Basement and cellar conversions in Bangor, Gwynedd and Anglesey

Covering Bangor, Gwynedd and Anglesey

Bangor, Gwynedd and Anglesey is about 8 miles north-east of Caernarfon. We also cover Llangefni (8 miles to the west), Caernarfon and Colwyn Bay.

Homes in Gwynedd and Anglesey

Across Wales you find valley terraces, coastal towns, rural stone houses and newer estates, so access, slopes and local materials all feature in the design.

What is included in a basement conversion in Bangor, Gwynedd and Anglesey?

Everything below ground depends on keeping water out. We design the waterproofing system (usually a cavity drain membrane with a pump, or tanking) to the relevant British Standard guidance, then add insulation, ventilation, light and an escape route. New basements involve underpinning and a party wall process and are designed with a structural engineer.

Underpinning or lowering the floor where needed
Ventilation, heating and electrics
Finished floors, walls and ceilings

What is the guide price for a basement conversion in Bangor, Gwynedd and Anglesey?

What basement and cellar conversions typically cost. These are guide ranges; the written quote for your house replaces them.

Basement and cellar conversions	Guide price incl. VAT
Existing cellar conversion	£1,900 to £3,000 per m²
New basement excavation	£4,200 to £6,600 per m²

Do you need permission for a basement conversion in Bangor, Gwynedd and Anglesey?

Welsh projects need planning clearance from the council under Welsh rules, building regulations approval under the Welsh approved documents, and party wall notices where the work affects a neighbour’s wall or foundations.

In Wales an existing cellar conversion usually does not need planning permission; new excavation and lightwells may.

What should I think about before starting?

Groundwater levels drive the waterproofing design and cost.
Headroom of about 2.1 m or more is needed, which may mean lowering the floor.

What are the steps?

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.
Price and paperwork. The design is priced line by line, and we submit the planning and building control applications.
Build and hand over. Our teams build to the programme, building control inspects, and you get the completion paperwork at the end.

What people ask before starting

How much does a basement conversion cost?

Converting an existing cellar costs about £1,900 to £3,000 per square metre including VAT. A new excavated basement is around £4,200 to £6,600 per square metre.

Will my neighbours be affected?

New basements usually need party wall agreements. We handle the notices and surveyors.

Do you work in Bangor, Gwynedd and Anglesey?

Yes. Bangor, Gwynedd and Anglesey is within our coverage for basement and cellar conversions, along with nearby Llangefni and Caernarfon.

Basement and cellar conversions in nearby towns

Learn more about basement and cellar conversions, or see every project we cover in Bangor.