A 20ft two-bedroom granny flat on a trailer chassis

The base unit is a standard 20ft expandable container house — approximately 37m² expanded — but this one had three specific add-ons that pushed it beyond the entry-level specification.

Trailer chassis with dual axle: the client's block is large and relatively flat, which made a trailer configuration practical rather than a fixed slab. The dual-axle trailer means the unit can be repositioned if needed and doesn't require council approval for a permanent foundation. This was a deliberate choice, not a cost-saving shortcut — the client specifically wanted flexibility.

PU (polyurethane) foam insulation panels: Melbourne gets cold. Not Hobart cold, but cold enough that standard EPS panels would have meant real heating bills and uncomfortable winters. PU foam has a lower thermal conductivity than EPS — the same panel thickness delivers meaningfully better performance. For a home where someone is sleeping and living year-round, this was the right call.

Custom L-shaped kitchen cabinetry: the kitchen in the photos isn't a flat-pack kit installed on-site — it was built and fitted at the factory before the unit shipped. High-gloss white door fronts, a three-drawer bank, overhead cabinets, a grey stone-effect benchtop and a black undermount sink. The client chose the layout and finishes during the design phase. When the unit arrived in Melbourne, the kitchen was already there.

The client's specific configuration — 20ft unit, PU insulation, trailer setup and custom cabinetry — landed at approximately $38,000–$45,000 all-in, covering the unit, ocean freight to Melbourne port and inland trucking to the property.

That does not include utility connections. Getting water and power connected requires a licensed electrician and plumber regardless of where you put it. Budget another $4,000–$8,000 depending on how far the services need to run from the main house. The client used their own plumber for this part.

For context: a comparable two-bedroom granny flat built on a concrete slab by a Victorian builder would typically run $150,000–$220,000 and take 10–14 months. This project was quote-to-delivered in under four months.

This is the question everyone asks, and it's the right question to ask before you commit to anything. Trailer-mounted versus permanent structure makes a significant difference under Victorian planning law.

Because this unit sits on a registered trailer rather than a fixed foundation, it is classified differently from a permanent secondary dwelling under Victoria's planning scheme. In many cases — particularly on rural-residential and large suburban lots — a trailer-mounted configuration used for ancillary family accommodation doesn't trigger the same full Development Application process that a permanently placed granny flat would.

That said, Victoria's rules are not uniform. The local council and the specific zone your property sits in will determine what's required. Before this client ordered, they called their local council planning department, described the unit and asked directly. The answer they got was that on their specific lot — zoned General Residential, above the minimum lot size threshold — the trailer-mounted configuration was acceptable as a temporary or ancillary structure for family use.

This outcome is not guaranteed to be the same on your property. If you're considering a similar setup in Victoria, call your council first. It costs nothing and takes half an hour.

For clients who do need a Building Permit, Haven supplies the full documentation package: SAA electrical certification, WaterMark plumbing documentation, a structural engineering certificate and an NCC compliance statement. These are the documents your certifier or council will ask for, and they're included as standard with every Australian-specification unit we ship.

Kitchen: the L-shaped layout makes proper use of the corner space. There's actual bench space for food prep, real cabinetry with drawer storage, and the sink sits in the wing of the L rather than the middle — a better layout than many apartments twice this size.

Living area: the open-plan living room has multiple windows on two walls, which is what makes it feel liveable rather than cramped. Natural light from the morning sun on one side and afternoon light from the other.

Bedrooms: two separate rooms, each with a window. The dark SPC flooring runs consistently through both — it's waterproof, hardwearing, and looks considerably more expensive than it is.

Ceiling: the flush ceiling panels make the 2.4m height feel taller than it is. No exposed beams, no industrial look — just a clean, finished residential space.