places we cover in Hertfordshire include Watford, Hemel Hempstead and Stevenage, across postcode areas AL, CM, EN, HP, SG and WD.
| Town | Postcode districts | Nearest town we also cover |
|---|---|---|
| Watford | WD1, WD17, WD18 | West Watford (0.9 miles) |
| Hemel Hempstead | HP1, HP2, HP3 | Abbots Langley (3.6 miles) |
| Stevenage | SG1, SG2 | Codicote (3.9 miles) |
| St Albans | AL1, AL2 | Abbots Langley (4.7 miles) |
| Welwyn Garden City | AL7, AL8 | Hatfield (2.8 miles) |
| Cheshunt | EN7, EN8, EN10 | Waltham Cross (1.0 miles) |
| Hatfield | AL9, AL10 | Welwyn Garden City (2.8 miles) |
| Bishops Stortford | CM23 | Harlow (6.8 miles) |
| Borehamwood | WD6 | Barnet (3.3 miles) |
| Hitchin | SG6 | Letchworth Garden City (3.2 miles) |
- 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
- Enfield Lock
- Royston
- Croxley Green
- Broxbourne
- West Watford
- Batchworth
- Tring
- Chorleywood
- Codicote
- Baldock
- Abbots Langley
- Waltham Cross
Areas near Hertfordshire
FAQ
Questions people ask
How much does a rear extension cost in Hertfordshire?
As a guide, £2,010–£3,290 per square metre including VAT for a standard single-storey extension at East of England rates.
Do I need planning permission in Hertfordshire?
Often not for a single-storey rear extension of up to 3 metres (4 metres on a detached house) under permitted development, or up to 6 or 8 metres with prior approval, unless the house is in a conservation area or its rights have been removed.
Which towns in Hertfordshire do you cover?
32 towns and districts, including Watford, Hemel Hempstead and Stevenage.
Do you handle building control?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.