Cost Guide
House Extension Cost Guide
Real fixed-price ranges for every extension type we build across Dublin and Ireland, broken down by size and by project — so you know roughly what to budget before your free site survey.
How much does a house extension cost?
Budget EUR 2,400 to EUR 3,200 per square metre for a fully fitted house extension in Dublin — groundworks, structure, glazing, kitchen or bathroom fit-out, flooring and decoration all included. That per-square-metre rate is the number every size and project estimate below is built from; every quote we give is a single fixed price, confirmed after a free site survey.
Elsewhere in Leinster, typical costs run slightly lower at EUR 2,200 to EUR 2,900 per square metre. Along the M1 corridor — Drogheda, Balbriggan and the towns we cover directly — we charge the same rate as central Dublin, with no travel premium.
Cost by size
Single-storey extensions, from a small side-return up to the 40 sqm limit under exempted development.
| Size | Typical project | Price range |
|---|---|---|
| 8 - 12 sqm | Small side-return extension | EUR 40,000 - 55,000 |
| 15 - 20 sqm | Small rear extension | EUR 50,000 - 75,000 |
| 20 sqm | Standard rear extension | EUR 55,000 - 75,000 |
| 30 sqm | Rear or kitchen extension | EUR 75,000 - 105,000 |
| 40 sqm | Largest single storey under exempted development | EUR 100,000 - 140,000 |
| 30 - 50 sqm | Two-storey extension | EUR 130,000 - 220,000 |
Cost by project type
Kitchen extensions, attic conversions, two-storey extensions, garage conversions and full renovations — the projects we build most often.
| Project | Detail | Price range |
|---|---|---|
| Kitchen extension | 30 - 40 sqm, fully fitted | EUR 80,000 - 130,000 |
| Attic conversion - Velux | Roof windows only, no roofline change | EUR 30,000 - 45,000 |
| Attic conversion - Dormer | Bedroom + ensuite, full standing height | EUR 45,000 - 65,000 |
| Attic conversion - Hip-to-gable | Semi-detached / end-of-terrace, max floor area | EUR 60,000 - 80,000+ |
| Two-storey extension | 30 - 50 sqm split across both floors | EUR 130,000 - 220,000 |
| Garage conversion | Single-bay, attached garage | EUR 18,000 - 35,000 |
| Full home renovation | Rewire, replumb, layout changes | Priced per project - free survey |
What changes the price
- Structure — timber-frame construction is typically faster and can be cheaper than traditional block-built and steel-frame structures, though steel gives the widest open-plan spans.
- Glazing — full-width bi-fold doors or a glass roof typically add EUR 8,000 to EUR 15,000 over a standard window and door specification.
- Finish level — kitchen units, flooring and sanitaryware specification move the final number more than almost any other factor.
- Site access & party walls — narrow side access, shared boundary walls and existing drainage all affect groundworks cost and timeline.
- Planning complexity — a project that needs full planning permission (rather than exempted development) adds design and application time before construction starts.
Every figure above is a typical range, not a quote — we confirm your fixed price after a free site survey. For specific cost and planning questions, see our full FAQ page.
Get Your Fixed-Price Quote
A free site survey gives you a real number for your home — not just a range.