Granny Flat Planning Permission Ireland: The S.I. 340/2026 Exemption Explained

Granny flat planning permission in Ireland is changing. Under S.I. No. 340/2026, effective 27 July 2026, you can build a detached garden dwelling up to 45 m² without planning permission. The unit must be in the rear garden, leave 25 m² of outdoor space, have a separate entrance, and the owner must live in the main house.

What are the exact rules for the S.I. No. 340/2026 planning exemption?

To qualify for the exemption under S.I. No. 340/2026, your granny flat must meet strict size, location, and occupancy conditions. The Irish government introduced this measure to create more housing options in existing residential areas. The exemption currently runs until 31 December 2030.

If you plan to build without a standard planning application, your project must tick every one of these boxes:

• Size limit: The detached garden dwelling cannot exceed 45 m² in floor area.
• Location: The unit must sit entirely within the rear garden of the main home.
• Remaining space: You must retain at least 25 m² of private open garden space after the build.
• Access: The new dwelling must have its own separate entrance.
• Occupancy: The owner of the property must live in the principal dwelling.

If your site fails to meet even one of these criteria, you will need to submit a standard planning application to your local council. You can read more about preparing your site in our planning guide.

Do building regulations still apply to exempt granny flats?

Yes, even if your granny flat is exempt from planning permission, it must fully comply with Irish Building Control, fire safety, and BER regulations. An exemption from planning is never an exemption from safe, legal building standards.

Ireland's building regulations require all new dwellings to meet the nZEB (Nearly Zero Energy Building) standard, which translates to a minimum BER of A2. You must ensure proper ventilation, structural integrity, and fire separation distances from boundaries and the main house.

At Nua Living, we design our units to reach BER A1–A0. We achieve this high thermal performance through ICF (Insulated Concrete Formwork) construction. This method creates an airtight, highly insulated structure that easily meets and exceeds the strict Irish building control requirements.

How much does an exempt granny flat cost to build?

A planning-exempt granny flat from Nua Living costs between €69,000 and €126,500 plus VAT at 13.5%, depending on the size you choose. We offer fixed prices for our standard designs, which include the design work, the physical build, and full project management.

These fixed prices exclude site works, utility connections, and professional fees, as these vary heavily depending on your specific garden. Below is a breakdown of our standard sizes and how they align with the new exemption rules.

Unit Size	Description	Base Price (Excl. VAT)	Planning Status under S.I. 340/2026
25 m²	Studio Flat	€69,000	Exempt (if conditions met)
33 m²	1 Bed Granny Flat	€93,900	Exempt (if conditions met)
45 m²	1-or-2 Bed Granny Flat	€126,500	Exempt (if conditions met)
48 m²	2 Bed Granny Flat	€134,500	Requires Planning Permission

Notice that our 48 m² unit exceeds the 45 m² limit set by S.I. No. 340/2026. If you want this larger model, you must apply for standard planning permission. You can view the layouts for these units on our granny flats page.

How long does it take to build an ICF granny flat?

The on-site structural build for an ICF granny flat takes just 5 to 10 days once the foundations are ready. However, design, planning checks, and utility connections add lead-time before that structural work can begin.

Many people misunderstand how ICF works. It is not a timber-frame or steel-frame building, and it is not delivered fully built on a lorry. ICF involves setting up two permanent layers of insulation on your site and pouring a reinforced concrete core directly between them.

This creates a solid, permanent concrete building in your garden. Because the insulation acts as the formwork for the concrete, the walls go up rapidly. You can learn more about the steps involved on our process page.

Frequently Asked Questions

Do I need planning permission for a granny flat in Ireland?

From 27 July 2026, you do not need planning permission for a detached granny flat up to 45 m² in your rear garden, provided you leave 25 m² of garden space, create a separate entrance, and the owner lives in the main house. Units over 45 m² or those built before this date still require planning permission.

Can I rent out a planning-exempt granny flat?

The S.I. No. 340/2026 exemption requires the owner to live in the principal dwelling. You must check with your local authority regarding the specific rules for renting out the secondary unit, as local housing policies dictate rental usage.

Are Nua Living granny flats delivered fully built?

No. Nua Living builds using ICF (Insulated Concrete Formwork). This means the reinforced concrete core is poured on site between permanent insulation layers. The homes are built permanently in your garden, not delivered on a lorry.

What is included in the Nua Living fixed price?

The fixed price includes the design, the ICF build, and full project management. It excludes VAT at 13.5%, site works, utility connections, and professional fees.

Ready to assess your site?

The best way to know for sure if your garden meets the 25 m² remaining space rule and the access requirements is to have a professional look at it. We offer a free, no-obligation site visit to help you figure out your options. Check if your garden qualifies and get a fixed price.