Portable home vs shipping container vs traditional build
Last updated: 2 September 2026
A purpose-built transportable modular home is usually the best balance of delivered cost, speed and habitable comfort for adding a second dwelling to an existing property. A shipping container conversion is cheapest to buy and genuinely strong and stackable, but pays for it in internal width, ceiling height and thermal performance once you make it liveable. Traditional on-site construction costs the most and takes the longest, but gives unlimited design freedom, the easiest match to an existing house and the most conventional lending and resale position. Roomi builds transportable modular buildings, and we have written this to be useful even if you choose one of the other two.
Comparison at a glance
Cost and timeframe figures below are industry-wide market ranges for Australian projects, not Roomi quotes. Roomi's own pricing is quoted per project and is available on request. The site-built granny flat range is sourced from thegrannyflatguide.com, 2026.
| Factor | Transportable modular | Shipping container conversion | Traditional on-site build |
|---|---|---|---|
| Typical delivered cost | Generally below site-built for an equivalent finish. Roomi pricing on request. | Lowest entry cost for a basic shell; rises sharply once insulated, lined, serviced and certified as habitable. | $110,000 to $300,000+ turnkey in Brisbane, roughly $2,500 to $4,000 per m² (market range, thegrannyflatguide.com, 2026). |
| Time from order to move-in | Weeks to a few months. Factory build runs in parallel with site preparation and approvals. | Weeks for a basic fit-out; longer if structural engineering is needed for large openings. | Commonly several months to a year, weather and trade availability dependent. |
| Insulation and thermal performance | Insulation designed into the framed wall, floor and roof cavity from the outset. Roomi includes split system air conditioning as standard on its models. | Weakest starting point. Steel is highly conductive with no cavity as delivered; good performance is achievable but must be added deliberately. | Best potential ceiling, because the wall build-up, glazing and orientation can all be specified without constraint. |
| Ceiling height and usable width | Designed to residential proportions. Roomi's standard widths are 3.5 m, 4.0 m and 4.5 m, with lengths from 8 m to 15 m. | Constrained. A standard container is about 2.4 m wide externally, and internal insulation and lining reduce both width and height further. | Unconstrained, subject to planning rules and budget. |
| Finish quality | Consistent and repeatable, built under cover without weather exposure. | Varies enormously with the converter. Excellent work exists; so does very poor work. | Highest ceiling for bespoke detail and for matching an existing house exactly. |
| Relocatability | Designed to be craned and transported. Loads wider than 3.5 m require pilot vehicles. | Excellent. Built for freight handling, and stackable. | Not practically relocatable. |
| Resale and lending | Usually valued as part of the property when fixed and approved, though non-standard construction can narrow lender choice. | Narrowest lender appetite and the thinnest resale market of the three. | Most conventional for valuation, mortgages and buyer expectations. |
| Council approval path | Building approval required. Designed to the National Construction Code, so a familiar path for certifiers. | Building approval required. Often needs additional structural engineering once openings are cut. | Building approval required, plus planning approval where not compliant. The most familiar path of all. |
Where shipping containers genuinely win
Container conversions get dismissed too easily, so here is the fair case for them. The shell is already a certified structural box, engineered for stacking and for sea freight loads, which is a lot of strength for the money. They are inherently secure and vandal resistant, which matters on remote or unattended sites. They are the easiest of the three to move repeatedly, and standard sizes mean predictable transport logistics. For a studio, workshop, site office, farm accommodation or storage-plus-amenity building, a well-executed conversion can be the most sensible spend on this page. The trade-offs are real, but they are trade-offs, not disqualifiers.
Where traditional construction genuinely wins
If you need the new dwelling to look like it was always part of the house, traditional construction is the only route that fully delivers it: matching the roof pitch, the brickwork, the eaves and the window profiles. It also handles awkward sites that a transport route cannot reach, sloping blocks that suit a suspended floor, and multi-level or unusual footprints. Valuers and lenders understand it without explanation. If your block has no truck or crane access, the decision is largely made for you.
Where transportable modular wins
The structural advantage is the build environment. Framing, wiring, plumbing, lining and cabinetry happen under cover, in one continuous run, with no rain delays and no trades waiting on each other across weeks. Site preparation and approvals proceed at the same time rather than afterwards, which is where most of the calendar saving comes from. You also get a fixed scope before work starts, which reduces the variation risk that inflates on-site projects. The constraint is honest: the building has to fit on a truck and be liftable, so its width is bounded and it must be delivered to a site a crane can reach.
Which buyer each option actually suits
- Choose transportable modular if you want a compliant, habitable second dwelling on a suburban or rural block within months rather than a year, you value a fixed scope, and your site can take a truck and a crane.
- Choose a container conversion if budget is the binding constraint, the use is a studio, office, workshop or short-term accommodation rather than a long-term family home, security matters, or you expect to relocate the structure more than once.
- Choose traditional construction if the extension has to match the existing house closely, the site cannot be accessed by transport or a crane, the design is complex or multi-level, or you want the most conventional possible valuation and lending outcome.
One thing that applies to all three. Whichever you choose, the building is only part of the cost. Site preparation, footings, delivery or crane hire, council and certifier fees, and water, sewer, stormwater and power connections sit on top. Compare quotes on the delivered, connected, approved number, not the shell price.
Frequently asked questions
Is a shipping container home cheaper than a transportable modular home?
To buy, usually yes, because the shell already exists. Once you add insulation, lining, wiring, plumbing, reinforced openings and habitable certification, the two often land closer together than the headline prices suggest.
Why do shipping container homes get hot in Queensland?
Steel is highly conductive and a container has no insulation cavity as delivered. Good thermal performance is achievable, but it costs either internal width for insulation or money for external insulation and cladding.
Which option is easiest to get council approval for?
All three need building approval. Purpose-built transportable and traditional construction are the most familiar to certifiers. Container conversions are approvable but often need extra structural engineering once openings are cut.
Can you get a home loan for a transportable or container home?
Lending is easier where the dwelling is fixed to the land, approved and valued with the property. Relocatable or non-standard construction is more often financed as an asset rather than through a standard mortgage. Lender policy varies, so check with your broker first.
Is a transportable home lower quality than one built on site?
Not inherently. Factory construction suits consistency. Traditional construction wins on unlimited design freedom and matching an existing house. The real difference is flexibility, not baseline quality.
Which option is best if I might move house?
A purpose-built transportable or a container conversion, since both are designed to be lifted. Budget for the true relocation cost: crane or tilt tray, permits, pilot vehicles for wide loads, and new footings and service connections at the destination.
Want the transportable option priced properly?
Roomi builds Class 1a transportable buildings in Salisbury, Brisbane, in lengths from 8 m to 15 m and widths of 3.5 m, 4.0 m and 4.5 m. Tell us the site and the space you need.