How Much Does a House Extension Cost in Ireland?
Adding an extension is one of the best ways to create extra space without moving house. Costs in Ireland vary significantly depending on size, specification, and location. Here's a realistic guide for 2026.
These figures are researched Irish market estimates for budgeting. Costs vary by project scope, materials and county; get at least three written quotes before starting work.
Typical builder - extensions costs
- Single storey extension (per sqm): €1,800–€2,800 — Basic spec, standard finish
- Single storey extension (per sqm, high spec): €2,800–€4,000+ — High-end finishes, underfloor heating, bifolds
- Two storey extension (per sqm): €1,500–€2,500 — More efficient per sqm than single storey
- Garage conversion to living space: €15,000–€30,000 — Insulation, flooring, plumbing if adding bathroom
- Attic conversion: €25,000–€50,000 — Staircase, dormer, Velux, bedroom or office
- Architect and planning fees: €3,000–€8,000 — For extensions over 40sqm or those requiring planning
What affects the cost?
- Size of the extension — the larger the extension, the lower the cost per square metre
- Specification level — standard vs premium finishes make a huge difference
- Site access — difficult access can increase groundwork and material costs
- Ground conditions — poor ground may require additional foundations
- County — Dublin and major cities tend to be 15–25% more expensive
- Planning permission — required for extensions over 40sqm at ground floor
Tips before hiring
- Get your architect or structural engineer involved early — before getting builder quotes
- Consider a single storey extension at the rear to avoid planning complications
- Extensions under 40sqm on the rear or side of a house are usually exempt from planning
- Get at least 3 builder quotes and ask to see previous completed extensions
Frequently asked questions
- Do I need planning permission for an extension in Ireland? Under Exempted Development rules, single-storey extensions of up to 40sqm to the rear of a house can be built without planning permission, subject to conditions. Extensions over 40sqm, two-storey extensions, and extensions to the front usually require planning permission.
- How long does an extension take to build in Ireland? A standard single-storey extension of 20–30sqm typically takes 10–16 weeks to complete from breaking ground to final finish.
- What is the best type of extension for adding value in Ireland? A kitchen/dining extension to the rear of a house typically adds the most value relative to cost. Open plan living space is highly sought after in the Irish property market.