Harpenden, Hertfordshire
Two-storey rear extension in Harpenden
A larger kitchen downstairs and an extra bedroom or bathroom upstairs, under one roof. If you live in Harpenden and want to know what a two-storey rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
Harpenden is covered from our Hertfordshire round, including AL5. Two-storey rear extensions suit semi-detached houses in Harpenden best, where the extra bedroom matters as much as the bigger kitchen.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a two-storey rear extension cost in Harpenden?
Guide prices for a two-storey rear extension in Harpenden start from our East of England rate of £1,910–£2,860 per square metre, including VAT. East of England prices run slightly above our West Midlands baseline; clay soils near trees are the main foundation variable.
| Size | Guide price inc VAT |
|---|---|
| 3 m × 5 m footprint, two floors (30 m²) | £57,000–£86,000 |
| 4 m × 6 m footprint, two floors (48 m²) | £91,500–£137,500 |
We put a fixed price in writing once the design is agreed, and explain any provisional sums such as foundations.
Do you need planning permission for a two-storey rear extension in Harpenden?
The planning route for a two-storey rear extension in Harpenden is set by England's householder rules and your council.
A two-storey rear extension can be permitted development in England only if it projects no more than 3 metres, stays at least 7 metres from the rear boundary, matches the existing roof pitch and has obscure-glazed upper side windows. In practice most double-storey rear extensions go through a householder planning application.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. At the first visit we measure what is there now and tell you which route fits: permitted development, prior approval or a planning application.
What are homes in Harpenden like to extend?
Harpenden mixes Victorian terraces with 1930s semis, so both side returns and full-width kitchen extensions suit houses here.
How a two-storey rear extension in Harpenden comes together
Look round and measure
A free visit to see the back of the house, measure it, check the drains and boundaries and hear what you need.
Design and guide price
Two or three layout options with a guide price for each, so you choose the design knowing what it costs.
Planning and regulations
We take the design through the right planning route, then produce the construction drawings and engineer's calculations for building control.
Build and sign-off
We build to the approved drawings with regular updates, then hand over the building control completion certificate and any guarantees from suppliers.
Two-storey rear extensions near Harpenden
Close by, we work in St Albans, about 4.7 miles away, and Luton, about 5.0 miles away.
- Two-storey rear extension in St Albans
- Two-storey rear extension in Luton
- Two-storey rear extension in Codicote
- Two-storey rear extension in Hemel Hempstead
- Two-storey rear extension in Welwyn Garden City
Other work in Harpenden:
FAQ
Two-storey rear extension questions in Harpenden
What postcode areas do you cover around Harpenden?
Including AL5, and the surrounding Hertfordshire area.
Who will build my extension?
Vetted building teams working under contract to us. Your contract is with S&K Property Investments and Improvement Ltd for the design and the build.
Is two-storey cheaper per square metre than single-storey?
Usually yes, because the foundations and roof are shared across twice the floor area. The total cost is higher.
Can I live at home while the extension is built?
Usually yes. Most of the work is outside until the back wall is opened near the end, and that stage is screened off.
Will I need a structural engineer?
Yes for the beam over the new opening and usually the foundations; we arrange them and their calculations go to building control.
Do I need a party wall agreement?
In England, usually yes if the extension is on or near a shared boundary or the foundations are close to a neighbour's building. We serve the notices.