Short answer
A granny flat in Ireland can be an attached extension or a detached unit in the back garden. Planning rules for these were updated recently, and some smaller detached units in the rear garden can now be exempt if strict conditions are met, so check the current rules with your council before design. Every granny flat must meet the Building Regulations. Phoenix Maco Ltd designs-and-builds granny flats in Dublin and prices each one after a free site visit.
Key points
- Attached or detached in the rear garden.
- Exemption rules changed recently; check with your council.
- Building Regulations always apply: fire, structure, energy.
- Water, drainage and electricity connections are a major cost.
- Get a written quote after a site visit.
Attached vs detached granny flat
An attached granny flat is built like an extension and shares services with the house. A detached unit sits in the back garden and needs its own foundations, drainage and connections.
Planning permission
Older rules let you build a family flat as part of an extension. Newer exempted-development rules allow some detached rear-garden units within a size limit and with garden, height and boundary conditions. Protected structures and some areas still need permission. Confirm the current regulations with your council before you design.
What drives the cost
- Size and layout (bedroom, shower room, kitchenette).
- Foundations and site access to the back garden.
- Drainage, water and electricity connections.
- Insulation, heating and finishes.
- Design and certification fees.
Frequently asked questions
- Do I need planning permission for a granny flat in Ireland?
- It depends on the type, size and location. Some rear-garden units may now be exempt under updated rules; check with your council.
- How much does a granny flat cost?
- It depends on size, foundations, connections and finishes. Get a written quote after a site visit.
- How long does a granny flat take to build?
- Usually a few months on site, after design and any planning.
- Do Building Regulations apply?
- Yes, always: structure, fire safety, ventilation and energy performance.
- Do you build granny flats in Dublin?
- Yes. Phoenix Maco Ltd builds granny flats across Dublin. Call or WhatsApp 083 874 5535.
Official Irish sources
Rules, grant values and rates change. This article is general information, not professional advice — confirm the current position with the relevant body or your own architect, engineer or surveyor.