Updated for S.I. 340 of 2026 · in force 27 July 2026
Planning permission for a modular home in Ireland
Yes, a modular home used as a dwelling needs planning permission — with one new exception. Since 27 July 2026 a detached home of 32–45 m² in the rear garden of the house you own and live in can be built on a 14-day notification instead of a planning application. Here is exactly what qualifies, what doesn't, and what still applies either way.
Three routes · which is yours
Notify
32–45 m² home in your own rear garden — 14 days' notice to the council, no application.
Exempt
Garden room up to 30 m² that nobody lives in — no permission, no notification.
Apply
Everything else — any home over 45 m², any site without a house you live in, every 3- and 4-bed.
Which route applies
Three ways a modular home gets built legally
The exempted development regulations had not been substantially updated in almost 25 years. The 2026 regulations added a route that did not exist before, widened two that did, and left the full planning process untouched for everything else.
Class 3A · new in 2026
A home in your rear garden
A permanent detached home of 32–45 m² behind the house you own and live in. No planning application — a notification to the council at least 14 days before work starts. Open until 31 December 2030, and every one of the twenty conditions below has to be met.
The conditions →Class 3 · widened in 2026
A garden room nobody lives in
An office, studio, gym or store of up to 30 m² (the limit was 25 m² until July 2026), behind the building line, no taller than 3 m — or 4 m with a tiled or slated pitched roof — and leaving 25 m² of garden. No permission and no notification. The condition that matters: it cannot be used as a dwelling.
Garden rooms →Full application
Everything else
Any home over 45 m². Any site without an existing house you live in — a field, an infill plot, a holiday site. Any garden unit you want to sell or let separately. Every three- and four-bedroom home we build, and most two-beds. The process is the same as for any house; it is set out below.
The process →The 45 m² exemption
Class 3A, condition by condition
The regulation is one paragraph of description and twenty numbered conditions. Most coverage quotes the headline — "45 m², no planning permission" — and stops. The conditions are where people get caught, so here they are, grouped, with the figures as written.
The Department's own name for it is a detached auxiliary dwelling. The word that does the work is auxiliary: it is a second home attached, in law, to the first one.
- straightenSize — not less than 32 m² and not more than 45 m² — and any garden structure already built under Class 3 in the same garden counts toward the 45. An existing 12 m² shed leaves room for a 33 m² home, not a 45 m² one.
- roofingHeight — 4 metres with a tiled or slated pitched roof; 3 metres for any other roof. A standing-seam or flat metal roof is in the 3-metre category. Ask for the overall height of any module before you plan around this exemption.
- home_workThe main house — must be your sole or main residence on the day work starts, and you must own it. The unit goes in the rear garden. It cannot be used at all if the house has been subdivided under the separate Class 1A exemption.
- foundationThe garden — at least 25 m² of private open space must remain exclusively for the main house. The structure sits at least 0.6 m from any wall or boundary, and any window faces its boundary from at least 0.6 m.
- routeAccess — independent pedestrian and wheelchair access to the unit within the site, and no new vehicular or pedestrian access onto a public road.
- water_dropServices — no separate connection to utilities, including water and wastewater — it shares the main house's. On a septic tank, the system must have capacity for the extra loading, comply with the EPA Code of Practice, and the unit must not encroach on the percolation area; no additional treatment unit may be added.
- family_homeUse — occupied in conjunction with the main house. Cannot be sold or subdivided separately. Cannot be used for short-term letting.
- precision_manufacturingPermanence — must not be temporary in nature — the regulation names caravans and mobile homes as what is excluded. A factory-built home on foundations is a permanent structure.
- descriptionPaperwork — a notification to the planning authority at least 14 days before work starts, giving the location and Eircode, confirming the site meets the conditions, and stating the reason. The council keeps a register and reports to the Minister annually.
- engineeringBuilding regulations — apply in full, the regulation says so explicitly — fire safety included. See below.
- check_circleTime limit — the work must be both commenced and completed between 27 July 2026 and 31 December 2030.
