Llantrisant, South Wales Valleys
Semi-detached rear extension in Llantrisant
For homes in Llantrisant, a semi-detached rear extension is often the simplest way to gain space without moving. Single or two-storey extensions for semi-detached houses, with side access and one party wall. We take it from survey to completion certificate.
Llantrisant and its postcode districts CF38 and CF72 are part of our South Wales Valleys coverage. Where a Llantrisant semi already has a small lean-to at the back, we usually replace it rather than extend it.
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 Llantrisant?
For Llantrisant 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 |
These are guide ranges; the written quote after the survey is the figure that counts.
Do you need planning permission for a semi-detached rear extension in Llantrisant?
Whether your semi-detached rear extension in Llantrisant needs a planning application depends on its size, your house and any local restrictions.
In Wales a single-storey rear extension can often be permitted development if it projects no more than 4 metres beyond the rear wall and is no more than 4 metres high. Wales has no prior approval route for deeper extensions, so anything bigger needs a householder planning application.
In Wales a rear extension of more than one storey can be permitted development if the ground floor projects no more than 4 metres and the upper floor no more than 3 metres, with at least 10.5 metres to the rear boundary. It is not permitted development in conservation areas, National Parks or National Landscapes, so many double-storey schemes need a householder application.
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 Llantrisant like to extend?
Stone terraces along the valley floors and post-war semis higher up are typical of Llantrisant. Sloping sites are common, so floor levels and retaining walls are designed at the start.
How a semi-detached rear extension in Llantrisant 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.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
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 Llantrisant
Neighbouring places we cover include Pontypridd (4.5 miles) and Tonypandy (6.6 miles).
- Semi-detached rear extension in Pontypridd
- Semi-detached rear extension in Tonypandy
- Semi-detached rear extension in Whitchurch
- Semi-detached rear extension in Rhiwbina
- Semi-detached rear extension in Caerphilly
Other work in Llantrisant:
FAQ
Semi-detached rear extension questions in Llantrisant
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.
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.
Do I need a party wall agreement?
Usually with the attached neighbour, in England and Wales.
Do you handle building control in Llantrisant?
Yes. We apply to the council or a registered approver under the Welsh regulations and hand over the completion certificate.
Can you match the brick or stone on my Llantrisant house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
How long does a rear extension take to build in Llantrisant?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.