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 Richmond?
In Richmond, a mansard loft conversion typically costs £84,500–£123,500 for a typical rear mansard, including VAT at 20% (standard rate). The guide for Richmond reflects typical costs in London, roughly 30% above the UK-wide figure. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear mansard | £84,500–£123,500 |
| Higher specification | £123,500–£154,500 |
What moves the price most:
- Party wall surveyor fees
- Roof covering: natural slate costs more
- Number of dormers and lead work
- Scaffolding on busy streets
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 Richmond?
Before anything is built in Richmond, we confirm which approvals apply in 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.
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:
- Party wall notices to both neighbours
- Insulation, electrics, plumbing and plastering
- Planning drawings and application
- New roof structure, slate or tile covering and lead work
- Staircase and fire-safe escape route
- Dormer windows
How long does it take?
Allow 9 to 12 weeks on site, after planning approval. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Richmond
Many London boroughs have conservation areas and detailed design guides, so early design advice saves time at the planning stage.
We work across Richmond and neighbouring areas such as Hayes, Twickenham and Kingston upon Thames. Postcodes we cover in Richmond include TW9.
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
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about mansard loft conversions in Richmond
How much does a mansard loft conversion cost in Richmond?
In Richmond, a mansard loft conversion typically costs £84,500–£123,500 for a typical rear mansard, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.
Do you build mansard loft conversions in Richmond?
Yes. We build mansard loft conversions across Richmond, including postcodes TW9. Every project starts with a free home visit.
Does a mansard need planning permission?
Almost always, because it changes the roof shape. Councils assess it against local design guidance.
What roof covering is used?
Natural slate is traditional; some councils accept other materials. We follow local guidance.
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.