Single-storey extensions in South Glamorgan

Covering South Glamorgan

Our coverage across South Glamorgan includes Cardiff, Barry, Penarth and Llantwit Major.

Homes in South Glamorgan

Welsh homes include long terraces built into hillsides, stone cottages and modern estates, and sloping sites often shape how and where an extension can go.

What is a single-storey extension?

We design the extension around how you use the house: where the light comes from, how the new room joins the old one, and what happens to the drains and the garden. The structure is built in brick or block to match the house, finished with a flat roof and lantern or a pitched roof, then insulated, plastered and handed back ready to decorate.

Measured survey and design drawings
Building control application and inspections
First-fix and second-fix electrics, plastering and making good

How much should I budget for a single-storey extension?

What single-storey extensions typically cost. These are guide ranges; the written quote for your house replaces them.

Single-storey extensions	Guide price incl. VAT
Standard specification	£2,600 to £3,000 per m²
Good specification	£3,000 to £3,500 per m²
High specification	£3,500 to £4,000 per m²

How is a single-storey extension approved in South Glamorgan?

In Wales the planning rules, including what counts as permitted development, are set by the Welsh Government, and Welsh building regulations differ in places from England’s. We check both against your house before drawings are finalised, and handle party wall notices where needed.

Wales has its own permitted development rules, set by the Welsh Government.

What can change the price or programme?

Drains under the footprint may need diverting or a build-over agreement with the water company.
Large glazed areas need to meet energy rules, which can shape the size of doors and rooflights.

What happens after I enquire?

Tell us about the project. Call, use the guide price tool or send the form with a few photos and a postcode.
Survey at your house. We look at the existing structure, services and access, and agree what the design needs to achieve.
Design and fixed price. You get drawings and a written price for the agreed specification before anything is ordered.
Construction and completion. One site lead co-ordinates every trade through to the building control certificate.

Single-storey extensions: common questions

Can we stay in the house during the build?

Usually yes. We keep the existing house closed off from the works until the knock-through near the end, and agree a temporary kitchen set-up with you if the kitchen is affected.

Do you need to dig up the drains?

Sometimes. If a public sewer runs under the extension, the water company has to agree a build-over or a diversion. We check this at survey stage.

How do I get a price for single-storey extensions in South Glamorgan?

Use the guide price tool for a ballpark figure, then book a visit for a fixed written price for the agreed specification.

Also covering

Learn more about single-storey extensions, or see every project we cover in South Glamorgan.