Which Don Modular sizes fit which route
| Floor area | Home | Rear garden of your own house |
|---|---|---|
| 25.2 – 28.8 m² | 1-bed or garden room | Exempt as a garden room nobody lives in (Class 3, ≤30 m²). As a home: under the 32 m² minimum, so a planning application. |
| 32.2 – 39.6 m² | 1-bed | Notification under Class 3A, if every condition is met. |
| 40.0 – 43.7 m² | 2-bed | Notification under Class 3A, if every condition is met. |
| 46.0 – 55.2 m² | 2-bed | Over 45 m² — planning application. |
| 70 m² and up | 3-bed · 4-bed | Planning application, on any site. |
On any site other than the rear garden of the house you own and live in — a plot, a field, a holiday site — every size is a planning application. The height condition is the one most likely to decide a factory-built module: confirm the overall height of your configuration against the 3-metre limit before you notify the council.
Not sure? Ask for a Section 5 declaration
If you cannot tell whether your plan is exempt, you can ask your planning authority for a formal declaration under Section 5 of the Planning and Development Act. They have four weeks to decide, and the answer is binding. It is far cheaper than finding out through an enforcement letter.
Not the same thing
Building regulations don't go away
Planning permission and building control are two separate systems, and the new exemption only touches the first. Condition 4 of Class 3A says it in terms: the Building Regulations, including fire safety, and the Building Control Regulations apply. A garden home is a new dwelling in building-control law whether or not it needed planning.
In practice that means a Commencement Notice lodged on the Building Control Management System between 14 and 28 days before work starts, and a home that meets the Building Regulations in full — Part A structure, Part B fire safety, Part M access (which is also why the exemption requires independent wheelchair access), Part L energy, and the rest. The Department published an information note in July 2026 on how these apply to auxiliary dwellings; an industry estimate quoted by the Irish Times put the professional fees for getting the compliance paperwork right on a small residential project at around €4,000–€5,000.
Where a factory-built home helps is that the specification is fixed and documented before it leaves the factory: on a Don Modular Home that is a G550 galvanised steel frame, 200 mm insulation, fire sprinklers to BS 9251, A1 non-combustible cladding, and electrics to the Irish ET101 rules on every module. The site-specific items — foundations, services, the junction with the ground — are what your engineer certifies.
The full route
If you need planning permission
A modular home on its own site goes through exactly the same process as any new house. Planners assess the site and the design, not the construction method — your drawings show a house, and it is judged as one.
- architecturePre-planning — most councils offer a pre-planning meeting; for a rural one-off site it is worth having, because the county development plan's rural housing policy — a local connection to the area, usually — is what decides most applications.
- descriptionNotices — a site notice at the property and a notice in a local newspaper, before you apply. The site notice stays up for at least five weeks; the application must reach the council within two weeks of the newspaper notice.
- publicApplication — online through the national planning portal or by post — site location map, drawings, the notice details, and the fee: €65 for a house, €34 for an extension.
- format_quoteSubmissions — anyone can object to or support the application for five weeks, for a €20 fee.
- check_circleDecision — the council must decide within eight weeks of receiving the application — longer if they request further information.
- routeAppeal — four weeks from the decision for an appeal to An Coimisiún Pleanála, by you or by anyone who made a submission.
- constructionPermission — normally lasts five years. We build to your grant of permission and the drawings attached to it.
What varies by county
The regulations are national; the policies applied to a one-off site are not. Rural housing policy, Gaeltacht language conditions, landscape designations and heritage buffers differ from one development plan to the next, which is why each of our county pages covers the planning position for that county.
Extensions: now 45 m²
The same regulations raised the rear-extension exemption from 40 m² to 45 m². The 45 includes every previous extension to the house; the extension cannot be higher than the house; at least 25 m² of rear garden must remain; and anything above ground floor is capped at 12 m² for a terraced or semi-detached house, 20 m² for a detached one, at least 2 m from the boundary. Modular extensions →
Questions
Modular home planning permission — FAQ
Do you need planning permission for a modular home in Ireland?
Usually, yes. A modular home used as a dwelling is treated like any other new house, and on its own site — a field, a plot, a holiday site — it needs full planning permission. The one exception since 27 July 2026 is a detached home of 32–45 m² in the rear garden of the house you own and live in, which can be built on a 14-day notification to the council under Class 3A of the exempted development regulations, provided every condition is met.
