Log Cabins, Mobile Homes & Garden Cabins: Planning Permission in Ireland

Log Cabins, Mobile Homes and Modular Homes in Your Garden: The 2026 Rules

On 27 July 2026, the biggest change to Ireland's household planning exemptions in decades came into operation. Under the new Class 3A exemption (SI 340/2026), you can now build a detached, habitable garden dwelling of 32 to 45 square metres in your rear garden without planning permission — if you meet every condition.

The same package of regulations raised the ordinary garden structure limit (sheds, garden rooms, home offices) from 25 to 30 square metres, and the rear extension limit from 40 to 45 square metres.

This guide explains what is and isn't allowed, the conditions in plain English, the mandatory council notification, and your options if your project doesn't fit the exemption.

First, the Big Misconception: Mobile Homes Are NOT Exempt

The new rules are widely reported as allowing "mobile homes in gardens." They do not. Condition 5 of Class 3A states that the structure "shall not be temporary in nature, such as a caravan or mobile home."

• Placing a mobile home or static caravan in your garden and living in it still requires planning permission. It is a material change of use of the land, and councils regularly issue enforcement notices requiring removal.
• Some councils tolerate a mobile home as temporary accommodation while you build or renovate the main house, but only with a time-limited permission or written agreement — never assume.
• What IS now exempt is a permanent building — a modular home, log cabin, or garden dwelling constructed to full Building Regulations standards — within the Class 3A limits below.

The distinction is construction quality, not appearance: a factory-built modular unit craned into the garden can qualify, but it must be a permanent structure that complies with the Building Regulations (structure, fire safety, insulation, ventilation, energy).

The Class 3A Exemption at a Glance

The Conditions in Detail

Size (32-45 square metres). There is a *minimum* as well as a maximum: units under 32 square metres are not covered, because habitable dwellings must meet minimum accommodation standards. Crucially, the 45 square metre cap is measured together with any structures already built under the garden shed exemption (Class 3). If you already have a 20 square metre shed, only 25 square metres of cabin allowance remains — which is below the 32 square metre minimum, so you would need to remove the shed or apply for permission.

Rear garden and boundaries. The cabin must be in the rear garden, at least 0.6 metres from any wall or party boundary, with any windows at least 0.6 metres from the boundary they face. After building it, the main house must still have at least 25 square metres of private open space.

Services. The unit must be linked to the main house's services — there can be no separate connection to water, wastewater, or other utilities. If the house is on a septic tank, the cabin must not encroach on the percolation area, the existing treatment system must have capacity for the additional loading under the EPA Code of Practice, and no additional treatment unit may be installed.

Access. No new vehicular or pedestrian access onto a road may be created, and independent pedestrian and/or wheelchair access to the cabin must be provided within the property. In practice this is straightforward for detached and semi-detached houses with side access; for a mid-terrace house with no side passage, providing independent access without new road frontage can be difficult — get advice before committing.

Ownership and use. The main house must be the owner's sole or main residence when works begin, must not have been subdivided, and the cabin can only ever be occupied in conjunction with it. Long-term renting is allowed — and rent of up to €14,000 per year can qualify for rent-a-room tax relief — but short-term letting is expressly prohibited, as is selling the cabin separately.

Protected structures. As with all exemptions, Class 3A does not apply to protected structures or where a condition of an existing planning permission would be contravened, and works in an Architectural Conservation Area need care.

The 14-Day Council Notification

Unusually for an exemption, Class 3A requires you to notify your local planning authority in writing at least 14 days before starting work. The notification must:

• State your intention to use the Class 3A exemption
• Confirm that the site meets the requirements of the Regulations
• State the reason for the intended use
• Include the location and Eircode of the property

Councils keep a register of these notifications and report the numbers to the Minister annually. Skipping the notification means the development is not exempt — it becomes unauthorised development, with all the enforcement and resale problems that brings.

Building Regulations Still Apply in Full

Class 3A removes the *planning application* — nothing else. The cabin is a dwelling in law, so it must comply with the Building Regulations, including:

• Part A (structure) and Part B (fire safety)
• Part L (energy conservation) — a habitable dwelling needs proper insulation, airtightness, and heating
• Building Control requirements, including a commencement notice

This is where cheap "garden cabin" offerings fall down: many products marketed for garden use are not built to dwelling standard. Before ordering anything, have an architect, engineer, or assigned certifier confirm the unit can be certified as compliant — non-compliance surfaces at the worst possible moments, such as selling the house or making an insurance claim.

What If Your Project Doesn't Qualify?

You still have good options — these routes need a planning application, and councils grant many of them:

• Bigger than 45 square metres, or a small garden: apply for full planning permission for a garden dwelling. See How to Apply.
• A cabin already built without permission: apply for retention permission — but note retention cannot regularise a unit that breaches Building Regulations, so get professional advice first.
• An existing mobile home someone lives in: this is unauthorised development. Options are removal, replacement with a compliant Class 3A unit, or a planning application — talk to a professional before the council's enforcement letter arrives.
• Splitting the main house instead: the new Class 1A exemption (SI 339/2026) allows subdividing a house into two self-contained units of at least 32 square metres each, with the same 14-day notification — but you cannot combine it with Class 3A on the same property.

Check Your Project in 2 Minutes

Our free exemption checker now includes the full Class 3A question path — floor area, garden size, services, access, and use — and tells you whether your cabin is likely exempt or needs an application.

Related Guides

• Exempted Development — all exemption thresholds and conditions
• Do I Need Planning Permission? — general guide and Section 5 Declarations
• Retention Planning Permission — if something is already built
• How to Apply — the full application process

Disclaimer

This guide provides general information about the Class 3A exemption (SI 340/2026) and related rules and is not legal or professional advice. Every condition of an exemption must be met for it to apply, and Building Regulations compliance is a separate legal requirement. Always verify with your local authority or a qualified professional before ordering a unit or starting work.