What are the granny flat rules in Mount Gambier for 2026? In South Australia, ancillary accommodation (a granny flat) can now be up to 70 m2, up from 60 m2, and it no longer has to share a kitchen, bathroom or laundry with the main house, according to the Premier of SA. PlanSA confirms all existing ancillary accommodation can be leased or rented out. You still need development approval, which means planning consent and building consent.
This guide is for homeowners in Mount Gambier, Millicent, Penola, Naracoorte and the rural districts of the Limestone Coast. Some want a home for an ageing parent. Others want rental income or a place for a farm or forestry worker. The hard part is usually getting a builder for a small job, not the rules.
What the SA changes mean for you
- Up to 70 m2 of floor area for ancillary accommodation.
- It can have its own kitchen, bathroom and laundry.
- Existing granny flats can be leased or rented out, according to PlanSA.
- Planning consent and building consent are still needed.
In the city, applications go through the City of Mount Gambier. Outside it, the District Council of Grant, Wattle Range Council and Naracoorte Lucindale Council handle local matters. Each zone in the Planning and Design Code can apply its own setbacks and site coverage rules.
Why modular suits the Limestone Coast
A modular granny flat is built as complete steel-framed modules, then trucked in and craned onto prepared footings. Most of the work happens off your property. What is left on site is footings, services, the lift and the final connections.
That suits a region where trades are often booked out on larger work. A local builder can install and connect a modular granny flat in a short window rather than run a long site job. Cold, wet winters in the South East slow site framing, but they do not stop work in the factory.
What EcoPrestige supplies
As the manufacturer, EcoPrestige is responsible for every module: built and inspected in an offsite factory to Australian engineering and QA, then delivered to site. The modules come with the kitchen, bathroom, laundry, linings, windows and electrical rough-in already fitted.
- Engineered structural steel modules designed for the site conditions.
- A bill of quantities so your builder can price footings and services.
- A lifting and install sequence for the crane crew.
- Supply price quoted for your site.
How the design and permit package works is explained on our Domestic Program page.
What does not fit
- Tight access: a backyard with no truck or crane reach, or with power lines and large trees in the way, may not suit modules.
- Karst and limestone ground: the region’s limestone and sinkhole-prone ground can need a soil test and deeper or different footings.
- Bushfire overlays: rural and forest-edge lots may face bushfire requirements that change materials and setbacks.
- Heritage areas: heritage places and character areas in the city add planning steps.
- Slopes and low ground: sloping or wet sites add footing and drainage cost.
Our feasibility guide explains how to test a site before you commit.
The approval path in SA
We design and draft your home, then coordinate engineering, the energy rating and certification. Development approval in South Australia is two parts: planning consent and building consent. Both are assessed by the council or an accredited professional under the Planning, Development and Infrastructure Act. SA has no designer or engineer registration category, and the energy assessment is independent of the design. A granny flat is typically Class 1a, confirmed by your building surveyor. Read how building permits work for modular buildings for inspections and final sign-off. Always confirm with your building surveyor or certifier.
The programme
The Domestic Program has two steps. Step 1 is feasibility on your site: zone, ground, access and services. Step 2 is design, permits and build by the practitioners SA requires. Once development approval is granted, the factory makes the modules while your builder prepares footings and services in Mount Gambier or on the farm. Factory and site work run in parallel, so time on site is shorter. The builder on site is your own builder or a local Limestone Coast builder using our bill of quantities.
What to send us
- 1. The property address and certificate of title.
- 2. Who will live there, or whether it will be rented.
- 3. Photos of the yard, side access and street.
- 4. Any soil test or footing report you already have.
- 5. Sewer, septic or other wastewater on the lot.
- 6. Your builder’s name, if you have one.
For more on the state, see modular construction in South Australia and transportable buildings in South Australia.
Frequently asked questions
Can I rent out a granny flat in Mount Gambier?
Yes. PlanSA confirms all existing ancillary accommodation can be leased or rented out. A new granny flat still needs planning consent and building consent.
How big can a granny flat be in South Australia?
Up to 70 m2, up from 60 m2, according to the Premier of SA. It no longer has to share a kitchen, bathroom or laundry with the main house.
Does limestone ground affect a granny flat on the Limestone Coast?
It can. Limestone and sinkhole-prone ground may need a soil test and deeper or different footings. Your engineer sets the footing design for the site.
Rules last checked: 29 October 2026. Confirm with your council and building surveyor or certifier.
Send us your Mount Gambier or Limestone Coast block
Send the site, the use and any drawings to prebuilt@ecoprestige.com.au or download our technical brochures.