Two-storey extensions for semi-detached houses in Llantrisant
Thinking about a two-storey extension for a semi-detached house in Llantrisant? We design it, take it through the approvals it needs and build it, with one team responsible from the first visit to the final certificate.
Before you start in Llantrisant, here's what applies.
- Postcode districts
- CF72
- County / area
- Mid Glamorgan, Wales
- Price region
- Wales
- Guide price
- £51,500–£69,500 (£1,840–£2,480 per m²)
- Approval route
- Depends on position: rear (3 m first floor, 10.5 m to the boundary) and some side extensions (10.5 m, 1 m set-back) can be permitted development in Wales.
- Nearest towns
- Beddau (1.2 miles), Pontyclun (1.5 miles), Llanharan (2.8 miles)
- Distance to Rhondda
- about 8.8 miles
- First visit
- Free, no obligation
About a two-storey extension for a semi-detached house
A two-storey extension for a semi-detached house is a two-floor addition to the rear, the open side, or both, designed around the attached neighbour on one side. The rear is often the simplest option and can sometimes be permitted development, while a side extension uses the gap on the detached side. Both need care with the shared party wall and the neighbour's light.
We cover postcode district CF72 in and around Llantrisant, along with neighbouring Beddau, Pontyclun and Llanharan.
What it costs in Llantrisant
Expect a two-storey extension for a semi-detached house in Llantrisant to land somewhere around £51,500–£69,500 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Our Wales guide rate is £1,840–£2,480 per m², including VAT. We'll give you a written design-stage price first, then a fixed build price once the drawings are agreed.
| Spec | Per m² | A 4 m × 3.5 m footprint on two floors (28 m² of new floor space) |
|---|---|---|
| Essential | £1,690–£2,290 per m² | £47,500–£64,000 |
| Standard | £1,840–£2,480 per m² | £51,500–£69,500 |
| Premium | £2,210–£2,980 per m² | £62,000–£83,500 |
Planning and building regulations in Llantrisant
In Wales, a semi can take a two-storey rear extension under permitted development with the ground floor up to 4 m and the first floor up to 3 m beyond the original rear wall, 10.5 m from the rear boundary. A side extension can also be permitted development if it is 10.5 m from the side boundary, set back 1 m and adds no more than 50% width. Otherwise the fee is £585.
Approval in Wales: Householder planning application: £585. Councils normally decide householder applications within 8 weeks.
Building regulations: Building regulations approval under the Welsh Approved Documents, which differ from England's in places (notably energy efficiency).
Design points for Llantrisant homes
Rear, side or both
On a semi, a rear extension sits against the attached neighbour, while a side extension faces the detached neighbour and the street. We compare the space, cost and approval route for each, and for a wraparound, before you commit to one design.
The attached neighbour's light
A two-storey rear extension next to the party wall can take light from the neighbour's rear windows. Councils often use a 45-degree test, so the first floor may need to be shorter than the ground floor or set in from the shared boundary.
How we'd run your project
Visit and first ideas
One of our team visits your house in Llantrisant, checks the walls, roof and drains, and sketches out options with you.
Drawings, then consent
We draw the scheme, check it against the rules in Wales, and take it through the right consent with the council.
Structure and building control
A structural engineer sizes the foundations and steels, and we get building regulations approval before work starts.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.
Questions about two-storey extensions for semi-detached houses in Llantrisant
How much does a two-storey extension for a semi-detached house cost in Llantrisant?
Our guide for Wales, which covers Llantrisant, is £1,840–£2,480 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £51,500–£69,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Which postcodes do you cover around Llantrisant?
We cover Llantrisant (CF72) and nearby places including Beddau, Pontyclun and Llanharan, plus the rest of Mid Glamorgan. The first site visit is free.
How long does a two-storey extension for a semi-detached house take?
Allow 4 to 8 weeks for survey and design, then the approval period (councils normally decide householder applications within 8 weeks), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.
What if my neighbour has already extended?
That often helps. An existing extension next door can reduce the effect of yours on their light, and may show what the council accepts on your street. It can also mean building alongside their wall, so we check its position, foundations and any windows facing your plot at the survey.
Will a side extension make my semi look like a terrace?
It can if it fills the whole gap to the boundary at first floor and the neighbour does the same. Many councils ask for a first-floor gap to the side boundary or a set-back for this reason. We design the extension to keep the semi reading as one of a pair.
Nearby
Nearby towns we cover for two-storey extensions for semi-detached houses:
Other extensions in Llantrisant
- Rear
- Side
- Wraparound
- Part two-storey
- Over a garage
- First floor
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Llantrisant · Two-storey extensions for semi-detached houses across Mid Glamorgan
Book a free site visit in Llantrisant and we'll tell you what's possible, what approvals you need and what the design stage would cost.