What a house extension costs in Ireland
Expect €1,500 to €2,200 per m² for a one-storey house extension in Ireland and €2,000 to €2,500 per m² for two storeys, counting both floors, with VAT at 13.5% included. Dublin rates are €1,800 to €2,500 and €2,200 to €2,800. Drawings, the engineer and the BER add €5,000 to €10,000. All in, a 20 m² ground-floor room comes to €42,000 to €54,000 and a 40 m² two-storey extension with an en-suite to €105,000 to €128,000.
Rates per m² by type and county, the costs that sit on top, and five house extensions priced from start to finish.
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- €1,500–€2,200per m² for one storey, VAT in
- €2,000–€2,500per m² for two storeys, both floors counted
- €5,000–€10,000drawings, engineer and BER
- 12–15%contingency to hold back
Our price guide
VAT at 13.5% included, for building work in 2026.
| Extension or item | Cost, VAT included | What moves it |
|---|---|---|
| Single-storey extension behind the house | €1,500–€2,200 per m², Dublin €1,800–€2,500 | The county and the finish. Dublin, Kildare, Meath and Wicklow run highest. |
| Two-storey extension, per m² of both floors | €2,000–€2,500 per m², Dublin €2,200–€2,800 | Two floors share one dig and one roof, which brings the rate per m² down. |
| Side extension | €1,800–€2,400 per m², Dublin €2,000–€2,700 | A narrow site, walls along the boundary, and a planning application every time. |
| Wraparound, back and side in an L | €2,200–€3,200 per m², Dublin €2,500–€3,500 | A steel frame to open two sides of the house, and glass that turns the corner. |
| Mostly glass, or a high-end finish | €2,800–€3,500 per m², Dublin €3,000–€4,000 | Sliding walls of glass, roof lanterns, frameless glazing and top-end finishes. |
| Garage conversion, priced as one job | €15,000–€45,000 | Insulation, the old door opening built up, heating, wiring and the finish. |
| En-suite or bathroom fit-out | €4,000–€40,000 | The fittings, how much is tiled, and the distance to the soil pipe. |
| Drawings, engineer and BER | €5,000–€10,000 | Higher with a planning application, or with certifiers above 45 m². |
| Steel where the new rooms open into the house | €2,000–€4,000 | How wide the opening in the old wall is. The beam alone. |
| A new kitchen, supplied and fitted | €5,000–€40,000 | Units, worktops and fitting, from budget to high-end. |
All figures include VAT at 13.5% and round to the nearest €1,000. Hold back 12% to 15% of the total for what turns up once the old walls are opened.
What's included
- The new rooms built to today's building regulations: foundations, floor slab, walls, roof, windows and outside doors
- Wiring, plumbing, heating and plaster inside the new space
- 13.5% VAT on all of the building work
- Left out of the per m² rates: fees, the steel into the old house, en-suite fittings and any kitchen
What pushes it up or down
- The county: Dublin and its commuter counties cost most to build in, Connacht and Ulster least
- Going up: per m², a second storey costs less than spreading out on one floor
- Glass: a wall of sliding or folding doors puts the build on the glazed rate
- A bathroom far from the existing drains, poor ground, or no room for a digger to get in
- Over 45 m², upstairs or at the side: a planning application adds fees and weeks
Five house extensions, priced
- A 16 m² ground-floor bedroom with an en-suite at the back, standard finish, in Galway: build €22,500 to €27,000, fees €5,000 to €10,000, en-suite €4,000 to €8,000. All in €32,000 to €45,000, with €4,000 to €7,000 kept aside.
- A 20 m² single-storey family room at the back, mid-range, national rates: build €37,000 to €44,000, fees €5,000 to €10,000. All in €42,000 to €54,000, with €5,000 to €8,000 kept aside.
- A 40 m² two-storey extension, a room below and a bedroom with an en-suite above, mid-range, national rates: build €90,000 to €100,000, fees €5,000 to €10,000, en-suite €10,000 to €18,000. All in €105,000 to €128,000, with €12,500 to €19,000 kept aside.