What are the new rules for modular homes in Ireland in 2026?
S.I. 340 of 2026 came into force on 27 July 2026 and created Class 3A, a "detached auxiliary dwelling": a permanent detached home of 32–45 m² in the rear garden of your principal residence, built between 27 July 2026 and 31 December 2030, sharing the main house's services, with 25 m² of garden left for the house, 0.6 m from boundaries, no more than 3 m tall (4 m with a tiled or slated pitched roof), not sold or let separately, and notified to the council at least 14 days before work starts. The same regulations raised the rear-extension exemption from 40 m² to 45 m² and the garden-structure exemption from 25 m² to 30 m².
Are modular homes exempt from planning permission for gardens?
Two routes can apply in a rear garden. A garden room of up to 30 m² that is not lived in — an office, studio or gym — is exempt under Class 3, with no notification, as long as it stays under the height limit and leaves 25 m² of garden. A garden home that is lived in is exempt under Class 3A only if it is 32–45 m², the main house is your sole or main residence, and all twenty conditions are met, including the 14-day notification. Anything between 30 and 32 m², anything over 45 m², and anything on a site without a house you live in needs permission.
Is it hard to get planning permission for a modular home?
No harder than for any other house — the construction method is not what planners assess. What decides a one-off rural application is the county development plan's rural housing policy (a local connection to the area is usually required), the site's access and wastewater, and the design's fit with the landscape. A factory-built home is judged on the same drawings and the same policies as a block-built one. Where applications stall, it is almost always the site, not the building.
What is the 7-year rule for planning permission in Ireland?
Under the Planning and Development Act, a planning authority generally cannot start enforcement proceedings more than seven years after an unauthorised development was carried out. It does not make the development authorised: it remains unauthorised, which surfaces when you sell, remortgage, or apply for permission for anything else on the site. It is not a route anyone should plan around.
Does a log cabin or mobile home qualify for the 45 m² exemption?
A log cabin can, if it is permanent, 32–45 m², and meets every other condition — including the 3-metre height limit that applies to any roof that is not tiled or slated. A caravan or mobile home does not: the regulations state that the structure must not be temporary in nature, and name caravans and mobile homes as examples of what is excluded.
Can I rent out a home built under the garden exemption?
The regulations prohibit short-term letting and separate sale or subdivision, and require the unit to be occupied in conjunction with the main house. They do not spell out every other arrangement, and the Department said the tax treatment, including how it interacts with Rent-a-Room relief, would be settled through the Budget — so check the current position with your accountant before relying on rental income.
Do building regulations still apply if I don't need planning permission?
Yes, in full. The regulations say so explicitly. A garden home is a new dwelling under the Building Control Regulations: a Commencement Notice is lodged on the Building Control Management System 14–28 days before work starts, and the home must meet the Building Regulations — fire safety, access, structure, energy — regardless of planning status. The Department published an information note on how these apply to auxiliary dwellings; budget for professional fees to get the paperwork right.
Sources
Where this page comes from
- S.I. No. 340 of 2026 — Planning and Development (Exempted Development (Act of 2000)) (No. 3) Regulations 2026, signed 16 July 2026, in operation 27 July 2026. The Class 3A text and all twenty conditions.
- Circular PLR-02/2026 and the Department's press release of 27 July 2026, which cover all seven 2026 regulations.
- Citizens Information — planning permission for altering your house (edited 27 July 2026) and planning permission (edited 28 July 2026): the extension, garden-structure and application-process figures.
- The Irish Times, "Modular homes: no planning permission required but construction regulations still apply", 4 August 2026: the building-control commentary and fee estimate.
This page is general information, checked against the sources above on 8 October 2026. It is not legal advice. The conditions are applied to your specific site by your planning authority; confirm with them, or request a Section 5 declaration, before you commit.
Next step
Tell us the site, and we'll tell you the route
Send the site's location and a few photos — for a garden, the house and the garden; for a plot, the access. We'll say plainly whether it looks like a notification or an application, and supply the drawings either way.