First-floor extensions in Tenby

Tenby: the key facts for this kind of project.

Postcode districts: SA70
County / area: Dyfed, Wales
Price region: Wales
Guide price: £23,000–£33,500 (£1,660–£2,390 per m²)
Approval route: It may be permitted development if the ground floor goes no more than 4 m and the first floor no more than 3 m beyond the original rear wall, with the first floor 10.5 m from the rear boundary.
Nearest towns: Saundersfoot (2.5 miles), Pembroke (8.9 miles), Pembroke Dock (10.2 miles)
Distance to Llanelli: about 23.3 miles
First visit: Free, no obligation

About a first-floor extension

A first-floor extension is a new upstairs room built on top of an existing single-storey part of your house, such as a rear kitchen extension, a utility or a side annexe. It adds a bedroom, bathroom or study without enlarging the footprint. Whether it works depends mainly on whether the walls and foundations below can carry the extra load.

Tenby sits about 23.3 miles from Llanelli. Closer to home, Saundersfoot is 2.5 miles away and Pembroke 8.9 miles.

What it costs in Tenby

In Wales, which includes Tenby, we'd expect a first-floor extension to cost around £23,000–£33,500 for 4 m × 3.5 m of new first-floor space (14 m²), or £1,660–£2,390 per m² including VAT. These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.

Spec	Per m²	4 m × 3.5 m of new first-floor space (14 m²)
Essential	£1,520–£2,200 per m²	£21,500–£31,000
Standard	£1,660–£2,390 per m²	£23,000–£33,500
Premium	£1,990–£2,870 per m²	£28,000–£40,000

Planning and building regulations in Tenby

In Wales, a first floor over a rear extension can be permitted development if it goes no more than 3 m beyond the original rear wall and stays at least 10.5 m from the rear boundary, with the ground floor within 4 m. Over a side extension, the 10.5 m, 1 m set-back and 50% width tests apply. Otherwise a householder application costs £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 Tenby homes

Escape and fire safety

A new first-floor bedroom needs an escape window with a clear opening of at least 0.33 m², at least 450 mm wide and 450 mm high, with the bottom no more than 1,100 mm above the floor, unless there is a protected route to the stairs.

Can the existing structure take it?

Many single-storey extensions were built with foundations, walls and lintels sized for one storey. We find out what is there with trial holes and, where available, the original building control drawings. The engineer then decides whether to reuse, strengthen or rebuild parts of the structure.

How we'd run your project

Start at your house
We come to your home in Tenby, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in Wales before drawing in detail.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

Questions about first-floor extensions in Tenby

Which postcodes do you cover around Tenby?

We cover Tenby (SA70) and nearby places including Saundersfoot, Pembroke and Pembroke Dock, plus the rest of Dyfed. The first site visit is free.

Do I need planning permission for a first-floor extension in Tenby?

Tenby is in Wales, so Wales planning rules apply. It may be permitted development if the ground floor goes no more than 4 m and the first floor no more than 3 m beyond the original rear wall, with the first floor 10.5 m from the rear boundary. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.

How much does a first-floor extension cost in Tenby?

Our guide for Wales, which covers Tenby, is £1,660–£2,390 per m² including VAT. A typical project with 4 m × 3.5 m of new first-floor space (14 m²) comes to about £23,000–£33,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Can I build on top of my existing single-storey extension?

Often yes, but only after the structure has been checked. Foundations, walls and lintels built for one storey may not carry two. We dig trial holes, look for the original building control approval and ask the structural engineer to confirm what can stay, what needs strengthening and what must be rebuilt.

What happens to the room below while the first floor is built?

The old roof is removed, so the room below is exposed for a short period. We fit temporary weather protection, plan the work so the roof comes off only when the new structure is ready, and agree with you which rooms will be out of use and for roughly how long.

Nearby

Other towns near Tenby:

Other extensions in Tenby

All two-storey extension services in Tenby · First-floor extensions across Dyfed

Ready to talk it through? Call us or send the form and we'll arrange a visit to your home in Tenby.