Multi-Generational Self-Build in Ireland — A 245 m² Galway Build, the Numbers and the Gotchas
On this page
Multi-generational (Co. Galway, 245 m², 2023): €640,000 build, main contractor. Two self-contained units under one roof.
Multi-generational in Co. Galway: 245 m², finished 2023, main contractor. Build cost: €640,000 (€2,610/m²). Two self-contained units under one roof: main 4-bed (165 m²) + granny flat 1-bed (80 m²). Shared utility, separate entrances, separate metering. Build: timber frame, slate roof, MVHR in both units, 9 kW air-to-water heat pump, 6 kWp solar PV. Gotchas: the granny flat needed separate metering (BER A1 for the main house + BER A3 for the granny flat), planning for the dual use (the planner wanted the granny flat to be removable, not a permanent separate dwelling), soundproofing between the units (the wall between is double-stud with acoustic insulation). Outcome: finished in 14 months. The granny flat is currently used by the owner's mother; will become a teenager's retreat in 5 years. The owners credit the success to: a clear brief that named the multi-generational use, an architect with two recent multi-gen builds, and a quantity surveyor who caught the metering issue early.
When this matters most
You're researching case studies for a multi-generational build.
When this doesn't apply
You've already started your build.
Sources
SCSI, Construction Cost Database 2024. https://www.scsi.ie/
Frequently asked questions
How much did a 245 m² multi-gen build cost in Galway in 2023?
€640,000 build, main contractor. Build cost €2,610/m². Two units: main 4-bed (165 m²) + granny flat 1-bed (80 m²). Total project cost €850,000–€900,000.
What were the gotchas on this build?
The granny flat needed separate metering (BER A1 + BER A3 for the two units), planning for the dual use (removable, not a permanent separate dwelling), soundproofing between the units.
How long did the build take?
14 months on site. The dual-unit design and the metering added 2 months. The granny flat is currently used by the owner's mother; will become a teenager's retreat in 5 years.
When this matters most
You're researching case studies for a multi-generational build.
When this doesn't apply
You've already started your build.
Where to go next
Watch out for
Common mistakes, hidden costs, gotchas.
- 1970s Bungalow Retrofit in Ireland — A 142 m² Wexford Build, the Numbers and the Gotchas →
- A-Rated ICF Self-Build in Ireland — A 210 m² Wicklow Build, the Numbers and the Gotchas →
- Coastal Passive House in Ireland — A 195 m² Cork Build, the Numbers and the Gotchas →
- Rural Bungalow Self-Build in Ireland — A 165 m² Westmeath Build, the Numbers and the Gotchas →
- Urban Infill Self-Build in Dublin — A 132 m² Dublin 6 Build, the Numbers and the Gotchas →