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 Oadby?
In Oadby, a mansard loft conversion typically costs £62,000–£90,000 for a typical rear mansard, including VAT at 20% (standard rate). That range is adjusted for the East Midlands, where domestic building work typically costs around 5% below the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear mansard | £62,000–£90,000 |
| Higher specification | £90,000–£112,500 |
Your quote will depend mainly on:
- Roof covering: natural slate costs more
- Party wall surveyor fees
- Number of dormers and lead work
- 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 Oadby?
Approvals for a mansard loft conversion in Oadby follow the rules for England. In England a mansard almost always needs planning permission because it changes the roof shape. Many councils publish design guidance for mansards on terraced streets, and some streets are more likely to be approved where neighbours already have one.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued 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
Handled as part of most mansard loft conversions:
- Structural design and calculations
- Staircase and fire-safe escape route
- Party wall notices to both neighbours
- Building control sign-off
- New roof structure, slate or tile covering and lead work
- Insulation, electrics, plumbing and plastering
How long does it take?
Expect 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 Oadby
In the East Midlands, many estates built since the 1960s have integral garages that convert well into a study or bedroom.
From LE2 outwards, we take on projects throughout Oadby and the surrounding parts of Leicestershire.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed 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 Oadby
Does a mansard need planning permission?
Almost always, because it changes the roof shape. Councils assess it against local design guidance.
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 a mansard loft conversion take in Oadby?
Typically 9 to 12 weeks on site, after planning approval. Design and approvals beforehand usually take 3 to 4 months.
How much does a mansard loft conversion cost in Oadby?
In Oadby, a mansard loft conversion typically costs £62,000–£90,000 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.
