If you have only ever built on site, the idea that a home can go from bare slab to watertight lock-up in around five days sounds like marketing. It is not. It is how prefab panelised homes have been built across Europe for the last thirty years, across thirteen countries, and how they are increasingly being built in Australia.

This post walks through what actually happens in those five days, what happens in the months before, and where the real savings come from — because the headline timeline only makes sense once you see the full operational picture.

Why timeline matters more than most builders track

Time is the most under-priced cost in Australian residential construction. The bank charges interest on the construction loan every month. Site supervisors and project managers are paid by the week. Insurance, scaffold hire, security, temporary fencing, portable amenities — all of it accrues for as long as the site is open.

For developers, the cost is even sharper: a finished home sitting in the market is earning rent or sale proceeds; a half-built home is burning capital. Every month of build time is a month of negative cash flow.

A standard new build in Australia typically takes nine to twelve months from slab to handover. A panelised prefab equivalent runs around three to four months. The two-thirds reduction is not magic — it comes from moving the precision work into a factory while the slab is being poured, so the two streams of work run in parallel rather than sequentially.

What happens before anything arrives on site

The visible part of a prefab build — the five days on site — is the small tip of a much bigger iceberg. Most of the work happens in the months before the first panel is craned.

Design adaptation. Whether you are bringing your own architect’s plans or working from one of our reference designs, the first step is adapting the design to the panelised system. This is engineering work — making sure the wall, roof and floor cassettes can be cut, transported and assembled while still hitting your performance targets.

Energy modelling. Net Zero Plus runs the design through thermal modelling so we know what the finished home will perform at. Wall R-values typically come in at 4-5, roof and floor systems at R 7, and windows at U-values of 0.8-1.2. We confirm star rating and, if relevant, Passive House compliance before anyone cuts material.

Engineering and certification. Full engineering drawings — often running to hundreds of pages — are produced. This sounds like overkill compared to a typical Australian local build’s documentation, but it is what allows the factory to cut and assemble panels to millimetre precision. It is also what gives builders and developers documentary confidence that what arrives will be what was specified.

Factory production. While the slab is being poured on site, wall panels, roof cassettes and floor panels are being assembled in the factory. Triple-glazed windows are installed in the wall panels. Airtight membranes and waterproof barriers are applied and inspected. Conduits for electrical runs are pre-installed inside the walls.

Transport. The completed panels are loaded onto 40-foot containers and shipped to the construction site, working with experienced customs brokers to handle the logistics.

By the time the panels arrive, the site team’s job has changed from “build a house” to “assemble a kit”. That is a much faster and lower-risk job.

The five-day on-site sequence

What follows is a typical sequence. Real builds vary based on size, site access, weather, and crane logistics — but the broad shape holds.

Day 0: Slab ready, panels in transit

The slab has cured and been surveyed. Setting-out lines are marked. The crane operator is briefed. Containers arrive on or near the site, ideally with a hardstand close enough that panels can be lifted directly from container to position. A small crew — typically four to six people including the crane operator — is on site.

Day 1-2: Walls go up

External wall panels are craned into position and bolted to the slab according to the setting-out plan. Each panel arrives complete: structural timber frame (KVH structural timber, kiln-dried and strength-graded), continuous insulation, airtight membrane on the inside, waterproof barrier on the outside, and the triple-glazed window already installed in the opening.

Because the connections between panels were engineered in advance, the on-site task is locating and fixing — not measuring, cutting, or improvising. Internal load-bearing walls go up in the same sequence. By the end of day two, the external envelope is largely complete.

Day 3-4: Roof and floor cassettes

Floor cassettes for upper levels (if applicable) are craned in next, followed by roof panels. Like the walls, these are pre-engineered assemblies with insulation and weather protection already integrated.

The roof is the moment where the build feels most different from a conventional site sequence. There is no rafter cutting, no on-site insulation install, no fascia work in the rain. The roof panels arrive sized to the engineering, and the install crew lifts, locates and fixes them in sequence.

Day 5: Watertight lock-up

By the end of day five — sometimes earlier on simpler designs — the building is watertight. The external envelope is sealed. Windows and doors are in. The roof is on and weatherproof. Internal services rough-in can start the following day, in an environment that is dry, secure and shielded from weather.

That is the moment where the prefab story starts to compound. Every internal trade now works in a building that does not care whether it is raining outside. Plasterboard goes up faster because the studs are straight. Electrical pre-installed conduits speed up first fix. Tile-and-fix can run earlier because finishes are not at risk from weather.

What you avoid by building this way

The headline savings are visible — five days of crew time instead of months of framing and roofing. The deeper savings are less obvious:

• Weather delays. Most of the build is now indoor work in an already-watertight envelope.
• Subcontractor sequencing problems. With trades arriving into a sealed building, the cascading delays where one trade waits for another are dramatically reduced.
• Rework from on-site mistakes. Factory-cut panels do not need to be adjusted with a circular saw at 4pm on a Friday.
• Material theft and damage. Materials live in a factory, not in skip bins on a site, until the day they are installed.
• Insurance and finance carrying costs. A three-month build accrues a third of the carrying cost of a nine-month build.
• Trade scarcity exposure. A panelised build needs fewer site trades, fewer days, which means less exposure to the labour market every time a project goes to programme.
  
  

Where the timeline savings actually come from

The honest answer is that prefab does not make any single step faster — it makes the steps overlap. While the slab is curing, the walls are being built. While the walls are being built, the roof is being built. By the time the slab is ready, the walls and roof are ready too.

A site build has to do these sequentially because the carpenters, the roofers, and the slab crew are largely the same people working in the same place. A prefab build separates them spatially. The factory does what it does best — repetitive, precise, weather-independent work. The site does what it does best — slab, services, finishes, handover.

For developers running multiple builds, the parallelisation compounds further. A portfolio of ten houses on ten sites can have ten sets of panels in production at the same factory, with site crews rotating through lock-up sequences instead of being tied up at single sites for months.

When prefab is and isn’t the right choice

Prefab is at its strongest when:

• The site has reasonable crane access
• The design can be resolved early (changes after panel production are expensive)
• Performance targets matter (Passive House, 8+ star, healthy home)
• Build timeline has a real financial cost (developer cash flow, owner rent paid elsewhere)

Prefab is harder when:

• Sites are tight, sloping, or hard to crane onto
• Designs change repeatedly through construction
• The build is a small addition to an existing structure rather than a new dwelling
• There is no engineering capacity to resolve details up front

Most projects fall in the first category. The second category is where panelised prefab probably isn’t the right tool — and we will tell you that during the feasibility conversation, not three months in.

Frequently asked questions

Is “slab to lock-up in five days” realistic in Australia? Yes, for a typical detached home or duplex with good crane access. We have seen it done. Larger or more complex builds extend the timeline but the structure of the sequence stays the same.

Who does the on-site assembly? Your choice of qualified local builders, an owner-builder, or a builder we can introduce you to. The panels come with full engineering documentation, so any competent builder can install them with our support.

What happens to the build programme if there is a delay? Most “delays” we see come from finishes, not structure. Once the building is at lock-up, weather no longer matters, and trades work to standard programmes inside a sealed envelope.

Do we need a special crane? A standard mobile crane is sufficient for most residential builds. We work with the site team on lift planning before panels are dispatched.

Will the local council accept prefab construction? Yes. Our panels arrive with full engineering certification to meet relevant Australian standards. We have not had a council reject a properly documented prefab build.

Ready to see the numbers for your project? Get a free quote within 48 hours — or explore how this approach works for developers and builders.