- A 30 m² side extension in Dublin, mid-range: build €70,500 to €81,000, fees €5,000 to €10,000. All in €76,000 to €91,000, with €9,000 to €13,500 kept aside.
- A 45 m² wraparound in Kildare, mid-range, opened into the house with a steel beam: build €135,000 to €157,500, fees €5,000 to €10,000, steel €2,000 to €4,000. All in €142,000 to €172,000, with €17,000 to €26,000 kept aside.
The planner on this page works out the same sum for your house, county and finish.
Plan your house extension
Four quick taps, and your plan fills in as you answer: what it costs, whether it needs planning permission and how long it takes. Contact details come last, and only if you want a builder to price it.
25 m² single-storey rear, mid-range finish: €52,000 to €65,000, including VAT and fees.
How the estimate is worked out
Every kind of extension has a build rate per m² for each region of Ireland, VAT at 13.5% included. A standard finish uses the lower half of that range and mid-range the upper half; high spec or a wall of glass moves the build to the glazed rate. Design, engineer and BER fees go on top, with anything you tick (an en-suite, a kitchen, a steel beam into the house) priced at your finish. A garage conversion gets one price for the whole job, since the walls and roof are already standing. Totals are rounded to the nearest €1,000. Use it to plan with. It isn't a quote: a builder prices your house after seeing it.
What it costs in each county
Rates track house prices. Dublin, Kildare, Meath and Wicklow are the dearest places to build, then the rest of Leinster, then Munster, with Connacht and Ulster the least expensive. The table prices one plan in every county: 40 m² over two floors, mid-range, with an en-suite upstairs.
| County | One storey, per m² | Two storeys, per m² | 40 m² two-storey with an en-suite, all in |
|---|---|---|---|
| Carlow | €1,600 to €2,200 | €2,150 to €2,500 | €109,000 to €128,000 |
| Cavan | €1,400 to €2,000 | €1,850 to €2,250 | €97,000 to €118,000 |
| Clare | €1,500 to €2,100 | €2,000 to €2,400 | €103,000 to €124,000 |
| Cork | €1,500 to €2,100 | €2,000 to €2,400 | €103,000 to €124,000 |
| Donegal | €1,400 to €2,000 | €1,850 to €2,250 | €97,000 to €118,000 |
| Dublin | €1,800 to €2,500 | €2,200 to €2,800 | €115,000 to €140,000 |
| Galway | €1,400 to €2,000 | €1,850 to €2,250 | €97,000 to €118,000 |
| Kerry | €1,500 to €2,100 | €2,000 to €2,400 | €103,000 to €124,000 |
| Kildare | €1,800 to €2,500 | €2,200 to €2,800 | €115,000 to €140,000 |
| Kilkenny | €1,600 to €2,200 | €2,150 to €2,500 | €109,000 to €128,000 |
| Laois | €1,600 to €2,200 | €2,150 to €2,500 | €109,000 to €128,000 |
| Leitrim | €1,400 to €2,000 | €1,850 to €2,250 | €97,000 to €118,000 |
| Limerick | €1,500 to €2,100 | €2,000 to €2,400 | €103,000 to €124,000 |
| Longford | €1,600 to €2,200 | €2,150 to €2,500 | €109,000 to €128,000 |
| Louth | €1,600 to €2,200 | €2,150 to €2,500 | €109,000 to €128,000 |
| Mayo | €1,400 to €2,000 | €1,850 to €2,250 | €97,000 to €118,000 |
| Meath | €1,800 to €2,500 | €2,200 to €2,800 | €115,000 to €140,000 |
| Monaghan | €1,400 to €2,000 | €1,850 to €2,250 | €97,000 to €118,000 |
| Offaly | €1,600 to €2,200 | €2,150 to €2,500 | €109,000 to €128,000 |
| Roscommon | €1,400 to €2,000 | €1,850 to €2,250 | €97,000 to €118,000 |
| Sligo | €1,400 to €2,000 | €1,850 to €2,250 | €97,000 to €118,000 |
| Tipperary | €1,500 to €2,100 | €2,000 to €2,400 | €103,000 to €124,000 |
| Waterford | €1,500 to €2,100 | €2,000 to €2,400 | €103,000 to €124,000 |
| Westmeath | €1,600 to €2,200 | €2,150 to €2,500 | €109,000 to €128,000 |
| Wexford | €1,600 to €2,200 | €2,150 to €2,500 | €109,000 to €128,000 |
| Wicklow | €1,800 to €2,500 | €2,200 to €2,800 | €115,000 to €140,000 |
| Waterford | €1,500 to €2,100 | €2,000 to €2,400 | €103,000 to €124,000 |
| Donegal | €1,400 to €2,000 | €1,850 to €2,250 | €97,000 to €118,000 |
All in covers the build, the drawings, the engineer, the BER and the en-suite fit-out, with VAT. Keep 12% to 15% on top for surprises.
