Garage conversion or extension: which is right?
Converting the garage costs €20,000 to €30,000 at a mid-range finish. A 20 m² single-storey extension at the back, with drawings and engineer's fees, comes to €42,000 to €54,000, roughly twice as much, because the foundations, walls and roof of a garage are already built.
What each costs, how long each takes, and what you give up, for the same extra room.
Free and no obligation. Your plan goes to one builder, not a list.
- €20,000–€30,000a mid-range garage conversion
- €42,000–€54,000a 20 m² extension with fees
- 6–10 weekson site for the garage
- 45 m²exempt limit both share
Side by side
| Garage conversion | Single-storey extension | |
|---|---|---|
| Cost for a room | €20,000–€30,000 (mid-range, single garage) | €42,000–€54,000 (20 m², mid-range, with fees) |
| Weeks on site | 6 to 10 | 8 to 14, after 8 to 16 for drawings and prices |
| Planning | Exempt if attached at the side or back | Exempt behind the house up to 45 m², if the conditions are met |
| What you lose | Parking and storage | Garden |
| Room size | Fixed by the garage, about 15 to 18 m² for a single | Whatever you design, within the rules |
| Disruption | Mostly inside the garage | Digging, foundations and a new roof at the back |
Both figures include VAT at 13.5%. The extension is priced at national rates for a mid-range finish with drawings, engineer's and BER fees. Keep 12% to 15% aside for either.
Plan your garage conversion
Four quick taps, and your plan fills in as you answer: the cost in your county, the planning position for your kind of garage and how many weeks it takes. Contact details come last, and only if you want a builder to price it.
An attached garage made into a bedroom, mid-range finish: €20,000 to €30,000, including VAT.
How the estimate is worked out
A garage conversion is priced as one job, because the walls, roof and floor slab are already standing: insulating the floor, walls and roof, building up the door opening with a window, wiring, heating, plastering and the finish. The range for your finish is adjusted to your county the same way building rates move between regions of Ireland, VAT at 13.5% included. A shower room, a small kitchen or a steel beam into the house go on top. Totals are rounded to the nearest €1,000. Use it to plan with. It isn't a quote: a builder prices your garage after seeing it.
When the garage wins
- Money is the limit. For roughly half the price of a new room, the garage gives you one of a similar size.
- The room you need fits in it. A bedroom, an office, a playroom or a gym all fit a single garage.
- You want it soon. No foundations, no new roof structure, and usually no planning application.
- The garage holds bikes and boxes, not a car. If the car lives in the drive anyway, the garage is the least expensive space you have.
When an extension wins
- You need a bigger room. A kitchen with a living area, or a room for the whole family, needs more than 15 to 18 m².
- You need the garage. For a car, a workshop or storage there is nowhere else for.
- The garage is in poor shape. A cracked slab, a failed roof and single-leaf walls can cost close to new building.
- You want to do both. Converting the garage and extending behind it share the same 45 m² exemption, so plan them together. For extensions, houseextension.ie covers costs and planning in detail.
Doing both
If the garage becomes a bedroom and the back gets a family room, add the two floor areas together with any extension since 1964. Up to 45 m² in total can be exempt; above that, part of the plan needs permission. One set of drawings for both, and one builder pricing both, keeps it simpler.
Questions before you convert
Is a garage conversion cheaper than an extension?
Converting the garage costs €20,000 to €30,000 at a mid-range finish. A 20 m² single-storey extension at the back, with drawings and engineer's fees, comes to €42,000 to €54,000, roughly twice as much, because the foundations, walls and roof of a garage are already built.
Does a garage conversion add value?
It adds a room to the house, which buyers count. Whether it adds more than it costs depends on the area and on whether buyers there expect a garage.
Can I convert the garage and extend?
Yes. The two share the 45 m² Class 1 limit, along with any extension built since 1964.
Which is quicker?
The garage. 6 to 10 weeks on site, against 8 to 14 for a single-storey extension.
Every guide and county page
Conversions
Costs, rules and help
The room you need is already built
Pick the kind of garage, what it becomes and the finish to see the cost in your county. When you want a firm price, your plan goes to a single vetted builder for your area.