It seems like we are hearing more these days about the advances being made in what is variously called modular or prefabricated construction. Yet this is not such a new idea. Is it that prefabrication is now an idea whose time has finally come?
This article shows that it is – that prefabrication is no longer just a viable alternate construction technique, but is increasingly being integrated into mainstream construction.
First, what do we understand by the concept of modular or prefabricated construction? Answers may vary according to the context and one’s perspective. For the purposes of this article, we adopt the very broad definition used by PrefabAUS – the peak body for Australia’s off-site construction industry – which describes prefabrication as “any part of a building that has been fabricated at a place other than its final location”. Other terms include: Off-site Construction, Modern Methods of Construction, Modular, Unitised, Volumetric, Panelised, Kit of Parts, and Flat Pack. System-Built is another term used in the USA. Fundamentally, ‘fabrication’ is taken to denote something more than simply the preparation of building materials into their customary form such as dimensioned timber; fabrication occurs, for example, when the timber is assembled into roof trusses.
Let’s set the scene by outlining what we might think of as the Construction Method Continuum. At one end of this continuum is entirely on-site construction. An interesting, and for the time not uncommon, example of this is the Byramine Homestead built in 1842 (it’s on the Murray Valley Highway between Yarrawonga and Cobram if you are wondering). With household security a concern of the time, Byramine’s bespoke design elements include an octagonal-shaped central room affording excellent views all around – especially helpful in case of attack – as well as very low height door handles to allow small children ready access in case of danger, and concealed entry to the substantial cellar for refuge.
Emphasising the on-site orientation of this project, the construction program first entailed building a kiln on the property to make the bricks for the homestead. Pine felled from the property was fashioned into the ceilings, beams, floors, shutters and shingles. Finishing touches like window panes and door furniture would likely have been sourced from much farther afield – apparently the nearest home at that time was in Melbourne!
Fast forward to today, and at the opposite extreme of the Construction Method Continuum lies wholly off-site prefabricated construction, delivered to site for connection to services. As an obvious example we might think of the ubiquitous office sheds so familiar on building sites, characterised by utilitarian design and basic creature comforts. Being robust, portable, reusable and economical, they have proven to be particularly well suited to these temporary applications.
Where is prefabrication now?
In between the two extreme examples cited above, the continuum encompasses an array of almost limitless degrees of prefabrication, some of which are already commonplace in modern construction. Increasingly, practical, robust and scalable prefabrication options are being added. This may be illustrated by the following examples of off-site fabrication, all of which are already being adopted in Australia.
- Modular services units for an otherwise conventionally constructed office tower. These units are pre-installed with the requisite electrical, hydraulic and mechanical components and are transported to the site once the building core is complete and lifted by crane into the risers designed specifically to accommodate them.
- Built up and fully fitted bathroom pods for delivery to apartment buildings and hospitals, where they are lifted onto each floor of the building, located in place, and connected to pre-designated services points.
- Flat-pack floor, wall and roof panels delivered to project sites for rapid assembly into completed buildings (typically by a team from the manufacturer).
- Complete modular homes lifted by crane into position and fully finished apartment modules which are trucked to site and lifted by crane and stacked into place on otherwise conventional base building elements (which may include lift core, stairs, car park and podium as required).
Today, substantially prefabricated projects have been undertaken in Australia for a diverse range of projects, including houses, weekenders, medical clinics, hotels, low rise apartment buildings, fast food restaurants, university student campus accommodation, community halls and school buildings (not the portable classrooms of old), a variety of display suites for residential development projects, suburban railway stations, and even an RSPCA animal shelter.
What are the benefits of prefabrication?
- Shorter project delivery timeframes resulting from the ability to run concurrent, rather than sequential, construction programs;
- Reduced project funding costs;
- Reduced materials wastage during construction;
- Increased construction precision through manufacturing-style fabrication;
- Reduced need for rectification works;
- Reduced effects of adverse weather, which doesn’t impact on factory production;
- Reduced impact on site, (access requirements, dust and noise);
- Improved operational documentation (‘as-built’ and installed product information);
- Reduced maintenance costs; and
- Scheduling efficiencies when site access is problematic.
