House Extension Cost Calculator
A finished single-storey extension in Dublin typically costs around €2,500–€3,500 per square metre including VAT, before a kitchen. Use the calculator for an estimate based on your size, extension type and level of finish.
- Typical €2,500–€3,500 per m²
- Single and two-storey extensions
- Fees and kitchen included as options
- Free quotes from vetted builders
What affects the cost?
- Size: the biggest factor, though smaller extensions cost more per square metre.
- Single or two storey: two-storey extensions cost more overall but often less per square metre.
- Finish: standard, mid-range or high-end glazing, flooring and fittings.
- Structure: steel beams, openings into the house and foundations.
- Access and ground conditions: tight sites and poor ground add cost.
- Fees: design, engineering and certification typically add 8–12%.
Extension cost calculator
Get a guide range for your extension based on typical 2026 Dublin prices, including VAT.
A guide only. Your quote will depend on your property, access, structure and the finishes you choose.
Typical costs at a glance
| Extension | Typical cost |
|---|---|
| 20m² single-storey, standard finish | €55,000–€70,000 |
| 25m² single-storey, mid-range finish | €70,000–€90,000 |
| 30m² two-storey | €85,000–€115,000 |
| Kitchen (optional) | €15,000–€40,000 |
Prices are indicative 2026 Dublin ranges including VAT, before any kitchen unless stated.
Planning and timelines
Many rear extensions are exempt from planning permission within set limits. See our guide to planning permission for extensions. A typical single-storey extension takes 12–16 weeks on site, plus design and approval time beforehand.
Frequently asked questions
How much does an extension cost per square metre in Dublin?
Roughly €2,500–€3,500 per square metre including VAT for a finished extension, before a kitchen.
How accurate is the calculator?
It gives a guide range based on typical 2026 Dublin prices. Your actual quote depends on your property, design and finishes.
Does the estimate include VAT?
Yes, at 13.5%, the rate that usually applies to building work.
Are there grants for extensions?
Not usually for the extension itself, but SEAI grants may help with insulation, heat pumps and windows in the rest of the house.
Find vetted contractors for this work
By area:
- North Dublin City: Artane, Cabra, Clontarf, Coolock, Drumcondra, East Wall, Fairview, Glasnevin, Phibsborough, Stoneybatter
- Dún Laoghaire & South Coast: Blackrock, Booterstown, Monkstown, Dún Laoghaire, Dalkey, Killiney
- Dublin North Coast: Raheny, Baldoyle, Donaghmede, Howth, Sutton, Portmarnock, Malahide
- South West Dublin: Tallaght, Citywest, Firhouse, Knocklyon, Ballyboden, Templeogue, Walkinstown, Kimmage, Rathfarnham, Terenure
- West Dublin & Leixlip: Chapelizod, Palmerstown, Lucan, Leixlip, Adamstown, Clondalkin
- Dublin 15: Blanchardstown, Castleknock, Mulhuddart, Ongar, Hansfield, Ashtown
- South Dublin City: Ballsbridge, Donnybrook, Sandymount, Ranelagh, Rathgar, Harold's Cross, Churchtown, Dundrum
- Stillorgan, Sandyford & Foxrock: Mount Merrion, Stillorgan, Goatstown, Sandyford, Cherrywood, Cabinteely, Foxrock, Deansgrange
- North County Dublin: Swords, Lusk, Rush, Skerries
Get free quotes from vetted contractors
Tell us what you're planning, where the property is and when you'd like to start. We'll match you with a vetted local contractor. For anything urgent, call 083 056 8710.
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