Thinking of expanding your home in Ireland? One of the first questions you’ll ask is: What is the house extension cost in Ireland? Whether you’re planning a single-storey rear extension, a two-storey side addition, or a loft conversion, understanding the true costs—both financial and practical—is essential.
With the cost of living, building materials, and labour steadily rising, homeowners must plan strategically. This guide provides detailed insights into current extension costs, budget planning, regulations, and how to make your project worthwhile.
Average House Extension Cost in Ireland (2025)
Cost Per Square Metre: The Basics
The typical house extension cost in Ireland ranges from:
- €1,900 to €2,300 per m² for a basic finish
- €2,500 to €3,000 per m² for a high-spec finish
These figures include materials, labour, and VAT but exclude planning permission and design fees. Prices vary depending on:
- Region (Dublin tends to be more expensive than rural areas)
- Access to the site
- Quality of materials
- Specialist features (e.g., underfloor heating or bespoke glazing)
Factors That Influence Extension Costs
1. Location
Labour and material costs differ by region. Urban centres like Dublin, Cork, and Galway command higher rates due to demand, congestion charges, and logistics. In contrast, rural areas may offer savings on tradespeople and suppliers but could incur transport fees for specific materials.
2. Size and Layout
Naturally, the bigger the extension, the more it will cost. However, economies of scale can apply; doubling your floor space doesn’t necessarily mean doubling your budget. Considerations include:
- Number of floors (single vs. double storey)
- Internal layout complexity
- Integration with the existing structure
3. Specification & Finish Quality
A standard finish might include laminate flooring, white PVC windows, and basic kitchen fittings. A high-spec finish could involve:
- Triple-glazed aluminium windows
- Premium tiling and flooring
- Bespoke kitchen cabinetry
- Designer lighting
Expect to pay an additional €300–€700 per m² for high-end finishes.
4. Structural Work
Any structural alteration—such as knocking down internal walls, underpinning foundations, or relocating load-bearing walls—will add to your overall costs. Structural engineers’ reports and reinforced steelwork may be required.
Extension Cost Examples
Single-Storey Rear Extension (20 m²)
- Standard Finish: €38,000 – €46,000
- High-End Finish: €50,000 – €60,000+
Two-Storey Side Extension (40 m²)
- Standard Finish: €76,000 – €92,000
- High-End Finish: €100,000 – €120,000+
Kitchen Extension with Interior Renovation
- Add €10,000 – €25,000 for integrated kitchen upgrades, new appliances, or open-plan redesigns.
Planning Permission & Regulations in Ireland
When Do You Need Planning Permission?
In Ireland, planning permission is not required for rear extensions up to:
- 40 m² for the entire extension
- Provided 25 m² of garden space remains
- The height does not exceed the main house
However, you’ll need permission if:
- The extension changes the front or side profile of the property
- You’re building a second storey
- You live in a listed or protected building
Building Regulations & Certification
Regardless of planning permission, all extensions must comply with Irish building regulations for fire safety, insulation, structural integrity, and ventilation.
A certificate of compliance from a registered architect or engineer will be essential when selling your home in the future.
Additional Costs to Consider
Aside from per-square-metre costs, homeowners should budget for:
Item | Estimated Cost |
Planning Permission Application | €65 – €300 |
Architect / Designer Fees | 8% – 12% of total build |
Structural Engineer Reports | €500 – €2,000 |
BER Assessment | €150 – €300 |
Utility Connections / Drainage | €2,000 – €6,000+ |
Temporary Accommodation (if needed) | €1,000 – €3,000+ |
How to Save Money on Your Extension
- Use a design-and-build firm to combine architecture and construction
- Avoid major structural changes unless necessary
- Plan utilities smartly to minimise plumbing/electrical rerouting
- Reuse existing space efficiently before expanding
- Get multiple quotes from reputable contractors
Do House Extensions Add Value in Ireland?
Yes—if designed well and built to a high standard, an extension can significantly boost your property’s market value. On average:
- A rear extension adds 10% – 15% to home value
- A kitchen or open-plan redesign can add more than €25,000
- An extra bedroom typically yields a 15%+ ROI
However, poor workmanship or awkward layouts can reduce appeal. Always consider your home’s overall flow and potential buyer expectations in your area.
Extension Alternatives That Also Add Value
If you’re not ready for a full extension, consider these space-enhancing options:
- Attic conversions: From €15,000 (non-habitable) or €25,000+ (habitable)
- Garage conversions: €12,000 – €30,000
- Bi-fold doors and patio redesigns: Enhance garden usability and light
Final Thoughts
House extensions in Ireland can transform how you live—and significantly increase your property’s value. While the costs can be substantial, smart planning, clear budgeting, and hiring trusted professionals can ensure a strong return on investment.
If you’re ready to begin your extension journey, make sure to get a detailed cost estimate, check for planning permission requirements, and align your vision with the right team.
Start building your dream home today—carefully, strategically, and with the right guidance.
OS Holding, one of Dublin’s leading construction companies, offers a full-service solution—from initial design through to flawless execution. With over a decade of experience in extensions, renovations, and new builds, our expert team ensures your project is completed efficiently, safely, and with minimal disruption.
Start building your dream home today with OS Holding—trusted, experienced, and fully committed to making your vision a reality. Contact us to get started.