House Extension Cost Ireland 2026: What You'll Really Pay

A house extension in Ireland in 2026 will cost you between €1,900 and €3,400 per square metre, depending on what you're building and where you're building it. That's the headline. But if you're like most homeowners, you need more than a headline — you need to understand what drives those numbers so you can actually plan a budget that won't fall apart halfway through the build.

Before you go any further, you can get a free estimate at BeforeYouBuild.ie — it takes 60 seconds and gives you a county-specific cost range before you talk to any builder.

What Type of Extension Are You Planning?

The type of extension you're building is the single biggest factor in what you'll pay. Here's how the main types stack up in 2026:

Single-storey rear extension is the most common type in Ireland. You're extending the back of the house, usually to create a bigger kitchen, an open-plan kitchen-living area, or a new living room. For a standard finish, expect to pay around €1,900 to €2,500 per square metre. For a high-spec finish with underfloor heating, large-format tiles, and big sliding doors, you're looking at €2,500 to €3,000 per square metre.

Single-storey side extension uses the space along the side of your house. These can be slightly cheaper than rear extensions because the roof structure is often simpler, but you'll almost certainly need planning permission. Budget €1,800 to €2,400 per square metre.

Two-storey extension gives you the most space for your money. You're already paying for foundations and a roof — adding a second storey on top shares those fixed costs across a larger floor area. Standard finish runs €2,000 to €2,500 per square metre, while high-spec builds can reach €2,600 to €3,400 per square metre.

Wrap-around extension combines rear and side, giving you the maximum space gain. It's the most expensive type overall but often the best value per square metre for larger projects. Expect €2,200 to €3,200 per square metre.

What Does That Look Like in Real Money?

The per-square-metre figure is useful for comparison, but what matters is the total cost landing on your kitchen table. Here are some real-world examples:

A 20m² rear kitchen extension at mid-spec will cost roughly €45,000 to €55,000 including VAT at 13.5%. Add planning and design fees, and you're at €52,000 to €63,000 all in.

A 30m² rear extension — the most popular size — will typically cost €60,000 to €85,000 including VAT. With professional fees, budget €70,000 to €95,000.

A 40m² two-storey extension (so 80m² total floor area) at standard spec comes in around €160,000 to €200,000 including VAT and fees. This gives you a new kitchen-living space downstairs and two bedrooms upstairs.

A 50m² wrap-around at mid-to-high spec can reach €130,000 to €170,000 including VAT, before you add fees.

These figures include materials, labour, and VAT at 13.5%. They do not include planning permission, architect/engineer fees, or your new kitchen units and appliances.

The Costs That Catch People Out

Every homeowner we've spoken to says the same thing: the extension itself was the easy bit to budget for. It's everything else that caught them off guard.

Professional fees are the first one. You'll need an architect or architectural technologist to draw up plans (€3,000 to €8,000 depending on complexity), a structural engineer for calculations (€1,500 to €3,000), and a building energy rating (BER) assessment (€150 to €350). For a typical extension, budget €5,000 to €10,000 in professional fees on top of the build cost.

Planning permission costs €34 to apply, but the real cost is the architect's time to prepare the drawings and reports to the standard the planning authority requires. If you need planning (anything over 40m² to the rear, anything to the side, any two-storey work), the full planning package typically costs €2,000 to €5,000.

Temporary living arrangements are something nobody thinks about. If your kitchen is being ripped out and rebuilt, you could be without a working kitchen for 8 to 16 weeks. That's a lot of takeaways, or the cost of a temporary kitchen setup.

Services diversions can add thousands. If a drain, gas line, or ESB cable runs under where you want to build, it needs to be moved before work starts. ESB diversions alone can cost €1,500 to €3,000.

Making good is the work to patch up where the new extension meets the existing house — matching render, repainting, fixing the garden after the digger has been through it. Budget €2,000 to €5,000.

Skip hire and waste runs €300 to €500 per skip, and most extensions need three to five skips over the course of the build.

Why Dublin Costs More

If you're building in Dublin, add 10% to 20% to the figures above. Dublin extensions tend to cost more for three reasons: labour rates are higher because demand for tradespeople outstrips supply, access to sites is often tighter (terraced houses, narrow side passages), and material delivery is more expensive in the city due to traffic and parking restrictions.

In rural areas, particularly in the northwest, costs can be 10% to 15% lower — but you may face longer wait times to get a builder started because there are fewer contractors available.

Your county matters. BeforeYouBuild.ie uses county-specific pricing in every estimate, so the number you get reflects where you're actually building.

How to Budget Without Losing Your Mind

Here's the approach we'd recommend:

Step 1: Get a ballpark estimate. Use BeforeYouBuild.ie to get a county-specific cost range in under a minute. This gives you a realistic starting point before you talk to anyone.

Step 2: Talk to an architect. Even a one-hour consultation (€150 to €300) can save you thousands by identifying the most cost-effective way to get the space you need.

Step 3: Get three quotes. Never accept the first quote. Get at least three written quotes that break down the cost by trade (groundworks, structural, roofing, plumbing, electrical, finishes). This lets you compare like with like. And you can compare with our Detailed Cost Report to see how it stacks against industry standards.

Step 4: Add 10% to 15% contingency. Every build has surprises — unexpected ground conditions, a wall that's not where the drawings said it was, a material that's gone up in price since the quote. A contingency fund means these surprises don't derail your project.

Step 5: Lock in prices early. Ask your builder to hold material prices for the duration of the build. If they can't, make sure the quote includes an allowance for material price increases.

Ready to Get Started?

The first step is knowing what you're looking at. Try the free estimate on BeforeYouBuild.ie — it takes 60 seconds and gives you a county-specific cost range before you talk to any builder. No signup needed for your first estimate.

*BeforeYouBuild.ie helps Irish homeowners understand construction costs before they commit. Our calculator uses county-specific pricing data to give you a realistic ballpark estimate for new builds, extensions, and renovations across Ireland.*