How much does a house extension cost in Ireland?
2 Mar 2026
Thinking about extending your home? You're not alone. With rising property prices and a shortage of housing across Ireland, more homeowners are choosing house extensions over moving to a larger house. But before you start planning your house extension, you need to know how much does a house extension cost in Ireland?
In this guide, we break down the real cost of house extensions in Ireland including build costs per square metre, what factors affect your budget and what to watch out for when hiring a contractor.
Average House Extension Cost in Ireland
As a general rule of thumb, house extensions in Ireland typically cost between €1,500 and €3,000+ per square metre, depending on the type of extension, finish level, and location.
Here's a quick overview of typical costs:
Extension Type | Estimated Cost (per m²) | Typical Total Cost |
Single-storey | €1,500 – €2,000/m² | €30,000 – €60,000 |
Double-storey | €1,800 – €2,500/m² | €60,000 – €120,000 |
Side extension | €1,500 – €2,200/m² | €25,000 – €55,000 |
Kitchen Extension | €1900 – €3000/m² | €36,00 – €50,000 |
What Factors Affect the Cost of a House Extension in Ireland?
There are several key factors that can determine the cost of your house extension.
1. Size of the Extension
The larger the extension, the higher the overall cost. This is because a larger extension requires more labour, materials, planning and design.
2. Location in Ireland
Build costs in Dublin tend to be 10–20% higher than in rural areas or smaller towns, due to higher labour costs and demand. Extensions in Cork, Galway, and Limerick city centres also tend to command a premium.
3. Ground Conditions & Structural Work
If your site has poor ground conditions, high water tables, requires significant excavation, knocking through walls, relocating utilities or reinforcing existing structures, then you can expect costs to rise quickly. A preliminary site investigation can help identify this early.
4. Specification & Finish Level
The finish you choose from flooring and windows to kitchen fittings and insulation levels can dramatically affect the final cost. A standard finish costs considerably less than a high-spec finish.
Cost Example: Single-Storey Rear Extension
For a typical 20m² single-storey extension in Ireland, you might expect to pay:
Standard finsh: €30,000 – €40,000
High-spec finish: €55,000 – €80,000+
Cost Example: Double-Storey Extension
For a typical 40m² double-storey extension in Ireland, you might expect to pay:
Standard finsh: €72,000 – €100,000
High-spec finish: €110,000+
Cost Example: Kitchen Extension
A kitchen extension will typically cost €36,000 - €50,000
Do I Need Planning Permission for a House Extension in Ireland?
Under Irish planning regulations, many extensions qualify as exempt development, meaning you don't need to apply for full planning permission provided they meet certain conditions. Key exemption rules include:
Extensions to the rear of a house are generally exempt up to 40m² (or 12m² at the side), subject to conditions.
The extension must not exceed the height of the original house.
Certain boundary and overlooking conditions must be met.
Even if your project is exempt, you may still need to demonstrate compliance with building regulations. Always consult with a qualified architect or contractor before proceeding.
How to Keep Costs Under Control
Getting a house extension right, on time and on budget comes down to careful planning and choosing the right team. Here are some practical tips:
Get detailed quotes. A reputable contractor will provide a detailed, itemised quote rather than a vague estimate. This makes it far easier to compare like with like.
Decide on your specification before you start. Changing your mind mid-build is one of the most common causes of cost overruns. Make all your decisions on windows, flooring, kitchen layout before work begins.
Choose a contractor with a solid track record. Look for builders who can provide references, examples of similar past work to ensure the extension will be completed without delay.
How Much Value Does a House Extension Add?
In most cases, a well designed and well built extension adds more value to your home than it costs to build. Research consistently shows that extending a property can increase its value by 10–25%, depending on location and the type of extension.
In a city like Dublin, where every square metre of living space is at a premium, the return on investment from a quality extension can be substantial.
Why Choose a Local, Experienced Building Contractor?
A house extension is one of the biggest investments you'll make in your home. Choosing the right contractor makes all the difference not just to the final result but to your experience throughout the build.
At Joseph Barrett Contractors, we've delivered many house extensions for homeowners just like you. From initial design advice and planning applications through to the finishing touches, we manage the entire process keeping you informed at every step.
We provide detailed, transparent quotes with no hidden costs, and every project is backed by our commitment to quality workmanship and timely delivery. Call now for a free quote.