Stevenage, Hertfordshire
Semi-detached rear extension in Stevenage
Single or two-storey extensions for semi-detached houses, with side access and one party wall. We design, get the approvals for and build rear extensions for semi-detached houses in Stevenage and the surrounding area, with one contract from the first survey to building control sign-off.
Stevenage and its postcode districts SG1 and SG2 are part of our Hertfordshire coverage. In Stevenage we measure the attached neighbour's extension at the survey, because it often sets the sensible depth for yours.
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 semi-detached rear extension cost in Stevenage?
For Stevenage we work from the East of England rate: £2,010–£3,290 per square metre of new floor, including VAT, standard specification. 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 wide × 4 m deep (12 m²) | £24,000–£39,500 |
| 4 m wide × 5 m deep (20 m²) | £40,500–£65,500 |
| 4 m wide × 6 m deep (24 m²) | £48,500–£79,000 |
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 for a semi-detached rear extension in Stevenage?
The planning route for a semi-detached rear extension in Stevenage is set by England's householder rules and your council.
In England a single-storey rear extension can often be built under permitted development: up to 3 metres beyond the original rear wall of an attached house, or 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres if any part is within 2 metres of a boundary.
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.
If 3 or 4 metres is not enough, England's prior approval route allows 6 metres on a terraced or semi-detached house and 8 metres on a detached house for a single-storey rear extension. Neighbours are consulted, the council decides within 42 days, and the fee is £249, rising to £310 from 8 December 2026.
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 Stevenage like to extend?
Post-war semis and newer estates are typical of Stevenage, 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.
How a semi-detached rear extension in Stevenage comes together
Free site visit
We measure the house and garden, look at the back wall, drainage and boundaries, and talk through what you want from the space.
Drawings and budget
Floor plans and elevations for the options, each with a guide price.
Paperwork handled
Planning, prior approval or permitted development, Building Regulations approval, structural design and party wall notices are all handled by us.
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.
Semi-detached rear extensions near Stevenage
Neighbouring places we cover include Codicote (3.9 miles) and Hitchin (4.8 miles).
- Semi-detached rear extension in Codicote
- Semi-detached rear extension in Hitchin
- Semi-detached rear extension in Letchworth Garden City
- Semi-detached rear extension in Baldock
- Semi-detached rear extension in Welwyn Garden City
Other work in Stevenage:
FAQ
Semi-detached rear extension questions in Stevenage
What postcode areas do you cover around Stevenage?
Including SG1 and SG2, and the surrounding Hertfordshire area.
How long does a rear extension take to build in Stevenage?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
Do I need a party wall agreement?
Usually with the attached neighbour, in England and Wales.
Can you match the brick or stone on my Stevenage house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
Is the site visit in Stevenage free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
How much does a semi-detached rear extension cost in Stevenage?
As a guide, £2,010–£3,290 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £24,000–£39,500 at that rate. Your written price follows the survey.