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 Shoreham-by-Sea?
In Shoreham-by-Sea, a mansard loft conversion typically costs £73,000–£106,500 for a typical rear mansard, including VAT at 20% (standard rate). Prices across the South East are typically 12% above the UK average for this kind of work, which is reflected in the range for Shoreham-by-Sea. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear mansard | £73,000–£106,500 |
| Higher specification | £106,500–£133,000 |
What moves the price most:
- Scaffolding on busy streets
- Roof covering: natural slate costs more
- Bathrooms and finishes
- Front, rear or both
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 Shoreham-by-Sea?
Whether you need planning permission depends on your house and its location 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.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
The work we manage on a mansard loft conversion:
- Staircase and fire-safe escape route
- Party wall notices to both neighbours
- Dormer windows
- Structural design and calculations
- Building control sign-off
- Planning drawings and application
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 Shoreham-by-Sea
The South East has a broad mix of housing, from Victorian terraces in the towns to post-war semis and newer estates, so extension types vary street by street.
Shoreham-by-Sea sits in West Sussex, about 6 miles west of Brighton. We cover the whole of Shoreham-by-Sea, including postcodes BN43.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 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 Shoreham-by-Sea
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.
How much does a mansard loft conversion cost in Shoreham-by-Sea?
In Shoreham-by-Sea, a mansard loft conversion typically costs £73,000–£106,500 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 you build mansard loft conversions in Shoreham-by-Sea?
Yes. We build mansard loft conversions across Shoreham-by-Sea, including postcodes BN43. 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.