Granny flat questions, answered

Not if it meets Class 3A of S.I. No. 340/2026. Since 27 July 2026, a detached garden home of 32–45 m² in the rear garden of your main house is exempt, provided at least 25 m² of garden remains, it is at least 0.6 m from any boundary, it has its own access within the garden (no new entrance onto the road), you live in the main house as your sole or main residence, and you notify the council 14 days before work starts. Building Control still applies in full, because a garden home is a new dwelling. We confirm your site at a free visit.

Yes. The 45 m² cap counts the garden home together with anything already built in the same rear garden under Class 3 — sheds, garden rooms, home offices. With a 10 m² shed, the garden home can be up to 35 m². The home itself must still be at least 32 m², so a shed of more than 13 m² would need to come down first.

At least 0.6 m from any boundary wall or party boundary, and any window must be at least 0.6 m from the boundary it faces. Fire-safety rules on walls and windows close to a boundary can push it further in, so we treat 0.6 m as a minimum, not a target, and design around both.

Often, yes. If the house uses a septic tank or treatment system, the garden home must not encroach on the percolation area, the existing system must have capacity for the extra load to the EPA Code of Practice, and no new treatment unit may be added. We check the percolation area and the system at the free site visit.

It depends mostly on access and space. You still need at least 25 m² of garden left over and 0.6 m to every boundary. You cannot create a new gate or entrance onto a road (condition 10), and the garden home needs its own pedestrian access within your property (condition 11). An existing rear gate or laneway access can help; where the only way into the back garden is through the house, we check your layout against condition 11 at the free site visit. For the build itself, our on-site ICF pour doesn't need a crane, so tight access is often workable.

Yes. A notification goes to your planning authority at least 14 days before work starts, saying you are using Class 3A, confirming the site meets the conditions, giving the reason for the garden home, and including the location and Eircode. It is free, and there is no application to decide: the council records it. The council forms include a declaration (sole or main residence, no sale or short-term letting) that only the owner can make, so the owner signs; an agent can prepare and lodge it. It is separate from the building control Commencement Notice (below), and we prepare and lodge both for you; you sign them as the owner. Every council’s form and address is in our Class 3A notification guide, linked below.

Yes. A Class 3A garden home is a new dwelling, so full building control applies: a Commencement Notice with compliance documents is lodged on the Building Control Management System (BCMS) 14–28 days before work starts, with a design certifier, an assigned certifier and a competent builder, and a Certificate of Compliance on Completion must be registered before anyone moves in. The owner registers on BCMS and signs the Commencement Notice. The BCMS fee is €30. Lodge the Commencement Notice first (Kildare asks for its BCMS number on the notification), then send the council notification the same day. Work can start at least 14 days after both, and within 28 days of the Commencement Notice.

When the Government approved the garden home exemption in April 2026, ministers said it would be reviewed within 18 months. Nobody can say yet what a review will change. What is fixed in law today: S.I. No. 340/2026 runs until 31 December 2030, and a garden home must be both started and finished inside that window.

No. At 25 m² it is below the 32 m² Class 3A minimum, so it is sold as a garden room under Class 3 (S.I. No. 338/2026). It is for use with your home — an office, studio, gym or hobby room — and cannot be lived in or slept in without planning permission.

Usually not. Garden structures behind your house need no planning permission if, together with any existing sheds, they total no more than 30 m², leave at least 25 m² of garden, and stay under 3 m high (4 m with a tiled or slated pitched roof). It must not sit forward of the front wall of the house. We confirm it at your free site visit.

Not both under the exemptions. A 25 m² Garden Studio counts towards the 45 m² Class 3A limit, leaving 20 m² — below the 32 m² minimum for a garden home. A garden home alongside it would need planning permission, which we can handle.

No. The Garden Studio is a Class 3 garden room, not a dwelling. It is not built under Class 3A, so neither the Class 3A notification nor the new-dwelling building control process (Commencement Notice, certifiers and completion certificate) applies to it. We confirm what applies to your site at your free site visit.

There is no grant for building a garden home or granny flat. SEAI home energy grants are for upgrading existing homes — the solar PV and heat pump grants need a home built and occupied before 2021 — so a new garden home does not qualify. The Housing Adaptation Grants are the ones to ask your council about. These are means-tested grants run by your local council for adapting a home. The council decides whether a new detached garden home qualifies, and no grant is paid for works that start before approval — ask your council before you sign anything.

From savings, or by borrowing: mortgage top-up or equity release; credit union loan; personal loan. We don't publish interest rates or recommend lenders — talk to your own lender, credit union or an independent financial adviser.

Possibly — ask your council. Housing Adaptation Grant for People with a Disability up to €40,000; Housing Aid for Older People up to €10,700; Mobility Aids Grant up to €8,000. These are means-tested grants run by your local council for adapting a home. The council decides whether a new detached garden home qualifies, and no grant is paid for works that start before approval — ask your council before you sign anything.

Designed to BER A0, the top of SEAI’s new scale. A0 is a design target, not a certificate: the Department’s guidance says a BER is not legally required for a standalone building under 50 m². We can arrange a BER assessment if you want one. Every new Irish home, ICF or timber frame, must meet the same nZEB standard under Part L, including walls of 0.18 W/m²K or better and an airtightness test.

Not by law. The Department’s guidance says a BER is not legally required for a standalone building under 50 m². The building control process still applies in full, because a garden home is a new dwelling. We can arrange a BER assessment if you want one.

Every new Irish home, ICF or timber frame, must meet the same nZEB standard under Part L (TGD L 2022), including walls of 0.18 W/m²K or better and an airtightness test, so against a well-built timber-frame home the difference is modest and depends on design. ICF adds continuous insulation on both sides of a concrete core: NSAI-certified ICF wall systems reach about 0.10–0.25 W/m²K depending on insulation thickness. A peer-reviewed UK study (Mantesi et al., Energy and Buildings, 2019) found the concrete core cut wall heat loss compared with a lightweight wall with the same insulation, and a controlled US field test (NAHB Research Center for HUD, 1999) found ICF homes used about a fifth less heating energy than a timber twin, mainly because their walls were better insulated. Nua Living homes are designed to BER A0 on SEAI’s new scale, as a design target; a BER is not legally required for a standalone building under 50 m², and we can arrange a BER assessment on request.