Velux home office, Dublin
20 m² rooflight conversion on a mid-terrace house built after 1970, no extras.
- Build cost
- €22,000 to €35,000
- Contingency
- €2,200 to €5,250
Total budget
€24,000 to €40,000
Attic conversion cost calculator Ireland
A realistic budget for your attic conversion in about a minute, with 2026 prices for Dublin and the rest of Ireland. Includes VAT and a contingency.
- 5.0 on Google
- Prices updated November 2026
- Free, no sign-up
Your estimate€39,000 to €69,000See details
2026 prices
Attic conversion cost by type
These are the base project costs the calculator starts from, for a typical attic with 20 to 30 m² of usable floor space. They include labour, materials, a standard staircase and VAT at 13.5%. Dublin costs more because labour and site access cost more.
An attic conversion is priced as a project, not per m². The structure, staircase, fire protection and services cost much the same in a small attic as in a large one, so a small conversion is not simply a fraction of the price of a bigger one.
| Conversion type | Dublin | Rest of Ireland |
|---|---|---|
| Rooflight (Velux) | €22,000 to €35,000 | €18,000 to €30,000 |
| Dormer | €35,000 to €60,000 | €28,000 to €48,000 |
| Hip-to-gable | €48,000 to €75,000 | €40,000 to €65,000 |
| Mansard | €65,000 to €110,000+ | €55,000 to €90,000+ |
Base project cost for 20 to 30 m² of usable floor space, including VAT. Contingency comes on top.
Size and extras
What changes the price
Floor area adjusts the base cost rather than multiplying it. The base covers 20 to 30 m². Otherwise it is 5% less under 20 m², 10% more from 31 to 40 m² and 20% more from 41 to 45 m².
The calculator adds a contingency of 10 to 15% for a house built in 1970 or later, and 15 to 20% for an older house, where hidden structural problems are more common once the roof is opened up. The extras below only count when you pick them.
| Extra | Cost |
|---|---|
| Standard en suite | €6,000 to €12,000 |
| High-spec or complex en suite | €12,000 to €20,000 |
| Bespoke or space-saving staircase | €3,000 to €8,000 |
| Moderate structural work: a steel beam, minor party wall works | €3,000 to €8,000 |
| Significant structural work: major steelwork, a complex roof | €8,000 to €15,000 |
| Planning, drawings and professional fees | €1,500 to €5,000 |
Including VAT. The same figures apply in Dublin and the rest of Ireland.
Examples
Three example budgets
Three common attic conversions run through the calculator. These are Build Me estimates to show how the numbers add up, not prices from finished jobs.
Dormer bedroom with en suite, Dublin
30 m² rear dormer on a semi-detached house built after 1970, with a standard en suite.
- Build cost
- €35,000 to €60,000
- Standard en suite
- €6,000 to €12,000
- Contingency
- €4,100 to €10,800
Total budget
€45,000 to €83,000
Hip-to-gable, outside Dublin
35 m² hip-to-gable on a 1960s semi-detached house, with a standard en suite, moderate structural work and planning.
- Build cost
- €44,000 to €71,500
- Standard en suite
- €6,000 to €12,000
- Moderate structural work
- €3,000 to €8,000
- Planning, drawings and fees
- €1,500 to €5,000
- Contingency
- €8,175 to €19,300
Total budget
€63,000 to €116,000
Read the small print
What the estimate includes
Included
- ✓Structural work and a standard staircase
- ✓Insulation and airtightness
- ✓Electrics and lighting
- ✓Windows, rooflights and ventilation
- ✓Finishing and fit-out
- ✓VAT at 13.5% on the construction work
- ✓A contingency of 10 to 15%, or 15 to 20% for a house built before 1970, shown on its own
Not included
- –Planning, drawings and professional fees, unless you tick them
- –Furniture, blinds and soft furnishings
- –Work to the rest of the house that isn't part of the conversion
Optional extras the calculator can add: an en suite (€6,000 to €12,000, or €12,000 to €20,000 for high spec), a bespoke staircase (€3,000 to €8,000), extra structural work (€3,000 to €8,000, or €8,000 to €15,000 for major steelwork) and planning with drawings and fees (€1,500 to €5,000).
