House extension cost in Ireland
A house extension in Ireland costs €1,500 to €2,200 per m² for a single-storey rear extension, €2,000 to €2,500 per m² for two storeys and €2,200 to €3,200 per m² for a wraparound, including VAT. Dublin is higher on every line. Add €5,000 to €10,000 in fees.
Per m² by type and region, and what the bigger extensions that need planning permission cost.
Free, no obligation. One local builder prices it, not five.
- €2,000–€2,500per m² two-storey, incl. VAT
- €2,200–€3,200per m² wraparound
- 66 m²average extension given planning permission in 2025 (CSO)
- 14–24 weekson site for two storeys
Cost per m² by type of extension
| Type | Across Ireland | Dublin |
|---|---|---|
| Single-storey rear | €1,500 to €2,200 per m² | €1,800 to €2,500 per m² |
| Single-storey side or side return | €1,800 to €2,400 per m² | €2,000 to €2,700 per m² |
| Two-storey rear | €2,000 to €2,500 per m² | €2,200 to €2,800 per m² |
| Wraparound (rear and side) | €2,200 to €3,200 per m² | €2,500 to €3,500 per m² |
| High spec or glazed | €2,800 to €3,500 per m² | €3,000 to €4,000 per m² |
Two-storey extensions cost more in total but less per m², because the foundations and the roof are shared by two floors. Count both floors when you work out the area.
Cost per m² by region
| Region | Single-storey per m² |
|---|---|
| Dublin, Kildare, Meath and Wicklow | €1,800 to €2,500 per m² |
| The rest of Leinster | €1,600 to €2,200 per m² |
| Munster | €1,500 to €2,100 per m² |
| Connacht and Ulster | €1,400 to €2,000 per m² |
Dublin and the commuter counties sit 15% to 20% above the national average. The estimator below uses your county's rate.
Plan your extension and see the cost
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A 25 m² single-storey rear extension in Ireland, mid-range, with wide glass doors and a new kitchen: €62,000 to €90,000 all in, including VAT and fees.
How this is worked out
We start from what single-storey extensions cost to build per square metre in each part of Ireland, including VAT at 13.5%, and the rates for side, wraparound, two-storey and heavily glazed extensions. Standard finishes take the lower half of the range, mid-range the upper half, and high spec or a wall of glass the glazed rate. Then we add professional fees (design, engineer, BER) and, if you want one, a new kitchen at your level of finish. Totals are rounded to the nearest €1,000. It's an estimate to plan with, never a quote: the builder prices your house after seeing it.
Three house extensions, priced
- A 20 m² single-storey rear extension in Cork, standard finish, no kitchen: €35,000 to €46,000 all in, including VAT and fees.
- A 40 m² two-storey extension (20 m² down, 20 m² up) in Galway, mid-range, new kitchen: €97,000 to €125,000 all in, including VAT and fees.
- A 35 m² wraparound in Kildare, mid-range, new kitchen: €120,000 to €158,000 all in, including VAT and fees.
Contingency isn't included. Keep 12% to 15% aside.
Over 45 m²: what changes
In 2025, 7,193 planning permissions were granted to extend homes in Ireland, averaging 66 m² each (CSO). These are the extensions too big, too high or in the wrong place to be exempt. In the first half of 2026 there were 3,667, against 3,587 a year earlier.
Over 45 m², three things are added: a planning application (€34 to the council, plus drawings and notices), 8 weeks for the decision and a 4-week appeal period, and building control: a commencement notice with a design certifier and an assigned certifier, or an owner's opt-out.
An extension that changes more than a quarter of the outside of the existing house also counts as a major renovation under the building regulations, so the whole house has to reach a set energy level. Building regulations for extensions explains it.
Two-storey extensions
A two-storey extension puts a bigger kitchen below and a bedroom or bathroom above. Upstairs is where the exemption is tight: 12 m² on a semi-detached or terraced house, 20 m² detached, and 2 m from the party boundary. Most two-storey extensions need planning permission.
Questions people ask
How much does a house extension cost per m² in Ireland?
A house extension in Ireland costs €1,500 to €2,200 per m² for a single-storey rear extension, €2,000 to €2,500 per m² for two storeys and €2,200 to €3,200 per m² for a wraparound, including VAT. Dublin is higher on every line. Add €5,000 to €10,000 in fees.
Is a two-storey extension cheaper per m²?
Yes. €2,000 to €2,500 per m² against €1,500 to €2,200 for single storey at national rates, because two floors share one set of foundations and one roof.
How much does a 40 m² extension cost?
About €89,000 to €123,000 all in at national rates for a single-storey kitchen extension, mid-range, with fees and a kitchen.
Do I need planning permission for a two-storey extension?
Usually. Upstairs the exemption stops at 12 m² on a semi or terrace and 20 m² detached, with windows 8 m from the boundary.
Does an extension add value?
It adds floor area and usually a better kitchen, which is what buyers pay for. Whether it adds more than it costs depends on the area and the house, so ask a local estate agent before you build to sell.
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