Portishead, Somerset
Semi-detached rear extension in Portishead
Semi-detached rear extension in Portishead: single or two-storey extensions for semi-detached houses, with side access and one party wall. We measure the house, show you what the rules allow, price it in writing and build it.
Portishead sits in Somerset, with postcode districts including BS20. In Portishead 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 Portishead?
A semi-detached rear extension in Portishead is priced at £1,980–£3,220 per square metre including VAT as a guide, before kitchen fit-out and fees. South West prices run slightly above our West Midlands baseline; natural stone to match the house is the main variable.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £23,500–£38,500 |
| 4 m wide × 5 m deep (20 m²) | £39,500–£64,500 |
| 4 m wide × 6 m deep (24 m²) | £47,500–£77,500 |
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 semi-detached rear extension in Portishead?
Whether your semi-detached rear extension in Portishead needs a planning application depends on its size, your house and any local restrictions.
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.
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.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. Before any drawing we look up the property's history with the council, because earlier extensions and removed rights change the answer.
What are homes in Portishead like to extend?
Portishead has Victorian terraces nearer the centre and post-war semis on the edges. Sloping gardens are frequent, which affects floor levels and steps down to the patio.
How a semi-detached rear extension in Portishead comes together
Survey visit
We visit free of charge, measure up, check access, drainage and neighbours' extensions, and note what you want the room to do.
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.
Fixed price and build
A written price for the agreed design, a start date and a named contact through the build, ending with the building control completion certificate.
Semi-detached rear extensions near Portishead
Neighbouring places we cover include Nailsea (3.5 miles) and Clevedon (4.7 miles).
- Semi-detached rear extension in Nailsea
- Semi-detached rear extension in Clevedon
- Semi-detached rear extension in Yatton
- Semi-detached rear extension in Caldicot
- Semi-detached rear extension in Bristol
Other work in Portishead:
FAQ
Semi-detached rear extension questions in Portishead
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.
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.
How long does a semi extension take?
10 to 16 weeks on site for a single-storey extension.
Can you match the brick or stone on my Portishead house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
How much does a semi-detached rear extension cost in Portishead?
As a guide, £1,980–£3,220 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £23,500–£38,500 at that rate. Your written price follows the survey.
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.