Is Craning in Your Prefab Extension a New, Easier Way to Build?
Author: Julia Fairley Date Posted:6 March 2020
Should your next home be craned in using prefabricated modules? We spoke to five Australian and NZ builders to find out
There’s a kid on the construction block who, although not new, is making many architects and builders question if it could be a major future disruptor. Let us introduce you to prefabricated modular construction. Prefabricated homes have been around for decades. However, many architects and builders believe we are close to a tipping point where this construction method will quickly becoming the norm. Houzz talked to five architects and builders in Australia and New Zealand to get the real story.
Prefabricated and off-site modular construction is an alternative building method. It involves constructing large sections or modules of a home (if not the entire dwelling) off-site in a factory, then transporting the modules on-site to be installed, often using a crane.
It’s quickly gaining popularity in extensions and new builds, and while not every site or location lends itself to this type of construction, those that do can result in vastly more efficient projects.
Curious to find out if your next renovation or build should be modular? Find a builder near you on Houzz for an expert opinion
This type of building method favours materials that are quick to work with over those that are painstakingly laid one by one, hand by hand – goodbye, bricks and mortar; hello, steel framing and fibre-cement sheets. It is also better suited to larger mass-residential housing projects, such as high-rise apartments, than to smaller, individual residential homes.
Joe Snell, an architect and James Hardie ambassador, believes that in the near future whole sections of our homes will be constructed in a similar way to our cars – in a factory with a more rigorous focus on quality control and testing – before being transported on-site and connected together.
“We were hardly talking about prefabricated building 10 years ago, but now we are seeing projects hitting the ground,” says Snell. “In five to 10 years, I think prefabricated homes will feel common to the consumer, even if they aren’t in every suburb yet. In 10 to 20 years, I think the industry will have fundamentally changed and it will be normal for prefabricated homes to be viable – they will be winning the long-term race.”
“No rain days!” says Snell. “Almost every on-site construction program faces days of lost work due to inclement weather. It is a factor that can blow out timelines and budgets and illustrates the fact that developing something in a dry, well-lit and controlled environment, such as a factory, is more efficient than building out in a paddock, which is what a traditional home site is.”
For Matthew Dynon, architect and director of Sydney-based MODE Homes, centralised factories have the advantage of dodging local trade shortages that plague many traditional residential renovations and new builds. They also boast superior site access and ample space – not to mention security – needed to receive, log and store large deliveries of building materials and appliances.
“By building off-site, Cubiluxe is able to take away a large portion of building noise and disruption from neighbourhoods. Depending on the particular build, we have had clients who were able to stay in their home longer, as we began building off-site before we started the groundworks. Another advantage of our modular construction is that the structures are steel and engineered to be lifted, which makes them much stronger than a traditional build.”
The safety of homeowners’ trades is an often overlooked factor, but one that’s of vital importance to Cain. “We build second storeys off-site at ground level with free access around the entire building module,” he says. “This makes the work move quicker and improves work safety for our team, and by having better access it allows for greater quality control with detailed finishes.”
“Factory rent is a significant cost that needs to be accounted for,” says Dynon. “A traditional build does not need to consider this cost. Cranes and transport also add cost. But if module sizes are less than 3.5 metres wide while travelling these transport costs can be kept relatively low.”
Poor weather conditions can still affect installation, and architects and builders agree that in some cases, site access makes off-site modular construction impossible; think narrow roads or power poles getting in the way.
Snell addresses the elephant in the room, acknowledging that prefabricated and off-site modular construction can be restrictive in terms of style. “Good design can limit the aesthetic constraints that prefabrication poses, however for certain looks and bigger statements, a traditionally built house has more scope,” he says.
Snell believes this transition to factory and modular construction building – including the inevitable automated systems this involves – will put pressure on traditional building jobs unless professionals prepare for the change.
“It is imperative that Australia and New Zealand develop a world-leading prefabrication industry, otherwise we could see houses turning up on ships, as we have seen happen to our car and steel industries,” he says. “Prefabricated homes will have the biggest effect on volume builders, as the modular units have to fit on the back of a truck, limiting its use for bigger houses or rooms.”
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The answer to this question is highly variable, and many of the experts Houzz spoke with reported greater savings, greater expenditure and minimal differences when comparing traditional and modular building methods.
“Prefabricated homes are often more expensive than site builds, particularly when transport costs are included,” says Fiona McKenzie of Melbourne, Victoria-based Superpod. “It really depends on your comparison groups. I think mid-high end pre-built homes are cheaper than some site builds (such as bespoke architect ‘designer’ homes) and more expensive than others (such as volume builders’ homes). They tend to be quicker builds than site builds.”
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Cost savings come with scales of economy – a factor that can largely drive down prices of larger housing developments than individual residential builds. Nevertheless, “Because prefab is inherently more time efficient it will end up being more cost effective,” says Snell. “However, because the traditional method of construction is so established, and there are simply more companies offering that method, it is more competitive in most conventional home building scenarios for now. This is rapidly changing.”
It pays to keep in mind that the bigger the build you’re undertaking, the bigger the crane you’ll need. And the bigger the crane, the more expensive it will be to hire.
