Caerphilly, South Wales Valleys
Semi-detached rear extension in Caerphilly
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Caerphilly and want to know what a semi-detached rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
Caerphilly sits in the South Wales Valleys, with postcode districts including CF83. In Caerphilly 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 Caerphilly?
For Caerphilly 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 |
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 Caerphilly?
Planning for a semi-detached rear extension in Caerphilly 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 Caerphilly like to extend?
Stone terraces along the valley floors and post-war semis higher up are typical of Caerphilly. Sloping sites are common, so floor levels and retaining walls are designed at the start.
How a semi-detached rear extension in Caerphilly 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.
Drawings and budget
Floor plans and elevations for the options, each with a guide price.
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.
Semi-detached rear extensions near Caerphilly
From Caerphilly, the nearest places we also cover are Rhiwbina (3.2 miles) and Whitchurch (4.3 miles).
- Semi-detached rear extension in Rhiwbina
- Semi-detached rear extension in Whitchurch
- Semi-detached rear extension in Risca
- Semi-detached rear extension in Pontypridd
- Semi-detached rear extension in Nelson
Other work in Caerphilly:
FAQ
Semi-detached rear extension questions in Caerphilly
Can I get a price without a visit?
Our online guide-price tool gives a range in a couple of minutes. A written price needs a survey.
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.
What if my neighbour has already extended?
That can make a matching depth easier to justify. We measure theirs at the survey.
Do I need planning permission for a rear extension in Caerphilly?
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.
Is the site visit in Caerphilly free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
Do you handle building control in Caerphilly?
Yes. We apply to the council or a registered approver under the Welsh regulations and hand over the completion certificate.