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 Somerset?
In Somerset, a mansard loft conversion typically costs £66,500–£97,000 for a typical rear mansard, including VAT at 20% (standard rate). Prices in the South West sit near the national average for this kind of work, and the range for Somerset reflects that. 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 biggest cost drivers are:
- Number of dormers and lead work
- Roof covering: natural slate costs more
- Scaffolding on busy streets
- Party wall surveyor fees
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 Somerset?
Approvals for a mansard loft conversion in Somerset 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.
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.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
On a typical mansard loft conversion we handle:
- Planning drawings and application
- Dormer windows
- Structural design and calculations
- New roof structure, slate or tile covering and lead work
- Insulation, electrics, plumbing and plastering
- Building control sign-off
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 Somerset
The South West mixes stone and render cottages with post-war and newer estates, and local materials matter more here when matching an extension.
Towns we cover in Somerset include Mendip, Bath, Weston-super-Mare, Taunton, Yeovil and Bridgwater.
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 sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about mansard loft conversions in Somerset
Who approves a mansard loft conversion in Somerset?
Planning matters in Somerset go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
Do I need party wall agreements?
Yes, mansards on terraced houses almost always involve both party walls.
How much does a mansard loft conversion cost in Somerset?
In Somerset, 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.
How long does it take?
Around 9 to 12 weeks on site, plus 2 to 3 months for planning and party wall matters beforehand.
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.