You need more space. The question is: do you go up — with an attic conversion — or out — with a rear extension? Both are popular choices in Dublin, but they're very different in terms of cost, disruption, planning and return on investment.
Here's a straight comparison to help you decide.
Cost Comparison
| Project | Typical Cost Dublin 2026 |
|---|---|
| Attic conversion (dormer) | €25,000 – €40,000 |
| Single storey rear extension | €40,000 – €70,000 |
| Two storey rear extension | €70,000 – €120,000 |
| Side extension | €35,000 – €60,000 |
💡 An attic conversion is typically 40–60% cheaper than an equivalent rear extension for the same amount of usable floor space.
Value Added to Your Property
| Project | Typical Value Added |
|---|---|
| Attic conversion (dormer with en-suite) | €50,000 – €80,000 |
| Single storey rear extension | €30,000 – €60,000 |
| Two storey rear extension | €60,000 – €100,000 |
🏆 Winner on ROI: Attic Conversion
An attic conversion typically delivers the highest return on investment of any home improvement in Dublin — adding more value per euro spent than most extensions.
Planning Permission
Attic Conversion
Most attic conversions in Dublin are exempt from planning permission under exempted development rules, provided the conversion is to the rear and under 40 sq metres.
House Extension
Single storey rear extensions up to 40 sq metres are also generally exempt. However, extensions that exceed this, affect the front of the property, or are in conservation areas will need full planning permission — which adds cost and time.
Disruption During Build
Attic Conversion
Work is done primarily from above. The main disruption is the installation of the staircase and the temporary opening in the roof. Most families stay in the house throughout. Typically 6–10 weeks.
Extension
More disruptive — particularly if it involves the kitchen or living areas. You may need to relocate temporarily during certain phases. Typically 12–20 weeks.
Which Should You Choose?
Choose an attic conversion if:
- You need a bedroom, en-suite or home office
- You want the best return on investment
- You want minimal disruption to daily life
- Budget is a consideration
Choose an extension if:
- You need to expand your kitchen or living space
- You want an open-plan ground floor layout
- You need a large family room or playroom
Many Dublin homeowners do both over time — starting with an attic conversion for the bedroom, then adding an extension later for the kitchen. It's a very common sequence.
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