The Short Version

A secondary dwelling is a self-contained home — with its own kitchen, bathroom, bedroom and living area — on the same lot as your primary house. It’s smaller than the main dwelling, shares the same address, and can’t be separately titled or sold off on its own.

That’s the one-sentence answer. The rest of this article is about everything that sentence doesn’t cover — because most of the confusion around secondary dwellings comes from the gap between what people think they can build and what the planning framework actually allows.

The Legal Definition

Under the Queensland Planning Regulation 2017 (as amended in September 2022), a secondary dwelling is defined as:

A dwelling on a lot that is used in conjunction with, but subordinate to, another dwelling on the lot.

Three words in that definition do most of the heavy lifting.

“Dwelling” — it has to be a self-contained home. A room above a garage with no kitchen isn’t a secondary dwelling. A studio with a bar fridge and no bathroom isn’t one either. It needs to function as an independent household.

“In conjunction with” — it exists alongside a primary dwelling. You can’t build a secondary dwelling on a vacant lot. There has to be a main house already.

“Subordinate to” — it has to be smaller in scale than the primary dwelling. This doesn’t just mean floor area — it means bulk, height and visual dominance. A secondary dwelling shouldn’t look like the main house on the lot. It’s a companion building, not a competitor.

What Changed in 2022

Before September 2022, a secondary dwelling in Queensland had to be occupied by someone related to or associated with the household of the primary dwelling. In practice, that meant family only. You couldn’t rent it to a stranger on the open market.

The amendment removed that restriction entirely. A secondary dwelling can now be rented to anyone — no relationship to the primary household required.

That single change transformed secondary dwellings from a family convenience into a genuine housing and income asset. It’s the reason there’s suddenly so much interest in building them. And it’s why the State Government is now working on standardised design and siting provisions through the Distinctly Queensland Design Series — because when you allow secondary dwellings to be rented out statewide, you need consistent rules about what they look like and where they can sit on a lot.

Those reforms are still underway. Consultation on a proposed State Code for secondary dwellings closed in November 2024, and the final provisions haven’t been enacted yet. In the meantime, individual council planning schemes still govern what’s allowed where.

What a Secondary Dwelling Is

To qualify as a secondary dwelling in Queensland, a building needs to meet all of the following:

Self-contained — kitchen, bathroom, bedroom and living area, all within the one building
On the same lot as an existing primary dwelling
Subordinate — smaller in scale, bulk and visual presence than the primary house
Same address — shares the address of the main dwelling, can’t have its own separate title
Connected to services — water, sewer (or on-site wastewater), and electricity
Permanent — a fixed structure on a permanent foundation, not a moveable or temporary building

A secondary dwelling can be detached (a separate building in the backyard) or attached to the main house (built underneath or to the side). It can be single-storey or, in some cases, two-storey — depending on council rules and the bulk and scale provisions in your local planning scheme.

What a Secondary Dwelling Is Not

This is where most of the confusion lives. People use a lot of words interchangeably — secondary dwelling, granny flat, dual occupancy, tiny home, modular home — as though they all mean the same thing. They don’t. The distinctions are legal, structural and financial, and getting them wrong can cost you months and tens of thousands of dollars in the wrong approval pathway.

Not a dual occupancy

A dual occupancy is two independent dwellings of similar size and scale on the same lot. Neither is subordinate to the other. Dual occupancies have a completely different approval pathway, often requiring a development application rather than just building approval. The infrastructure charges alone can be significantly higher — some councils charge $28,000 or more for dual occupancy versus nothing (or a reduced charge) for a secondary dwelling that stays under certain size thresholds.

If your secondary dwelling is too large relative to the primary house, or looks too dominant on the lot, a council may reclassify it as a dual occupancy. That triggers different assessment, different charges and potentially different setback requirements. Size limits exist for a reason.

Not a caravan, transportable or moveable dwelling

A secondary dwelling must be a permanent structure. Caravans, converted buses, shipping containers on skids, and relocatable cabins that aren’t fixed to permanent foundations don’t qualify — regardless of how well they’re fitted out. This also applies to many of the “tiny homes on wheels” you see on social media. If it has wheels, or if it can be towed away, it’s not a secondary dwelling under Queensland planning law.

Some councils allow temporary accommodation on rural land under specific conditions, but that’s a separate category with different rules. Don’t confuse the two.

Not a converted shed, garage or shipping container

A garden shed is a Class 10a building under the National Construction Code — non-habitable. A secondary dwelling is a Class 1a building — a home. The structural, insulation, fire safety, ventilation and energy efficiency requirements are completely different. You can’t convert a shed into a dwelling just by adding a bathroom and a kitchenette. It needs to meet residential building standards from the ground up.

The same applies to shipping containers. Even if you line them, insulate them and fit them with plumbing, the underlying structure wasn’t designed to meet Class 1a requirements. Some companies market container conversions as secondary dwellings, but getting them certified as Class 1a can be difficult and expensive — if it’s even possible in your council area.

Not a boarding house or multiple dwelling

A secondary dwelling is one dwelling, for one household, subordinate to one primary house. If you’re thinking about building multiple separate units on your land, that’s a different use category — likely multiple dwelling or rooming accommodation — with entirely different planning requirements.

Not a separately titled property

You cannot subdivide a secondary dwelling onto its own title. It stays part of the same lot as the primary dwelling, shares the same address, and is sold together with the main house if the property changes hands. This matters for finance — some lenders treat secondary dwellings differently when assessing property value, and you can’t take out a separate mortgage on one.

