Mountain Ash, South Wales Valleys
Side return extension in Mountain Ash
Thinking about a side return extension in Mountain Ash? Infilling the narrow passage beside a Victorian or Edwardian back addition. Our team handles the drawings, the planning route and the build, and your contract is with one company throughout.
Mountain Ash sits in the South Wales Valleys, with postcode districts including CF43 and CF45. In Mountain Ash we check the boundary line and the neighbour's gutter before drawing a side return, because a few centimetres decide whether the wall goes on or beside the boundary.
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 side return extension cost in Mountain Ash?
Guide prices for a side return extension in Mountain Ash start from our Wales rate of £2,140–£3,530 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 |
|---|---|
| 2 m wide × 6 m deep (12 m²) | £25,500–£42,500 |
| 2.5 m wide × 7 m deep (17.5 m²) | £37,500–£62,000 |
These are guide ranges; the written quote after the survey is the figure that counts.
Do you need planning permission for a side return extension in Mountain Ash?
Whether your side return extension in Mountain Ash needs a planning application depends on its size, your house and any local restrictions.
Welsh side-extension rules limit a single-storey side addition to 4 metres high and a 50% increase in the width of the original house, with tighter limits in conservation areas. Wraparounds usually need a planning application.
In Wales, as in England, the Party Wall etc. Act 1996 requires notice to neighbours before work to a shared wall or excavation near their foundations.
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 Mountain Ash like to extend?
Stone terraces along the valley floors and post-war semis higher up are typical of Mountain Ash. Sloping sites are common, so floor levels and retaining walls are designed at the start.
How a side return extension in Mountain Ash 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.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
Approvals
Permitted development check or householder planning application, then Building Regulations drawings to the Welsh Approved Documents and structural calculations, plus party wall notices where they apply.
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.
Side return extensions near Mountain Ash
Close by, we work in Treharris, about 3.4 miles away, and Rhondda, about 3.4 miles away.
- Side return extension in Treharris
- Side return extension in Rhondda
- Side return extension in Aberdare
- Side return extension in Merthyr Tydfil
- Side return extension in Nelson
Other work in Mountain Ash:
FAQ
Side return extension questions in Mountain Ash
Can you match the brick or stone on my Mountain Ash house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
What postcode areas do you cover around Mountain Ash?
Including CF43 and CF45, and the surrounding South Wales Valleys area.
Where does the drainage go?
Side passages often carry the soil and rainwater pipes. We survey them first and reroute them under the new floor where needed.
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.
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 you handle building control in Mountain Ash?
Yes. We apply to the council or a registered approver under the Welsh regulations and hand over the completion certificate.