Covering Gwynedd and Anglesey
Our coverage across Gwynedd and Anglesey includes Bangor, Holyhead, Caernarfon and Llangefni.
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 goes into a basement conversion?
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.
- Damp and structural survey
- Underpinning or lowering the floor where needed
- Finished floors, walls and ceilings
How much should I budget for a basement conversion?
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 |
How is a basement conversion approved in Gwynedd and Anglesey?
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.
In Wales an existing cellar conversion usually does not need planning permission; new excavation and lightwells may.
What can affect a basement conversion?
- Groundwater levels drive the waterproofing design and cost.
- A pump for the drainage system needs a battery back-up.
What are the steps?
- Start with a conversation. A short call or the online form is enough for us to understand what you want to build.
- We visit and measure. A surveyor checks the house, the boundaries and the ground, and discusses what is realistic.
- Price and paperwork. The design is priced line by line, and we submit the planning and building control applications.
- We build it. Work follows an agreed programme, with inspections at each stage and a final sign-off.
Your questions answered
How long does it take?
About 6 to 12 weeks for a cellar conversion and 16 to 30 weeks for a new basement.
Will my neighbours be affected?
New basements usually need party wall agreements. We handle the notices and surveyors.
Do you work in Gwynedd and Anglesey?
Yes. Gwynedd and Anglesey is within our coverage for basement and cellar conversions, along with nearby Bangor and Holyhead.
Also covering
- Basement and cellar conversions in Bangor
- Basement and cellar conversions in Holyhead
- Basement and cellar conversions in Caernarfon
- Basement and cellar conversions in Llangefni
- Basement and cellar conversions in Pwllheli
Learn more about basement and cellar conversions, or see every project we cover in Gwynedd and Anglesey.