House extensions in Carlow
In Carlow, building a house extension costs €1,600 to €2,200 per m² for one storey and €2,150 to €2,500 per m² for two, VAT included. With fees, a 20 m² ground-floor room comes to €43,000 to €54,000 and a 40 m² two-storey extension with an en-suite upstairs to €109,000 to €128,000. Behind the house, 45 m² can go on without a planning application if the conditions are met.
For homes in Carlow Town, Graiguecullen, Tullow, Bagenalstown (Muine Bheag), Leighlinbridge and Borris: the cost of extending, the county's housing, its council, and the price of moving instead.
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- €1,600–€2,200per m², one storey in Carlow, VAT in
- €2,150–€2,500per m², two storeys
- 60%of Carlow houses have three bedrooms or fewer
- €265,000median paid by movers in Carlow, 2025
Extending a house in Carlow
In Carlow, 60% of houses have three bedrooms or fewer and 40% have four or more, across 20,624 permanent houses in the county (Census 2022). The average detached house has 3.6 bedrooms and the average semi 3.1.
People moving home in Carlow paid a median of €265,000 in 2025, across 241 sales (CSO). Selling at that price and buying another costs €8,000 to €16,000 in stamp duty, the estate agent's fee with VAT and the solicitor before the higher price of a bigger house.
46% of Carlow houses have exactly three bedrooms. Adding a single-storey family room at the back, converting an attached garage, or building a ground-floor or two-storey bedroom extension keeps the house you know without the dead costs of moving.
Carlow is priced in the rest of Leinster: €1,600 to €2,200 per m² for one storey and €2,150 to €2,500 for two, VAT included. Planning applications and €80 section 5 exemption declarations go to Carlow County Council.
- 46%of houses have exactly three bedrooms
- 40%have four or more
- 3.1bedrooms in the average semi
- 20,624houses in Carlow (Census 2022)
What an extension costs in Carlow
| Extension | Per m² in Carlow, VAT in | Example, all in |
|---|---|---|
| One storey behind the house | €1,600–€2,200 | 20 m², mid-range: €43,000 to €54,000 |
| Ground-floor bedroom with an en-suite | €1,600–€2,200 | 16 m², standard finish: €35,000 to €49,000 |
| Two storeys, both floors counted | €2,150–€2,500 | 40 m² with an en-suite upstairs: €109,000 to €128,000 |
| Side extension | €1,900–€2,400 | 15 m², mid-range: €38,000 to €46,000 |
| Wraparound | €2,350–€3,200 | 40 m², mid-range: €117,000 to €138,000 |
| Mostly glass, or high spec | €3,000–€3,500 | 20 m² with a wall of glass: €65,000 to €80,000 |
| Garage conversion | One price for the job | €15,000–€45,000 |
Every example includes the build, the drawings and engineer's fees, any en-suite and VAT. Set aside 12% to 15% more for surprises.
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 in Carlow, mid-range finish: €53,000 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.
Extend or move in Carlow
On a €265,000 house, the median people moving home in Carlow paid in 2025, stamp duty on the next house is €2,650, the agent's fee on the sale €3,300 to €8,100 with VAT, and the solicitor €2,000 to €5,000. That is €8,000 to €16,000 spent before the bigger house's higher price, against €43,000 to €54,000 to build a 20 m² room here. Extend or move house has every county side by side.
Planning in Carlow
Planning rules don't change at the county line. Since 27 July 2026, 45 m² behind the house is exempt if it meets the conditions, and converting an attached garage shares that 45 m². Building at the side, and most two-storey extensions, need an application. In Carlow you apply to Carlow County Council: €34 for an extension, or €80 for a section 5 declaration on whether your plan is exempt.
Three things can take the exemption away. A condition in the planning permission your house was built under can remove it, and newer estates often have one. On a protected structure, work that would affect its character isn't exempt. And no extension is exempt if it would obstruct a public right of way or create a traffic hazard. Planning permission for a house extension.
Every way to extend a Carlow house
Each has its own page: costs by size, the planning rules that apply and the weeks of building.
Single-storey rearOne new room behind the house at ground level: a family room, a playroom or a bedroom for a parent.
Two-storeyTwo new floors in one build: more living space downstairs and an extra bedroom over it.
Side extensionThe strip beside a semi or detached house, built on at one level or two.
WraparoundAn L round the back corner of the house, for one big room with a utility or toilet off it.
Garage conversionThe garage you already have becomes a bedroom, an office or a playroom.
Bedroom and en-suiteOne more bedroom, downstairs or up, with a shower room of its own.House Extension coverage across every town in Co. Carlow
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Select your town, suburb or Eircode routing area in Co. Carlow below to pre-fill your location and open our quick 30-second quote check:
Local house extension coverage across Co. Carlow includes Carlow Town, Graiguecullen, Tullow, Bagenalstown (Muine Bheag), Leighlinbridge, Borris, Hacketstown, Rathvilly, as well as Ballon, Myshall, Fenagh, Tinryland and surrounding rural townlands.
Carlow questions
What does a house extension cost in Carlow?
In Carlow, building a house extension costs €1,600 to €2,200 per m² for one storey and €2,150 to €2,500 per m² for two, VAT included. With fees, a 20 m² ground-floor room comes to €43,000 to €54,000 and a 40 m² two-storey extension with an en-suite upstairs to €109,000 to €128,000. Behind the house, 45 m² can go on without a planning application if the conditions are met.
Does an extension in Carlow need planning permission?
Since 27 July 2026 you can build up to 45 m² behind the house without applying for planning permission. That 45 m² includes every extension added since 1964 and any attached garage you convert. The extension can't rise above the house, the house has to keep 25 m² of private open space, ground-floor windows need 1 m or more to the boundary they look onto, and no more than 12 m² of it can be upstairs on a semi or terrace (20 m² on a detached house). Before that date the limit was 40 m². Applications go to Carlow County Council.
Is it cheaper to extend or move in Carlow?
Moving on the Carlow median of €265,000 costs €8,000 to €16,000 in stamp duty, agent's and legal fees before the bigger house's price. A 20 m² room costs €43,000 to €54,000 to build here.
Which parts of Carlow do you cover?
All of it, including Carlow Town, Graiguecullen, Tullow, Bagenalstown (Muine Bheag), Leighlinbridge and Borris. Your plan goes to a single vetted builder who works in Carlow.
Who will contact me?
One builder who works in Carlow and has been vetted, and only that one. They price the job in writing after seeing the house, and you decide.
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