Penarth, Cardiff and the Vale
Semi-detached rear extension in Penarth
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 Penarth and the surrounding area, with one contract from the first survey to building control sign-off.
Penarth and its postcode districts CF64 are part of our Cardiff and the Vale coverage. In Penarth 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 Penarth?
For Penarth we work from the Wales rate: £1,770–£2,880 per square metre of new floor, including VAT, standard specification. Prices in Wales sit below our West Midlands baseline; sloping sites are the main variable.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £21,000–£34,500 |
| 4 m wide × 5 m deep (20 m²) | £35,500–£57,500 |
| 4 m wide × 6 m deep (24 m²) | £42,500–£69,000 |
Your written price follows a measured survey and an agreed design, so it reflects your house, not an average.
Do you need planning permission for a semi-detached rear extension in Penarth?
Planning for a semi-detached rear extension in Penarth follows the Welsh householder rules.
Welsh permitted development allows a single-storey rear extension of up to 4 metres in depth and 4 metres in height, subject to boundary and garden-coverage limits. There is no larger-extension prior approval scheme in Wales.
Welsh rules allow a two-storey rear extension without an application only where the ground floor is no deeper than 4 metres, the upper floor no deeper than 3 metres and at least 10.5 metres remains to the rear boundary. Most homeowners still apply for householder planning permission.
Conservation areas, National Parks and National Landscapes restrict permitted development in Wales, and listed buildings 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 Penarth like to extend?
Older terraces near the centre and post-war semis further out are typical of Penarth. Sloping sites are common in Wales, so floor levels and retaining walls are designed at the start.
How a semi-detached rear extension in Penarth 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 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 Penarth
We also build rear extensions for semi-detached houses in nearby Cardiff (2.9 miles) and Whitchurch (5.4 miles).
- Semi-detached rear extension in Cardiff
- Semi-detached rear extension in Whitchurch
- Semi-detached rear extension in Barry
- Semi-detached rear extension in Rhiwbina
- Semi-detached rear extension in Caerphilly
Other work in Penarth:
FAQ
Semi-detached rear extension questions in Penarth
Do I need planning permission for a rear extension in Penarth?
Often not for a single-storey rear extension of up to 4 metres under Welsh permitted development. Wales has no prior approval route for deeper extensions.
How long does a rear extension take to build in Penarth?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
What if my neighbour has already extended?
That can make a matching depth easier to justify. We measure theirs at the survey.
What postcode areas do you cover around Penarth?
Including CF64, and the surrounding Cardiff and the Vale area.
Do you handle building control in Penarth?
Yes. We apply to the council or a registered approver under the Welsh regulations and hand over the completion certificate.
Is the site visit in Penarth free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.