What is a mansard loft conversion?
A mansard loft conversion rebuilds the roof with a nearly vertical slope (about 72 degrees) and a flat top, effectively adding a new storey. Small dormer windows sit within the steep slope. Mansards are common on period terraces in towns and cities.
How much does a mansard loft conversion cost in Bangor, Gwynedd?
In Bangor, a mansard loft conversion typically costs £60,000–£87,500 for a typical rear mansard, including VAT at 20% (standard rate). Building costs in Wales run about 8% below the UK average, and the figures for Bangor are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear mansard | £60,000–£87,500 |
| Higher specification | £87,500–£109,500 |
Your quote will depend mainly on:
- Bathrooms and finishes
- Roof covering: natural slate costs more
- Scaffolding on busy streets
- Number of dormers and lead work
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a mansard loft conversion in Bangor, Gwynedd?
Whether you need planning permission depends on your house and its location in Wales. In Wales a mansard roof needs planning permission and is judged against local design guidance.
Building regulations in Wales are set by the Welsh Government. Approval comes from the council’s building control service or a registered building control approver, with inspections during the work and a completion certificate at the end.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
Handled as part of most mansard loft conversions:
- Planning drawings and application
- Building control sign-off
- Staircase and fire-safe escape route
- Structural design and calculations
- Party wall notices to both neighbours
- Insulation, electrics, plumbing and plastering
How long does it take?
Allow 9 to 12 weeks on site, after planning approval. Design and approvals come first and typically take 3 to 4 months, depending on the approval route.
Building in Bangor, Gwynedd
Wales has many terraced valley streets, stone cottages and post-war estates, so extension designs are shaped by slopes, materials and local character.
Bangor sits in Gwynedd. We cover the whole of Bangor, including postcodes LL57.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about mansard loft conversions in Bangor, Gwynedd
Do you build mansard loft conversions in Bangor?
Yes. We build mansard loft conversions across Bangor, including postcodes LL57. Every project starts with a free home visit.
What roof covering is used?
Natural slate is traditional; some councils accept other materials. We follow local guidance.
Do I need planning permission for a mansard loft conversion in Bangor?
In Wales a mansard roof needs planning permission and is judged against local design guidance.
Why choose a mansard over a dormer?
A mansard gives more usable floor space and a neater appearance from the street, but costs more and needs planning permission.
Do I need party wall agreements?
Yes, mansards on terraced houses almost always involve both party walls.
How much does a mansard loft conversion cost in Bangor?
In Bangor, a mansard loft conversion typically costs £60,000–£87,500 for a typical rear mansard, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.