Reading the rates
One storey: €1,500 to €2,200 per m²
The rate is for new rooms finished and working: the dig and foundations, an insulated floor slab, walls, roof, windows and outside doors, plaster, wiring, plumbing and heating, all to current building regulations. A standard finish lands in the lower half of the range and mid-range in the upper half. Dublin runs €1,800 to €2,500.
Two storeys: €2,000 to €2,500 per m²
Measure both floors. The foundations and the roof are among the dearest parts of any extension, and here they carry twice the floor area, so each m² costs less than on one level. The new bedroom usually opens off the landing you already have.
Fees: €5,000 to €10,000
For the drawings (an architect, an architectural technician or an engineer), the structural design, and a BER on the finished house. Expect the top of the range with a planning application, or where certifiers are needed above 45 m².
On top of the rate
The steel beam where the extension opens into the house (€2,000 to €4,000 for the beam), en-suite fittings and tiling (€4,000 to €8,000 standard, €10,000 to €18,000 mid-range, €20,000 to €40,000 high-end), a kitchen if one is going in, furniture, and the garden put back afterwards.
Garage conversions: €15,000 to €45,000
One price for the whole conversion, because the walls and roof stand already: €15,000 to €25,000 at a standard finish, €20,000 to €30,000 mid-range, €30,000 to €45,000 high spec or with an en-suite. Garage conversions.
Where the money goes further
- Go up rather than out. Per m², a second storey costs less than any other new space, because it shares the foundations and the roof.
- Look at the garage first. An attached garage converts for €15,000 to €30,000 at a standard to mid-range finish, usually with no planning application.
- Keep the back extension to 45 m² or less. No planning application or planning fees, and no certifiers under building control.
- Put new bathrooms over or beside the old one. They share the soil pipe, and nobody digs up a floor for new drains.
- Finish the drawings before you look for prices. A change made after the builder starts costs more than the same change on paper.
Questions before you build
What does a house extension cost per m² in Ireland?
€1,500 to €2,200 on one level and €2,000 to €2,500 over two storeys, VAT included. In Dublin, €1,800 to €2,500 and €2,200 to €2,800.
How much is a two-storey extension?
About €105,000 to €128,000 all in for 40 m² at a mid-range finish with an en-suite upstairs, at national rates. Dublin and the commuter counties cost more.
What does it cost to add a bedroom?
In Galway, a 16 m² ground-floor bedroom with an en-suite at a standard finish comes to about €32,000 to €45,000 with fees. Upstairs, the bedroom is part of a two-storey extension. Bedroom extensions.
How much is a garage conversion?
€15,000 to €25,000 at a standard finish, €20,000 to €30,000 mid-range and €30,000 to €45,000 high spec or with an en-suite.
Do these prices include VAT?
Yes, at 13.5%, the rate for building work on a house. VAT on house extensions.
Why do quotes for the same extension differ?
Builders often price different jobs: one includes the steel or the en-suite fit-out, another leaves it out. Give them all one set of drawings and ask for each item, the fees and the VAT on its own line.
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