StructuralEngineer.ie's summary of the attic conversion regulations in Ireland: a converted attic is a habitable room only if it meets the Building Regulations for one. That covers structure (Part A), fire safety and escape (Part B), stairs (Part K), ventilation (Part F) and energy (Part L). Since 27 July 2026, many side and rear dormers no longer need planning permission.
There are two separate sets of rules: planning, which is about how it looks from outside, and the Building Regulations, which are about whether it’s safe and usable as a room. An attic can be exempt from planning and still fail the Building Regulations.
Planning: dormers and rooflights
- Rear and side dormers are newly exempt from July 2026, within limits reported as about 30 m³ of added volume, no higher than the ridge, and set back from the eaves.
- Front dormers still need planning permission.
- Hip-to-gable conversions change the roof profile. Check whether yours falls inside the dormer exemption.
- Protected structures, ACAs and some estates have restrictions. Check before relying on the exemption.
Building Regulations: what a habitable attic needs
Structure (Part A). A floor designed for habitable loads (1.5 kN/m² imposed under I.S. EN 1991-1-1, plus finishes and partitions), replacement structure for any cut trusses or struts, and support for the stair and dormer.
Headroom. A commonly used benchmark is 2.4 m over at least half the floor area, measured from the new floor level. Check it against the current guidance and your designer’s advice.
Fire and escape (Part B). A protected route from the attic to an exit, fire-rated doors (typically FD30) to habitable rooms off the stair, and smoke alarms. The exact arrangement depends on the house layout.
Stairs (Part K). Pitch, rise, going and headroom over the stair. Space-saving stairs are only allowed in limited cases.
Ventilation and energy (Parts F and L). Windows or rooflights for ventilation and light, and insulation to current standards.
Is BCAR involved?
Attic conversions in an existing house are usually not caught by the BCAR statutory certification regime, but the Building Regulations apply in full. An engineer’s opinion of compliance with Part A, based on inspections during the work, is the usual evidence at sale.
Bottom line
Planning decides whether you can build the dormer. The Building Regulations decide whether the result is a bedroom. Get the structure and the stair designed first. To check your attic and get a fixed fee, call 01 270 9764.
Want a fixed fee for your job? Call 01 270 9764.
Callback the same working day. Fixed fee confirmed in writing before the visit.
Frequently asked questions
Can I call my converted attic a bedroom?
Only if it complies with the Building Regulations for a habitable room: structure, fire safety and escape, stairs, ventilation and energy. Otherwise it is marketed as attic storage.
Do Velux rooflights need planning permission?
Rooflights to the rear are generally exempt. Front rooflights and anything on a protected structure or in some estates can need permission. Check before installing.
Do I need an engineer for an attic conversion?
For a habitable room, yes in practice. The existing ceiling joists can't carry bedroom loads, trussed roofs can't be cut without replacement structure, and the stair opening has to be trimmed. The engineer's opinion of compliance supports the room at sale.
Sources
Get a fixed engineering fee
Two short steps. We call back the same working day.
Prefer to talk? Call 01 270 9764. A live person answers during office hours.