Canberra’s housing pressure has pushed the ACT government to look hard at what sits behind the front fence. The Planning (Missing Middle Housing) Amendment Bill 2026, currently before the Legislative Assembly, proposes an automatic entitlement for single-dwelling Crown leases to add a secondary residence, better known around town as a granny flat. For homeowners in older inner suburbs like Ainslie, Reid, O’Connor and Deakin, where blocks tend to be larger, this is the clearest signal yet that a second dwelling is becoming a realistic option rather than a planning headache.

The reform sits inside a broader package known as the missing middle reforms, aimed at delivering more townhouses, terraces and low-rise apartments in established suburbs without waiting on large-scale rezoning. Secondary residences are the smallest and least disruptive piece of that puzzle, which is part of why they’re attracting so much attention from homeowners who already have the land but not necessarily the appetite for a major build.

What actually counts as a secondary residence

Under the Territory Plan’s Single Dwelling Housing Development Code, a secondary residence has to be self-contained and clearly subordinate to the main house on the block. Size sits between 40 and 90 square metres, and the dwelling needs its own entry, private open space, car parking and access. One change that surprises a lot of homeowners is that occupants no longer need to be related to whoever lives in the main house, which opens the door to renting the second dwelling out on the open market rather than reserving it for family.

Why container builds suit the size limit

That 40 to 90 square metre band happens to sit right in the sweet spot for shipping container and expandable container homes, which are designed around exactly this kind of footprint. Rather than committing to months of framing, cladding and trades scheduling, a container-based dwelling typically arrives largely fitted out and ready for final connection, cutting a substantial chunk of time out of the build. Suppliers such as SCS Australia design expandable and container-based homes specifically for this compact, self-contained format, which suits homeowners who want a compliant secondary residence without taking on a drawn-out renovation project.

The appeal isn’t only speed. A prefabricated build gives you cost certainty from the outset, since most of the fit-out happens off-site under controlled conditions rather than being exposed to weather delays or the usual run of on-site variations. For a homeowner weighing up whether a second dwelling is worth the disruption, that predictability often matters as much as the timeline.

Delivery is also more straightforward than most people expect. Canberra sits close enough to the major eastern seaboard depots that a container-based dwelling can be transported and craned into position on a residential block within a day, with connections to power, water and sewer handled afterwards by local trades. For a block in one of Canberra’s older suburbs, where side access can be tight, that single-lift delivery is often easier to manage than months of tradespeople moving materials in and out through a narrow driveway.

The approval process still applies

None of this skips the paperwork. A secondary residence still requires development approval, it isn’t an exempt project, and it has to meet the same standards regardless of whether it’s timber-framed or container-based. That means compliance with the Adaptable Housing standard AS4299, water sensitive design provisions that call for a meaningful reduction in mains water use, usually met with a water tank, and site coverage limits that generally cap the combined footprint of house and secondary dwelling at half the block. Zoning matters too. The block needs to sit in a residential zone, and industrial pockets like Fyshwick are unlikely to get approval regardless of what’s being built.

Homeowners also need to check plot ratio and setback requirements before committing to a design, since a smaller or oddly shaped block can rule out the full 90 square metre allowance even where the zoning itself is fine.

A practical option while reforms take shape

The Missing Middle Bill is still working its way through the Assembly, and it isn’t law yet. But the direction of travel is clear, and the appetite for compliant, income-generating second dwellings in Canberra is already there. For homeowners who don’t want to wait years for a renovation to shift the value or usability of their block, a container-based build offers a way to move now, within the existing rules, while keeping the door open to whatever the missing middle reforms eventually bring. Whether the goal is rental income, a place for university-aged kids, or independent living for ageing parents close to home, the combination of a fixed-size ceiling and a fast, largely off-site build is proving hard to ignore.