Hertfordshire
Rear extension plans and planning applications in Hertfordshire
Measured survey, design options, planning drawings and the application, handled for you. 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.
For Watford homes we start with a measured survey, then draw options before anything is submitted. Post-war semis and newer estates are typical of Hertfordshire, and many have room for a full-width extension. Shrinkable clay is common in the East of England, so foundations near trees and hedges are designed to NHBC-style depth guidance.
What does it cost in Hertfordshire?
As a guide, £1,000–£2,500 including VAT. Ground conditions, glazing, the roof and how far the house is opened up move the final figure within the range.
Do you need planning permission in Hertfordshire?
England's rules allow a rear extension of more than one storey without an application only when it is no deeper than 3 metres and at least 7 metres from the boundary opposite the rear wall, and never on designated land. Most two-storey schemes need householder planning permission.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent.
A householder planning application in England costs £548 (£575 for applications made from 8 December 2026), and a lawful development certificate for proposed work costs half the householder fee.
Councils aim to decide householder applications within 8 weeks of validation, and prior approval within 42 days.
Where in Hertfordshire do we work?
- 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
FAQ
Questions people ask
Do I need an architect?
You need accurate drawings by someone who knows householder planning; we provide them.
Can I see the design in 3D?
Yes; we produce simple 3D views so you can judge the size and light.
What if planning is refused?
We review the reasons with you, amend and resubmit (often free of a second fee within 12 months in England) or appeal.
Do you cover all of Hertfordshire?
We cover 32 towns and districts in Hertfordshire, including Watford, Hemel Hempstead and Stevenage.
Who builds the extension?
Vetted building teams working under contract to us; your contract is with S&K Property Investments and Improvement Ltd.