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 Porthcawl?
In Porthcawl, 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 Porthcawl 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 |
The main things that change the cost:
- Number of dormers and lead work
- Roof covering: natural slate costs more
- Scaffolding on busy streets
- Bathrooms and finishes
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a mansard loft conversion in Porthcawl?
Before anything is built in Porthcawl, 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:
- New roof structure, slate or tile covering and lead work
- Planning drawings and application
- Party wall notices to both neighbours
- Insulation, electrics, plumbing and plastering
- Dormer windows
- Staircase and fire-safe escape route
How long does it take?
The build itself usually takes 9 to 12 weeks on site, after planning approval. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Porthcawl
Wales has many terraced valley streets, stone cottages and post-war estates, so extension designs are shaped by slopes, materials and local character.
Porthcawl sits in Mid Glamorgan, about 6 miles west of Bridgend. We cover the whole of Porthcawl, including postcodes CF36.
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 pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 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 Porthcawl
Do you build mansard loft conversions in Porthcawl?
Yes. We build mansard loft conversions across Porthcawl, including postcodes CF36. 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.
How much does a mansard loft conversion cost in Porthcawl?
In Porthcawl, 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.
Do I need party wall agreements?
Yes, mansards on terraced houses almost always involve both party walls.
Do I need planning permission for a mansard loft conversion in Porthcawl?
In Wales a mansard roof needs planning permission and is judged against local design guidance.