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 Carmarthen?
In Carmarthen, 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 Carmarthen 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:
- Number of dormers and lead work
- Scaffolding on busy streets
- Party wall surveyor fees
- Front, rear or both
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 Carmarthen?
Before anything is built in Carmarthen, 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.
We check this for your address before design work starts, so there are no surprises later.
What we handle
The work we manage on a mansard loft conversion:
- Building control sign-off
- Insulation, electrics, plumbing and plastering
- Staircase and fire-safe escape route
- Structural design and calculations
- Dormer windows
- Planning drawings and application
How long does it take?
Expect 9 to 12 weeks on site, after planning approval. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Carmarthen
Wales has many terraced valley streets, stone cottages and post-war estates, so extension designs are shaped by slopes, materials and local character.
Our Carmarthen coverage includes postcode districts SA31, and we also work in nearby places such as Llanelli, Ammanford and Gorseinon.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 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 Carmarthen
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 planning permission for a mansard loft conversion in Carmarthen?
In Wales a mansard roof needs planning permission and is judged against local design guidance.
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.
Who approves a mansard loft conversion in Carmarthen?
Planning matters in Carmarthen go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
How much does a mansard loft conversion cost in Carmarthen?
In Carmarthen, 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.
What roof covering is used?
Natural slate is traditional; some councils accept other materials. We follow local guidance.