Building a Granny Flat in Ireland: What You Need to Know

Adding a granny flat to your property can be a great way of maximising available space, and potentially earning income by renting it out. 


  • Self-contained apartments attached as an extension to the main house
  • Traditionally used to accommodate elderly relatives
  • In more recent times, the use of granny flats has expanded to accommodate adult children still living at home, as well as guests and lodgers
  • Usually contains a bedroom (or bedrooms) and bathroom
  • May also contain a kitchenette and living rooms


It is important to know what you want from your granny flat before you begin the process of constructing it. Take into consideration the main purpose of it: is it to accommodate a family member or to rent out? Will it be multipurpose?

If you are building a granny flat for someone in particular it is a good idea to think about what they will need. For instance, an elderly relative might require special fixtures, such as handrails, or a limited amount of stairs. Similarly, if the function of the granny flat is for rental purposes, you may want to take the tenant’s desire for privacy into account. The addition of a kitchenette, for example, could make your room-to-rent particularly attractive for potential tenants.

interior of granny flat

Once you have recognised what you need from your granny flat you should have plans drawn up accordingly. It is important to ensure that you are satisfied with the plans before construction begins, as any changes can lead to delays in the process and a potential rise in cost for the project.


The rental potential of a granny flat in Ireland has greatly increased recently as a result of the shortage of rental properties in the country. People (particularly students) are now more inclined to look for a room to rent, rather than an entire property, than before. This is in large part due to a rise in rental prices resulting from the lack of available properties for tenants.

Some granny flats will be constructed by parents for their adult children who are unable to find a suitable rental property, or who are saving for a mortgage. This short-term use of the granny flat can be converted to long-term rental income for the household, when the child moves out and tenants can be moved in.

Homeowners can make up to €14,000 free of income-tax, if they are eligible for the Rent-a-Room relief scheme. For a room to be eligible for this relief scheme it must meet a number of requirements, including being attached and accessible to the main house. This scheme is a great incentive for people who are considering building a granny flat as it can potentially mean that the cost of the project is covered within a year or two of renting it out.


Regulations on granny flats differ from one local authority to the next, so it is essential to consult with a planning expert before you make any decisions or begin construction.

planning permission for granny flats

General guidelines relating to planning permission are available on

In general, planning permission is not required if the extension does not increase the original floor area of the house by more than 40 square metres and is not higher than the house.

However, planning permission will be needed if the granny flat is intended to be a stand-alone dwelling. In being a self-contained unit, such a structure would ensure that the homeowner must register as a landlord with the RTB, and meet a number of regulations if the dwelling is intended to be rented out (something which a homeowner with an attached granny flat is exempt from).

Building a granny flat can be a lucrative addition to your property, and can maximise on potential space. Before beginning construction, it is important to know what you want from your granny flat, so that the process can be as successful as possible. It is always important to consult experts regarding any property project, as well as your local authority.

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