Treharris, South Wales Valleys
Semi-detached rear extension in Treharris
For homes in Treharris, 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.
Treharris sits in the South Wales Valleys, with postcode districts including CF46. In Treharris 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 Treharris?
Guide prices for a semi-detached rear extension in Treharris start from our Wales rate of £1,770–£2,880 per square metre, including VAT. 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 Treharris?
Whether your semi-detached rear extension in Treharris needs a planning application depends on its size, your house and any local restrictions.
The Welsh Government's householder rules let many homes add a single-storey rear extension up to 4 metres deep and 4 metres high without a planning application. Deeper projects go through a householder application, because Wales has no prior approval route.
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. At the first visit we measure what is there now and tell you which route fits: permitted development or a householder planning application.
What are homes in Treharris like to extend?
Stone terraces along the valley floors and post-war semis higher up are typical of Treharris. Sloping sites are common, so floor levels and retaining walls are designed at the start.
How a semi-detached rear extension in Treharris 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.
Paperwork handled
Planning or permitted development, Building Regulations approval, structural design and party wall notices are all handled by us.
Written price, then build
Once the design and approvals are in place, you get a fixed written price and programme, and we build through to sign-off.
Semi-detached rear extensions near Treharris
Close by, we work in Nelson, about 1.2 miles away, and Gelligaer, about 2.2 miles away.
- Semi-detached rear extension in Nelson
- Semi-detached rear extension in Gelligaer
- Semi-detached rear extension in Mountain Ash
- Semi-detached rear extension in Bargoed
- Semi-detached rear extension in Blackwood
Other work in Treharris:
FAQ
Semi-detached rear extension questions in Treharris
Do I need a party wall agreement?
In Wales, usually yes if the extension is on or near a shared boundary or close to a neighbour's foundations. We serve the notices.
Do you handle building control in Treharris?
Yes. We apply to the council or a registered approver under the Welsh regulations and hand over the completion certificate.
Can I match pebbledash or render?
Yes. Many semis are refinished with new render across the whole back elevation so old and new match.
How much does a semi-detached rear extension cost in Treharris?
As a guide, £1,770–£2,880 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £21,000–£34,500 at that rate. Your written price follows the survey.
Do I need planning permission for a rear extension in Treharris?
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 Treharris free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.