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 Caernarfon?
In Caernarfon, a mansard loft conversion typically costs £60,000–£87,500 for a typical rear mansard, including VAT at 20% (standard rate). That range is adjusted for Wales, where domestic building work typically costs around 8% below the national average. 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 |
The main things that change the cost:
- Bathrooms and finishes
- Scaffolding on busy streets
- Number of dormers and lead work
- Party wall surveyor fees
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a mansard loft conversion in Caernarfon?
Before anything is built in Caernarfon, we confirm which approvals apply 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.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
On a typical mansard loft conversion we handle:
- Insulation, electrics, plumbing and plastering
- New roof structure, slate or tile covering and lead work
- Dormer windows
- Structural design and calculations
- Staircase and fire-safe escape route
- Party wall notices to both neighbours
How long does it take?
The build itself usually takes 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 Caernarfon
Terraced houses in Welsh towns often have narrow plots, which suits rear and side return extensions and rear dormers.
Projects in Caernarfon (LL55) are surveyed in person before we quote, so the price reflects your actual property.
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 in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about mansard loft conversions in Caernarfon
Do you build mansard loft conversions in Caernarfon?
Yes. We build mansard loft conversions across Caernarfon, including postcodes LL55. Every project starts with a free home visit.
Do I need planning permission for a mansard loft conversion in Caernarfon?
In Wales a mansard roof needs planning permission and is judged against local design guidance.
What roof covering is used?
Natural slate is traditional; some councils accept other materials. We follow local guidance.
How much does a mansard loft conversion cost in Caernarfon?
In Caernarfon, 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.
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.
How long does it take?
Around 9 to 12 weeks on site, plus 2 to 3 months for planning and party wall matters beforehand.