What is a dormer loft conversion?
A dormer loft conversion adds a box-shaped structure to the rear roof slope, creating vertical walls and full headroom across most of the new room. It is the most common loft conversion in the UK because it works on terraced, semi-detached and detached houses.
How much does a dormer loft conversion cost in Belfast?
In Belfast, a dormer loft conversion typically costs £41,500–£58,500 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). The guide for Belfast 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 dormer with en-suite | £41,500–£58,500 |
| Higher specification | £58,500–£73,000 |
Your quote will depend mainly on:
- En-suite or bathroom
- Staircase position
- Dormer size and roof structure
- Scaffolding and access
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a dormer loft conversion in Belfast?
Before anything is built in Belfast, we confirm which approvals apply in Northern Ireland. In Northern Ireland a rear dormer can be permitted development if it does not face a road, sits no higher than the ridge and is set back at least 0.5 metres from the ridge, eaves, party wall and verges. Roof enlargements are not permitted development in conservation areas.
Northern Ireland has no Party Wall Act. Work on shared walls relies on agreement with the neighbour and common law, so we agree the arrangements in writing 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
What we take care of:
- Dormer structure, roof covering and windows
- Insulation, plastering, electrics and plumbing
- Drawings and structural calculations
- Measured survey and head-height check
- New staircase and fire-safe escape route
- Steel beams and new floor joists
How long does it take?
The build itself usually takes 6 to 9 weeks on site. Design and approvals come first and typically take 6 to 12 weeks, depending on the approval route.
Building in Belfast
Across Northern Ireland, bungalows and chalet bungalows are common, so loft conversions and rear extensions are popular projects.
We work across Belfast and neighbouring areas such as Newtownabbey, Lisburn and Newtownards. Postcodes we cover in Belfast include BT1, BT2, BT3 and BT4.
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
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 dormer loft conversions in Belfast
How much does a dormer loft conversion cost in Belfast?
In Belfast, a dormer loft conversion typically costs £41,500–£58,500 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.
Will I need to move out?
No. Most of the work is done from scaffolding and the roof. The new staircase is formed near the end, which causes a few days of disruption.
How much head height do I need?
Ideally at least 2.2 metres from the top of the ceiling joists to the underside of the ridge. Less can still work with a dormer, but we check this at the survey.
Do I need planning permission for a dormer loft conversion in Belfast?
In Northern Ireland a rear dormer can be permitted development if it does not face a road, sits no higher than the ridge and is set back at least 0.5 metres from the ridge, eaves, party wall and verges. Roof enlargements are not permitted development in conservation areas.
What fire safety is required?
Building regulations require a safe escape route. Converting a two-storey house to three storeys usually means a protected stairway with fire doors to habitable rooms and mains-wired smoke alarms.
How long does a dormer loft conversion take in Belfast?
Typically 6 to 9 weeks on site. Design and approvals beforehand usually take 6 to 12 weeks.