Do you need planning permission?
Under the 2026 exempted development regulations (S.I. 338 to 344 of 2026), side and rear dormers are exempt (Class 1B) if all the dormers on the house together add no more than 30 m³ of internal volume, stay below the ridge and sit at least 20 cm back from the eaves. Rear rooflights are generally exempt, and up to two front rooflights of up to 100 cm × 90 cm each are exempt (Class 1C).
Front dormers, hip-to-gable and mansard conversions, and raising the ridge, still need planning permission, as do protected structures and some homes in an Architectural Conservation Area. If yours does, tick “Planning, drawings and fees” in the calculator, and allow 12 to 16 weeks from drawings to a decision. Our attic conversion regulations guide covers planning and Building Regulations in detail.
How the calculator works
It starts from a base project cost for your conversion type and location, then adjusts it for floor area: 5% less under 20 m², 10% more from 31 to 40 m² and 20% more from 41 to 45 m². It doesn't multiply a per m² rate, because the fixed costs of an attic conversion don't shrink with the floor area.
An en suite, a bespoke staircase, extra structural work and planning only count when you pick them. The contingency is worked out on the build cost and extras together, and is higher for a house built before 1970, so you can see exactly what moves the number.
From an estimate to a fixed quote
An online estimate gets your budget right. A visit gets the price right, because the details that change a price only show up on site.
- 01
Get your estimate
Use the calculator to set a realistic budget before you speak to anyone.
- 02
Free call-out
We visit, look at the house and talk through what you want.
- 03
Written quote
A detailed quote in writing, with materials and every trade listed.
- 04
One team does the work
Managed by one team from start to finish.
Frequently asked questions
Still have questions about your attic conversion? Call 01 270 9764 and we’ll be happy to help.
How accurate is this attic conversion calculator?
It gives a realistic budget range from current Irish prices and your answers, not a fixed price. The roof structure, the state of the existing joists and access can all shift the final figure, so a written quote after a visit to your home is the only accurate figure for your project.
How much does a dormer attic conversion cost in Dublin?
For a typical 20 to 30 m² attic in Dublin, a dormer conversion costs €35,000 to €60,000 including VAT. With a 10 to 15% contingency, budget about €39,000 to €69,000 for a house built after 1970. A standard en suite adds €6,000 to €12,000. Outside Dublin, a dormer costs €28,000 to €48,000.
Is a Velux conversion cheaper than a dormer?
Yes. A rooflight (Velux) conversion costs €22,000 to €35,000 in Dublin, against €35,000 to €60,000 for a dormer, for 20 to 30 m² including VAT. A rooflight conversion keeps the roof shape, so it needs more existing headroom. A dormer adds headroom and usable floor space. Our Velux vs dormer guide compares the two in detail.
Does the calculator include planning permission costs?
It can. Planning, drawings and professional fees (€1,500 to €5,000) are off by default, so tick them if your design needs permission. Under the 2026 exempted development regulations, rear rooflights, up to two front rooflights (Class 1C) and side or rear dormers within 30 m³ (Class 1B) are usually exempt. Front dormers, hip-to-gable and mansard conversions need planning permission.
How long does an attic conversion take?
On site, a rooflight conversion typically takes 6 to 8 weeks and a dormer 8 to 10 weeks. Add about 2 weeks for an en suite. If you need planning permission, allow 12 to 16 weeks from drawings to a decision before work can start.
Is VAT included in the estimate?
Yes. All figures include VAT at 13.5%, which applies to construction work in Ireland.
Does the calculator account for my roof type?
Indirectly. Roof pitch decides which conversion types are realistic for your house. A rooflight conversion needs more existing headroom than a dormer or hip-to-gable conversion, so choose the type that matches what your roof can take. Our guide on where to start with an attic conversion explains how to check this.
What's not included in this estimate?
The calculator covers structural work and a standard staircase, insulation, electrics, windows and finishing, plus an en suite, a bespoke staircase, extra structural work and planning when you pick them. It doesn't include furniture, or any work to the rest of the house that isn't part of the conversion itself.