Home Q&A: Garage conversions, modular buildings and cabins

For an attached garage, you may be able to add 40 detached square metres (presuming there are no other extensions, it’s the aggregated total). Further outbuildings, cabins or extensions would demand permission at present. 

Due to the housing crisis, the government is considering changes to the rules regarding habitable “cabins” craned in or constructed in family gardens. Could this impact the use of detached garages? Possibly. We don’t yet have the granular detail. 

In rural areas there is some leeway for larger buildings for agricultural uses; see planningpermissionireland.ie.

What about location?

There are some limitations here. The garage cannot be forward of the front wall of the house. This is generally fine for most homes, but there may be situations where you cannot manage to get it behind that line — so again, research planning before hitting the accelerator. 

When you build something as large as this, the finish should agree with the finish of the house — which makes sense. If you’re putting up a large steel shed, or anything off standard in terms of size and appearance, check it will fly with planning first (the area planning officer should be able to help here).

When the garage is finished it should not leave less than 25sq m of outdoor room. Always talk to your local authority before going ahead as some properties carry special conditions and covenants as part of their original planning permission. This can even interfere with usually exempted development.

What about boundary issues with a new garage?

There’s no limit here in terms of permission, so your garage could be right up against the boundary, but there are a couple of things to keep in mind. First of all, don’t place any window on the building facing into your neighbour’s property! 

Secondly, people can forget the overhangs and gutters of their new garage need room too — a small gap of a metre or so along the boundary will ensure nothing hangs over the property line into next door. 

If your garage is likely to impede your neighbour’s enjoyment of their garden — look into it. Detached steel sheds used as garages are not temporary structures. Over 25 sq m — go for planning.

What if I want to add a garage or modular building for residential use?

A popular hack for a working annexe, playroom or guest accommodation, residential use would not be covered by standard planning for a garage. However, the government has acknowledged that current housing policy may have to change to meet the moment. 

There is discussion around allowing small cabins and modular buildings to be used as residential units, together with a planning exemption for detached “extensions” under 40 sq metres. It’s still unclear if detached garages could be converted under these new rules. 

If you’re already using a detached garage as living space, take some professional advice if you’re planning to sell. You can’t fail a survey when selling (it could be ropey but there’s no failing per se), but planning problems and structural problems will be flagged.

Could you explain planning permission for converting an attached garages?

You can convert your attached garage to residential use (beyond a playroom or gym) if it’s under 40 sq m and you haven’t had other residential extensions. 

Attached garages can be a fantastic way to increase warm space, but if you have bigger ideas, like putting on a second storey, currently you will need planning. The garage should only be to the back or the side of the property and linked physically to the house. 

If you’re living in an estate of similar homes, see what other people in the area have achieved. Don’t take this as tacit permission to just roar ahead with the work. If you’re thinking of using a garage as room for a business, you must apply for permission for what’s termed “material change of use”. 

If you convert a garage to a self-contained annexe for an aged parent or student — that falls under material change of use (unless the law changes in the very near future — and it might).

How can I make my garage into a liveable space?

Unless the garage was detailed by a forward-thinking architect, engineer and/or contractor, the exterior walls are generally uninsulated and it’s detailed with a cold, concrete slab floor. 

The existing foundations may not support a second storey if that’s what you’re after. It won’t meet any of the safety and accessibility standards of the rest of your home. 

The height of the garage may make the prospect of living space difficult without raising the entire roof. Internal changes alone are an unlikely outcome. The walls will be changed to accommodate large windows, and the roof might include a roof light. 

External changes require planning. Is what amounts to a costly rebuild worth it? Looking at many suburban estates with old double garages converted to contemporary living quarters using the existing footprint can be visually transformative. Talk to an architect; riai.ie.