Attic Conversion Cost in Ireland: A 2026 Price Guide

I'm Michael Casey, founder of Keystone Roofing. I'm a roofer, not a conversion contractor — but the roof is the part of an attic conversion that decides whether the new room stays warm, dry and legal, and it's the part I get asked about on site every week. This guide covers full Irish attic conversion costs in 2026, then goes deep on the roof-side work: roof windows, dormer weatherproofing, insulation and ventilation — the parts my team actually does.

Attic conversion cost by type

Conversion type	Typical 2026 cost (ex-VAT)	What you get
Storage conversion (floor + ladder + light)	€5,000–€10,000	Floored attic, safe access, basic insulation. Not a habitable room.
Rooflight conversion	€18,000–€28,000	Habitable room with fixed stairs, 1–3 roof windows, full insulation. No change to the roofline.
Dormer conversion	€40,000–€60,000	Rear dormer adds full-height floor area, usually fits a bedroom + ensuite.
Hip-to-gable / full roof remodel	€55,000–€75,000+	Changes the roof shape itself — common on semi-ds with hipped roofs.

Ex-VAT ranges from across the Irish market in 2026. Quotes vary with stairs position, structural steel, ensuite spec and finish level — always compare written, itemised scopes.

What actually drives the total?

• Stairs. A proper fixed stairs (required for a habitable room) usually means stealing space from a landing or bedroom below. Straight flights are cheapest; turns and winders add joinery cost.
• Structural floor. Ceiling joists in most Irish houses were sized to hold a ceiling, not a floor. New structural joists or steel are standard on habitable conversions.
• Dormer size and finish. A wider dormer costs more to build and weatherproof, but cost per usable square metre usually improves with size.
• Insulation standard. Meeting current Part L values at rafter level costs more than a basic job and is worth every cent — this is the room's comfort for decades.
• Ensuite and electrics. Plumbing a bathroom into an attic adds €5,000–€10,000 to most projects.
• Fire compliance. Escape windows, fire doors and mains smoke/heat detection are not optional on a habitable conversion.

The roof side — where conversions succeed or fail

Most conversion horror stories trace back to the roof: a rooflight that leaks at the flashing, a dormer flat roof ponding water, or a warm room that sweats condensation into the rafters because nobody detailed the ventilation. These are the line items to interrogate on any quote.

Roof windows

Rooflight conversions live and die by their windows. A centre-pivot roof window with the matched flashing kit for your roof covering is the correct spec — budget €1,100–€2,000 per window supplied and fitted, with the full breakdown in our Velux and skylight cost guide. Wind-driven rain off the Atlantic finds any shortcut in the flashing, so this is not the line to save €100 on. Our skylight windows service covers exactly this work.

Dormer roof and cheeks

A dormer is a small building on the side of your roof: flat roof on top, clad cheeks on the sides, and junctions into the existing roof covering on three sides. The flat roof wants a single-ply membrane (EPDM) or GRP fibreglass — the same systems we fit on extensions, priced in our flat roof cost guide. The cheeks want proper weatherboarding or tile hanging with a ventilated cavity. Cheeks clad flat against the insulation with no cavity are where dormers rot.

Insulation and ventilation

A habitable conversion needs insulation at rafter level (a warm roof) with a continuous 50mm ventilated air gap between insulation and felt, or a breathable membrane detailed correctly. Skip the ventilation path and the room will condense — the symptoms look exactly like a leak, and our attic condensation guide shows how often the two get confused. Insulation work done as part of the project can qualify for the SEAI attic insulation grant — see what SEAI grants actually cover — and our roof insulation service handles this scope directly.

Tie-in to the existing roof

Cutting a dormer into an older roof often exposes tired felt and battens around the opening. If the main roof is within 5 years of needing replacement, it's usually cheaper to do both at once than to scaffold twice — our roof replacement cost guide gives the 2026 ranges for the wider job.

Planning permission and building regulations

A rooflight conversion with windows on the rear slope is generally exempt from planning permission in Ireland. A rear dormer is usually exempt too, provided it stays within the conditions and size limits for exempted development. Front-slope dormers, hip-to-gable changes and anything on a protected structure need permission. Building regulations apply to every habitable conversion regardless of planning status — structure, stairs, fire escape and insulation all have to comply. The current exemption conditions are on Citizens Information; when in doubt, Cork City or County Council's planning desk will confirm in writing.

How long does an attic conversion take?

A rooflight conversion runs 3–5 weeks once on site. A dormer conversion is typically 6–8 weeks. Hip-to-gable or projects with an ensuite run 8–12 weeks. The roof-side elements — windows, dormer weatherproofing, insulation — sit in the first half of the programme, because everything internal waits on the structure being weathertight.

Is an attic conversion worth it in 2026?

Against the cost of moving house in Cork — stamp duty, legal fees, and the price gap between a 3-bed and a 4-bed — a dormer conversion frequently pencils out, and it adds a bedroom without losing garden. The caveats: use a contractor who itemises the roof-side work properly, get the building-reg compliance in writing, and don't convert an attic under a roof that needs replacing anyway without pricing both together.