How Much Does a House Extension Cost in Dublin in 2026?
Planning a house extension cost Dublin project? You're asking the right question. Extension costs have shifted significantly in 2026, and understanding the breakdown is crucial to budgeting effectively. With over 35 years of building experience in Ballinteer and South Dublin, BR Building Services has completed hundreds of extensions, and we're here to give you realistic pricing that helps you plan with confidence.
Whether you're considering a single-storey rear extension, a two-storey addition, or a side return, this comprehensive guide covers all the factors that affect pricing in Dublin's current market.
Current House Extension Costs in Dublin (2026)
The cost per square metre is the best way to compare extension pricing across Dublin. Here's what you can expect in 2026:
| Extension Type | Cost Per m² | Typical Size | Total Cost Range |
|---|---|---|---|
| Single Storey Rear | €1,800 - €2,500 | 20-40 m² | €36,000 - €100,000 |
| Two-Storey Extension | €2,200 - €3,000 | 30-50 m² | €66,000 - €150,000 |
| Side Return Extension | €1,900 - €2,600 | 15-25 m² | €28,500 - €65,000 |
| Wraparound Extension | €2,100 - €2,800 | 40-80 m² | €84,000 - €224,000 |
Key Insight
These costs include structural works, labour, materials, basic finishes, and contingency. They do not include planning applications, engineering fees, or site clearance. Always budget an additional 10-15% for unforeseen issues.
What Drives House Extension Costs Up?
1. Foundation and Ground Conditions
Poor soil conditions, high water tables, or existing underground services can significantly increase costs. South Dublin properties, especially near streams or with clay soil, often require deeper foundations or piling work. Ground investigations can cost €2,000-€5,000 but save headaches later.
2. Specification and Finishes
A budget extension with standard blockwork, basic windows, and simple plasterboard finishes costs substantially less than a premium specification with high-performance glazing, acoustic insulation, and designer finishes. The difference: €500-€1,000 per square metre.
3. Access and Site Conditions
Tight access with no side passage, narrow gardens, or neighbours' trees mean slower, more expensive work. A property in Ballinteer's semi-detached housing may have different constraints than a detached home, affecting labour costs by 15-25%.
4. Planning and Building Control
Extensions larger than 40 m² or two-storeys typically need planning permission (€500-€1,500 application fee, plus potential consultant fees). Building Control registration and inspection fees add €1,000-€2,000. Some extensions qualify for exemption under Part 4 of the Building Regulations.
5. Existing Building Condition
If your Dublin home has structural issues, asbestos, or requires remedial works, costs escalate. Discovering damp, woodworm, or weak cavity ties during construction can add €5,000-€20,000.
6. Connecting to Services
Relocating utilities (water, drainage, electrics, gas) to accommodate an extension adds cost. Connecting to existing HVAC systems or upgrading electrical capacity can be expensive if the main installation is old or undersized.
What Can Actually Save You Money?
Standard Specification Materials
Using tried-and-tested products rather than bespoke or high-end alternatives keeps costs down. Standard cavity block, white PVC windows, and plasterboard finishes are cost-effective and perform well.
Simple Geometric Design
A rectangular single-storey rear extension costs less to build than an L-shaped or angled design. Complex roof lines, multiple levels, or special features increase labour time and material waste.
Off-Peak Construction
Building in autumn or winter may yield 5-10% cost reductions as contractor availability increases and material suppliers run promotions.
Flexible Timeline
If you can wait for labour availability or material deliveries rather than demanding urgent completion, negotiation room exists. Emergency timelines add costs.
Breaking Down the Costs
For a typical 25 m² single-storey rear extension in Dublin at €2,000/m², the €50,000 budget breaks down roughly as:
- Structural Materials (35%): €17,500 - brickwork, blockwork, concrete, steel lintels
- Labour (40%): €20,000 - skilled tradespeople (bricklayers, carpenters, electricians, plumbers)
- Finishes & Fittings (15%): €7,500 - windows, doors, flooring, paint, plasterboard
- Contingency & Overhead (10%): €5,000 - unforeseen issues, site costs, profit margin
Labour typically represents 35-45% of extension costs. Dublin's construction skills shortage has kept wages competitive (€25-€45 per hour for skilled trades), so this hasn't dropped since 2025.
Planning and Regulation Costs
Don't overlook the "hidden" costs beyond construction:
- Planning Application: €500-€1,500
- Structural Engineering Design: €1,500-€3,500
- Building Control Registration & Inspection: €1,000-€2,000
- Legal/Conveyancing (if required): €500-€1,000
- Temporary Protection/Scaffolding: €2,000-€5,000
Total "soft costs" can reach 8-12% of the construction budget.
Timeline and Cost Implications
A typical single-storey extension takes 12-16 weeks from excavation to completion. Two-storey extensions require 18-24 weeks. Weather, supply chain delays, and Building Control inspection scheduling all affect timelines and costs.
Every week of delay costs approximately €500-€1,500 in site overheads, labour remobilisation, and potential contract renegotiations.
Why BR Building Services Delivers Value
With 35+ years building houses and extensions across Dublin 16, Ballinteer, and South Dublin, we've perfected the process. We:
- Maintain relationships with reliable suppliers, reducing material costs
- Use tested methods that minimize waste and rework
- Have in-house teams, reducing subcontractor markups
- Understand Dublin's Building Control and planning process intimately
- Provide transparent quotes with no hidden surprises
Our clients consistently report on-time, on-budget delivery, and extensions that add significant value to their homes.
Getting Your House Extension Quote
Don't rely on generic online calculators. Every property is unique. Ground conditions, access, existing structure, and your specification drive costs. A detailed site survey and specification brief are essential for accurate pricing.
We offer comprehensive extension services, from initial survey through practical completion. Our quotes are based on real site data, not assumptions.