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 Antrim?
In Antrim, a dormer loft conversion typically costs £41,500–£58,500 for a typical rear dormer with en-suite, including VAT at 20% (standard rate). That range is adjusted for Northern Ireland, where domestic building work typically costs around 14% below the national average. 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 |
The biggest cost drivers are:
- Built-in storage and finishes
- Fire safety upgrades to the existing house
- Staircase position
- Scaffolding and access
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 dormer loft conversion in Antrim?
Approvals for a dormer loft conversion in Antrim follow the rules for 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.
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
Handled as part of most dormer loft conversions:
- Dormer structure, roof covering and windows
- Building control completion certificate
- New staircase and fire-safe escape route
- Written agreement with neighbours on shared walls
- Insulation, plastering, electrics and plumbing
- Measured survey and head-height check
How long does it take?
Allow 6 to 9 weeks on site. Before that, surveys, drawings and approvals usually take 6 to 12 weeks, longer if the council asks for changes.
Building in Antrim
Northern Ireland has many detached and semi-detached homes on generous plots, which suits single-storey rear extensions and garage conversions.
If your home is in Antrim or close by in Ballymena, Newtownabbey and Belfast, a free home visit is the first step.
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 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 dormer loft conversions in Antrim
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.
How much does a dormer loft conversion cost in Antrim?
In Antrim, 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.
Do I need planning permission for a dormer loft conversion in Antrim?
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.
Do you build dormer loft conversions in Antrim?
Yes. We build dormer loft conversions across Antrim, including postcodes BT41. Every project starts with a free home visit.
How long does it take?
Usually 6 to 9 weeks on site.
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.