“For a simple lift where the crane is close to the truck and where the module will be lifted to a smaller crane, a 45-tonne crane may only be required,” says Dynon.
“These can be rented for the time required for about $1,500. If you’re lifting from the street over power lines and require a permit, the entire cost of the craning exercise could be over $10,000.”
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“Small streets and power lines pose some problems for craning,” says Dynon. “For new homes on larger blocks of land, the craning is very easy if the crane and truck can both be on private property during the lift. When lifting from the street or public realm, permits and street closures are required and can be difficult to obtain.”
But even if you can sidestep the need for a crane, trucks still come with their own challenges. Snell points out that trucks often have to take over-dimensional truck routes that avoid narrow streets, low bridges and power lines.
At Nautilus Modular, cranes posed enough of a challenge that Watkins found a way to circumnavigate them altogether. “The dimensions of our modules are such that we are able to transport them on a specially designed trailer system and stay within the transport envelope,” he says.
“This means we don’t exceed maximum transport heights or widths, or need pilot vehicles, or have restrictions on when we transport the modules on the road network. The trailers are designed in such a way that the module installation method on the sub-floor assembly structure doesn’t require craning in – installation can be achieved by two people.”
While the question of cost is still highly variable with prefabricated and modular building, there’s no debating that this approach significantly reduces timeframes. “What would be a nine-month job traditionally can turn into a six-month job using off-site construction,” says Cain.
For Jason Watkins, general manager of Nautilus Modular based in Wanaka, New Zealand, reducing time is a key future focus for the company. “Off-site manufacturing and prefabrication can allow a building to be constructed and completed on-site sometimes in a matter of days, whereas traditional methods are likely to take months,” he says. This is the best-case theoretical scenario. In current practical terms, this dramatically short timeframe is physically possible but it’s best not to count on it… at least for now.
“Our planned future plants will be capable of producing quantities of modules sufficient for multiple houses in one day,” says Watkins. “Installation of the modules on-site into a functioning building will only take a matter of days, so from production to installation, the total time for a build could be less than a week in total for a family house.”
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“Council approvals are much the same for both in terms of aesthetics, however some further approvals may be needed to get the modular units to site as they are relatively large for many streets and suburbs,” says Snell.
Watkins adds that off-site manufactured buildings are still constructed to the Building Code, but points out that councils’ assessment processes don’t always ‘fit’ off-site modular construction. “The challenge for councils going forward is that off-site modular builds will often have quite different processes and stages of production to traditional builds – how councils assess these buildings through their production phases is something I know local government authorities are working on,” he says.
Sustainability is a subject that’s equally difficult and important to quantify, regardless of building practices. “Good design has an understanding of the prevailing natural climatic conditions on any given site and on the best way to harness or block them out,” says Matthew Dynon. “Materials need to selected with sustainability in mind, from how that material is made or formed to how that material is used.”
Dynon embraces sustainable building practices at MODE Homes, using double-glazed windows and insulated floors and walls that exceed the standard requirements.
Watkins is also tackling sustainability by spearheading waste – a topic that’s caused heat in the construction industry. “We reduce waste through two main initiatives. First, we integrate standard materials and their dimensions into our design. For example, we decided that the width of our modules would be governed by multipliers of 1,200 millimetres as this is the width of a standard sheet of ply, which is one of our key materials. And second, we work with suppliers to produce components from raw materials exactly to the dimensions we require, so there are no off-cuts and minimal waste through the supply chain.”
“It depends on the size of the building,” says McKenzie.
“Large Superpod buildings can be designed to pretty much any shape or size. Smaller buildings are offered in particular sizes and shapes to enable easier transport and keep the costs of redesigning to a minimum. The same goes for interiors. You can fit out a Superpod Passivhaus any way you like, but for smaller homes we offer a pre-designed package, to save time and reduce redesign costs.”
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This method of building has lagged in Australia and New Zealand but has long been embraced in Europe – we’ve all heard about the precision and speed of German prefabricated homes. Nevertheless, many modular builders are experiencing an upswing in popularity and expect it to continue.
“They might have a bit more traction in the inner city (because access is difficult due to traffic) and remote areas (because access is difficult due to distance) and would continue to grow in my view in this space,” says McKenzie.
“We also need to remind ourselves how other things have progress in this way: once upon a time, a carpenter would build joinery from scratch, day after day, on-site; but we’ve progressed past that and we now accept that our kitchen will be built off-site, delivered and installed.”
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As with all large and small investments, doing your homework is key. “Make sure the process is very clear in regards to what the modular builder is offering,” says Snell of finding a builder who offers this construction method. “Are they a one-stop shop that creates the building in the factory, but also does the on-site requirements as well, such as site preparation, connection to services, delivery and building completion?”
Like every building method, the devil is in the details, and what may sound like a small difference in details can equate to a big difference in cost.
“Some companies only construct their own designs and those designs may or may not be what homeowners are looking for; others may only construct new builds and don’t want to know about renovations and extension,” says Cain.
Have you used prefabricated or off-site modular building methods? Share your experiences in the Comments below, like this story, save the images, and join the conversation.
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