Where Does “Granny Flat” Fit?

The term “granny flat” isn’t a legal definition. It’s a colloquial label that the market — and even the Queensland Government in some of its own communications — uses to describe a secondary dwelling.

The problem with the term isn’t that it’s wrong. It’s that it carries assumptions. When most people hear “granny flat,” they picture a basic fibro annexe tacked onto the back of a house — low-spec, low-cost, temporary-feeling. That mental image sets expectations about quality, durability and value that have nothing to do with what a well-designed, properly built secondary dwelling actually is.

A secondary dwelling built to Class 1a residential standards, with steel and timber framing, full insulation, architectural fixtures and resolved interior design, is the same building classification as your primary house. The word “granny flat” doesn’t reflect that. It actively devalues it.

We use the term “secondary dwelling” throughout our content because that’s what the planning framework calls it. When we talk about what we build, we call it backyard architecture — because that’s what it is.

What Does Class 1a Actually Mean?

Every building in Australia is assigned a classification under the National Construction Code (NCC). The classification determines what structural, fire safety, energy efficiency, accessibility and amenity standards the building has to meet.

Class 1a is the classification for a single detached dwelling — a house. It’s also the classification that applies to a properly built secondary dwelling.

When we say Outhaus builds to Class 1a, we mean our dwellings are held to the same construction standards as a house. That includes:

Structural adequacy — steel and timber framing engineered for wind loads, live loads and the specific conditions of the site
Fire safety — smoke alarms, compliant materials, separation distances. If the dwelling is rented to a non-related household, additional fire and sound transmission requirements apply under the building code
Energy efficiency — minimum NatHERS rating (typically 6 stars), which governs insulation, glazing, orientation and thermal performance
Weatherproofing — designed for the local climate zone, including wind, rain and in some areas, bushfire attack levels (BAL)
Amenity — minimum room sizes, ceiling heights, natural light and ventilation requirements

This is different from a Class 10a building (sheds, garages, carports), which is non-habitable and has far less stringent requirements. It’s also different from a Class 1b building (boarding houses, guest houses, short-term accommodation), which has additional requirements around accessibility and smoke detection.

The classification matters because it determines the durability, safety and long-term value of the building. A Class 1a dwelling is a permanent residential asset. A Class 10a shed with a bed in it is a compliance risk.

Size Limits — The Quick Version

There is no single statewide size limit for secondary dwellings in Queensland. Each council sets its own maximum gross floor area, and it varies by zone, lot size and sometimes by precinct within a zone.

As a general guide across SEQ councils:

Zone Type	Typical GFA Limit	Notes
General Residential (suburban lots)	45–80m²	Varies by council and lot size. Some councils like Moreton Bay allow up to 80m² on lots under 1,000m².
Rural Residential	70–100m²	Larger allowances on larger lots. Moreton Bay allows up to 100m² in some rural residential precincts.
Rural Zone	80–100m²+	Most generous allowances. Some councils allow larger dwellings on lots over a certain threshold.

Important: These are indicative ranges, not guarantees for your property. Overlays — bushfire, flooding, vegetation, heritage — can affect what’s buildable. Always start with your specific lot, not a general table. Check your council’s interactive planning map and talk to a building certifier early.

We’re working on a separate article — Secondary Dwelling Size Limits by Council: SEQ 2026 Guide — that breaks this down council by council with current figures. For now, treat the table above as a starting point, not a specification.

How to Figure Out What You Can Build

Before you talk to any builder, modular company or architect, do these four things:

1. Check your zoning. Go to your council’s interactive planning map, search your address, and confirm the zone your property sits in. This determines the size limits, setback requirements and approval pathway.

2. Check your overlays. While you’re on the planning map, look at what overlays apply to your lot. Common ones in SEQ include bushfire, flooding, waterway corridors, vegetation management, landslide hazard and heritage. Each overlay can add requirements or restrict where you can build on the site.

3. Talk to your council’s planning enquiries team. Most SEQ councils have a duty planner service — a free initial conversation where you can describe what you want to do and get pointed in the right direction. It’s not formal advice, but it helps you understand the approval pathway before you spend money.

4. Engage a private building certifier early. A certifier can assess your site, confirm the applicable codes and standards, and tell you what approvals are needed before construction starts. This is the person who will ultimately sign off on the building, so involving them early avoids expensive surprises later.

Be cautious of any company — modular, traditional builder or otherwise — that tells you they’ll “handle everything” without first understanding your specific site. The dwelling is predictable. The site is not.

Where Outhaus Fits

We build compact, permanent dwellings to Class 1a residential standards. Steel and timber framing, full insulation, architectural fixtures and fittings, delivered complete and craned into position on your land.

Every Outhaus dwelling is designed as a secondary dwelling — subordinate to a primary house, within the size limits set by local planning schemes, and compliant with the National Construction Code. We work within the system, not around it.

Our current range covers two widths (3.2m transport-ready for suburban access and 4.0m for acreage and wider sites), six models from studio to three-bedroom, and three interior palettes. Every dwelling is built under roof in a controlled factory environment, not assembled on-site from parts.

If you want to understand what’s involved in getting one onto your land — site preparation, services, council requirements, costs — our acreage guide covers the full process for rural and rural residential properties in SEQ. Our founding story explains how we got here and why we build the way we do.

And if you want to walk through one before making any decisions, you can visit the three dwellings we built on our own property — Outhaus Ranch, 472 Laceys Creek Road, Laceys Creek QLD, in the Dayboro region. No sales pitch. Just buildings you can stand in.