Two-storey extensions for semi-detached houses in Merthyr Tydfil
Adding a two-storey extension for a semi-detached house in Merthyr Tydfil gives you two new rooms stacked on one footprint. Here's how we'd approach it, what it typically costs and the rules that apply in Wales.
Quick reference for homeowners in Merthyr Tydfil.
- Postcode districts
- CF47 and CF48
- 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
- Abercanaid (1.8 miles), Aberdare (3.8 miles), Rhymney (4 miles)
- Distance to Rhondda
- about 6.9 miles
- First visit
- Free, no obligation
About a two-storey extension for a semi-detached house
This service suits you if you own a semi-detached house and want to add bedrooms and living space without moving. On a semi, the main questions are which side to build on and how to treat the attached neighbour. You get a survey, design options, the approvals your nation needs and the build, carried out by vetted teams working under S&K.
We cover postcode districts CF47 and CF48 in and around Merthyr Tydfil, along with neighbouring Abercanaid, Aberdare and Rhymney.
What it costs in Merthyr Tydfil
Most of the cost of a two-storey extension for a semi-detached house is set by its size and specification. For Merthyr Tydfil and the rest of Wales, our guide is £1,840–£2,480 per m² including VAT, so about £51,500–£69,500 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.
| 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 Merthyr Tydfil
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 Merthyr Tydfil homes
Keeping the pair balanced
Semis are designed as matching pairs, and a side extension changes that balance. Setting the side extension back from the front wall and keeping its ridge lower helps the pair still read as a pair, which councils' design guides commonly ask for.
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
Free site visit
We visit your home in Merthyr Tydfil, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
Get it approved
Once you're happy with the design we submit it to the council for Merthyr Tydfil and deal with any questions from the planning officer.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the building control completion certificate at the end.
Questions about two-storey extensions for semi-detached houses in Merthyr Tydfil
Which postcodes do you cover around Merthyr Tydfil?
We cover Merthyr Tydfil (CF47 and CF48) and nearby places including Abercanaid, Aberdare and Rhymney, plus the rest of Mid Glamorgan. The first site visit is free.
Who handles building regulations for a project in Merthyr Tydfil?
We handle it as part of the project. What's needed in Wales: building regulations approval under the Welsh Approved Documents, which differ from England's in places (notably energy efficiency). We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.
How much does a two-storey extension for a semi-detached house cost in Merthyr Tydfil?
Our guide for Wales, which covers Merthyr Tydfil, 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.
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.
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.
Nearby
The same service in neighbouring towns:
Other extensions in Merthyr Tydfil
- 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 Merthyr Tydfil · Two-storey extensions for semi-detached houses across Mid Glamorgan
Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.