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 Gwent?
In Gwent, 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 |
What moves the price most:
- Party wall surveyor fees
- Roof covering: natural slate costs more
- Bathrooms and finishes
- Front, rear or both
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 Gwent?
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
On a typical mansard loft conversion we handle:
- Staircase and fire-safe escape route
- Dormer windows
- Party wall notices to both neighbours
- Insulation, electrics, plumbing and plastering
- Building control sign-off
- New roof structure, slate or tile covering and lead work
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 Gwent
Wales has many terraced valley streets, stone cottages and post-war estates, so extension designs are shaped by slopes, materials and local character.
Towns we cover in Gwent include Newport, Cwmbran, Pontypool, Ebbw Vale, Risca and Abergavenny.
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 Gwent
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.
Do you build mansard loft conversions in Gwent?
Yes. We build mansard loft conversions across Gwent, including postcodes CF3, CF83, NP10, NP19 and NP20. Every project starts with a free home visit.
How much does a mansard loft conversion cost in Gwent?
In Gwent, 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 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 Gwent?
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.