First-floor extensions in Llangefni

The basics for Llangefni at a glance.

Postcode districts: LL60, LL62, LL63, LL71, LL73, LL74 and nearby districts
County / area: Gwynedd and Anglesey, 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: Menai Bridge (6.2 miles), Bangor (Gwynedd and Anglesey) (7.7 miles), Caernarfon (8.1 miles)
Distance to Bangor (Gwynedd and Anglesey): about 7.7 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.

Around Llangefni we also work in Menai Bridge, Bangor (Gwynedd and Anglesey) and Caernarfon, and across the rest of Gwynedd and Anglesey. Postcode districts in and near Llangefni: LL60, LL62, LL63, LL71, LL73, LL74 and nearby districts.

What it costs in Llangefni

A guide price for Llangefni: around £23,000–£33,500 for 4 m × 3.5 m of new first-floor space (14 m²). That works out at £1,660–£2,390 per m² of new floor space, including VAT at 20%. Design fees, structural calculations and approval fees are separate and listed on our prices page.

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 Llangefni

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 Llangefni 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.

Tying into the house

The new floor and walls must line up with the existing first floor, often through a new opening in the rear wall above the old one. Floor levels, the position of upstairs windows and the existing roof all affect where the opening can go, so we survey both floors carefully.

How we'd run your project

Understand the brief
At your home in Llangefni we agree what you need: bedroom count, bathroom, kitchen space, and how much garden you want to keep.
Design and approvals
We draw the extension and check it against the rules for Wales, then apply for planning permission or a certificate of lawfulness, whichever fits.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Questions about first-floor extensions in Llangefni

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

Llangefni 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.

Who handles building regulations for a project in Llangefni?

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.

Which postcodes do you cover around Llangefni?

We cover Llangefni (LL60, LL62, LL63, LL71, LL73, LL74 and nearby districts) and nearby places including Menai Bridge, Bangor (Gwynedd and Anglesey) and Caernarfon, plus the rest of Gwynedd and Anglesey. The first site visit is free.

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

We also cover places near Llangefni, including:

Other extensions in Llangefni

All two-storey extension services in Llangefni · First-floor extensions across Gwynedd and Anglesey

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