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 Larne?
In Larne, a mansard loft conversion typically costs £56,000–£81,500 for a typical rear mansard, including VAT at 20% (standard rate). The guide for Larne reflects typical costs in Northern Ireland, roughly 14% below the UK-wide figure. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical rear mansard | £56,000–£81,500 |
| Higher specification | £81,500–£102,000 |
The main things that change the cost:
- Front, rear or both
- Bathrooms and finishes
- Agreements with neighbours on shared walls
- Roof covering: natural slate costs more
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 Larne?
The approval route for Larne is set by planning law in Northern Ireland. In Northern Ireland a mansard needs planning permission from the council.
In Northern Ireland building control approval comes from the council, usually through a full plans application or a building notice, with inspections during the work and a completion certificate at the end.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
The work we manage on a mansard loft conversion:
- Structural design and calculations
- New roof structure, slate or tile covering and lead work
- Written agreement with neighbours on shared walls
- Dormer windows
- Planning drawings and application
- Staircase and fire-safe escape route
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 Larne
Across Northern Ireland, bungalows and chalet bungalows are common, so loft conversions and rear extensions are popular projects.
From BT40 outwards, we take on projects throughout Larne and the surrounding parts of County Antrim.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 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
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about mansard loft conversions in Larne
Do I need planning permission for a mansard loft conversion in Larne?
In Northern Ireland a mansard needs planning permission from the council.
Can I stay at home?
Usually. The new roof is built under a temporary cover so the house stays dry.
What roof covering is used?
Natural slate is traditional; some councils accept other materials. We follow local guidance.
Do you build mansard loft conversions in Larne?
Yes. We build mansard loft conversions across Larne, including postcodes BT40. Every project starts with a free home visit.
How much does a mansard loft conversion cost in Larne?
In Larne, a mansard loft conversion typically costs £56,000–£81,500 for a typical rear mansard, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.
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.