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 Devon?
In Devon, a mansard loft conversion typically costs £66,500–£97,000 for a typical rear mansard, including VAT at 20% (standard rate). Building costs in the South West are close to the UK average, so the figures for Devon are close to our national guide. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear mansard | £66,500–£97,000 |
| Higher specification | £97,000–£121,000 |
The main things that change the cost:
- Bathrooms and finishes
- Front, rear or both
- Scaffolding on busy streets
- Number of dormers and lead work
Use the guide price tool to see how size and specification change the figure, then ask for a written, itemised quote.
Do you need planning permission for a mansard loft conversion in Devon?
The approval route for Devon is set by planning law 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.
Where work involves a shared wall, building on the boundary, or digging foundations within 3 metres of a neighbour’s building and deeper than its foundations (or within 6 metres for deeper work), the Party Wall etc. Act 1996 applies and notices must be served before work starts.
We check this for your address before design work starts, so there are no surprises later.
What we handle
What we take care of:
- Structural design and calculations
- New roof structure, slate or tile covering and lead work
- Insulation, electrics, plumbing and plastering
- Dormer windows
- Building control sign-off
- Planning drawings and application
How long does it take?
Allow 9 to 12 weeks on site, after planning approval. Before that, surveys, drawings and approvals usually take 3 to 4 months, longer if the council asks for changes.
Building in Devon
In parts of the South West, protected landscapes and conservation areas shape what can be built, so materials and roof forms are chosen carefully.
Towns we cover in Devon include Plymouth, Exeter, Paignton, Torquay, Newton Abbot and Exmouth.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 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 handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about mansard loft conversions in Devon
Do you build mansard loft conversions in Devon?
Yes. We build mansard loft conversions across Devon, including postcodes DT7, EX1, EX10, EX11 and EX12. 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 long does it take?
Around 9 to 12 weeks on site, plus 2 to 3 months for planning and party wall matters beforehand.
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 much does a mansard loft conversion cost in Devon?
In Devon, a mansard loft conversion typically costs £66,500–£97,000 for a typical rear mansard, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.