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 Llanelli?
In Llanelli, 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 biggest cost drivers are:
- Roof covering: natural slate costs more
- Front, rear or both
- Scaffolding on busy streets
- Bathrooms and finishes
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 Llanelli?
Here is how the rules work for a mansard loft conversion in Wales. In Wales a mansard roof needs planning permission and is judged against local design guidance.
The Party Wall etc. Act 1996 applies in Wales, so notices must be served before work on a shared wall, on the boundary, or excavation close to a neighbour’s foundations.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
The work we manage on a mansard loft conversion:
- Party wall notices to both neighbours
- Structural design and calculations
- Planning drawings and application
- Staircase and fire-safe escape route
- New roof structure, slate or tile covering and lead work
- Insulation, electrics, plumbing and plastering
How long does it take?
Build time is typically 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 Llanelli
Terraced houses in Welsh towns often have narrow plots, which suits rear and side return extensions and rear dormers.
Projects in Llanelli (SA15) 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
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about mansard loft conversions in Llanelli
Do you build mansard loft conversions in Llanelli?
Yes. We build mansard loft conversions across Llanelli, including postcodes SA15. Every project starts with a free home visit.
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 Llanelli?
In Llanelli, 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.
Do I need planning permission for a mansard loft conversion in Llanelli?
In Wales a mansard roof needs planning permission and is judged against local design guidance.
How long does it take?
Around 9 to 12 weeks on site, plus 2 to 3 months for planning and party wall matters beforehand.
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.