What about the disadvantages?
The disadvantages of modular construction were easier to identify in the past, when rigid design parameters and ‘boxy’ dimensions were commonly-cited criticisms. Some performance teething problems around the new technologies, and the fact that the earlier applications were often for low cost solutions, also didn’t help the general perception of prefabricated projects.
Such shortcomings are quickly receding with flexibility now a key feature. For example, the design elements and ‘look and feel’ of the bathroom pods are indistinguishable from conventionally built apartment bathrooms. Finish quality, however, can be consistently higher. So rather than striving to become as good as a conventionally built finished bathroom, these prefabricated units are now capable of raising the quality standard.
Maximising the benefits from off-site manufacturing processes has typically involved volume production. However, the entry thresholds have become much more manageable. Continued improvements in technology, processes, and supply chain management now mean that the economical threshold for prefabricated bathroom pods is just 30 units. For an office tower project, prefabrication of the services shaft already compares favourably with the alternative of progressive installation as the building core is completed. Somewhat counter-intuitively, prefabrication of very small volume projects, including a variety of one-off projects, are being successfully undertaken in the education, hospitality, healthcare, residential and transport sectors.
Although not a disadvantage in itself, it is important to recognise that incorporating more than an incidental amount of prefabrication works into a project does necessitate a revised approach to the way the project is conceived, initiated and delivered as outlined below. And one of the consequences of faster delivery schedules is that there is less time to ‘catch up’ when something gets behind, so much more of the project planning and design needs to be established up front.
The way forward for prefabrication
As is often the case with new products, systems or methods, the questions that are raised can be more obvious than the answers. Intuitively appealing answers are in ready supply. Hard evidence to support a business case is less plentiful, especially in relation to performance assessment and lifecycle benefits, such as reduced maintenance costs. How have the completed projects performed? What lessons have been learned?
While there is still much to be done to systematically evaluate the full extent of the benefits, it is apparent (as noted above) that adoption of prefabricated elements can demonstrate tangible benefits – reduced construction timelines compared to the conventional build alternatives and reduced disruption to an operational site being the easiest to identify.
A key enabler of the increased application of prefabrication has been the significant investment undertaken by a variety of players in the prefabrication space to enhance design solutions and the optimisation of structural integrity for transport, lifting and installed use, as well as in manufacturing processes and supply chain management.
Another is the increased take up of Building Information Modelling (BIM). By extending electronic design into detailed drawings, that can be shared and worked on by the consultants and contractors on the project (and ultimately the building owners and facility managers), BIM facilitates design being more fully resolved and provides confidence that the on-site works and prefabrication elements will tie in as intended. This is crucial to the successful incorporation of prefabrication. Incompatible intentions for the installation of the various services components by the services contractors can be a common issue.
Under BIM, such clashes arise at the digital drawing stage and thus can be addressed early in the design process, rather than at the ‘roughing in’, or worse, even later in the build. The happy co-existence of the various services components within minimally-sized risers and ceiling cavity spaces is one way that BIM and prefabrication can combine to improve design efficiency and project costs. With Australia being one of the leading adopters of BIM, this should continue to provide impetus for prefabrication.
Project management considerations
Adaptation of the project management function is required where substantial prefabrication is involved. In particular, the work program will require re-weighting to reflect the increased coordination and planning involved at the earlier stages of the project. When done well, this will result in a commensurably reduced project management commitment in the latter stages of the project. The increasing technical and economic viability of prefabricated construction raises the following obvious questions.
- How should the client go about identifying and assessing the potential advantages of incorporating prefabrication elements into their project?
- How is the business case for the project altered, including bank funding implications for prefabricated elements, as well as payment certification processes throughout delivery?
- What are the design implications? In particular, how is the design development process to be optimised to exploit the flexibility and benefits afforded by the latest developments in prefabrication? Can prefabrication make sense when the design development assumes in-situ construction?
- How does prefabrication impact on the procurement method to be adopted, including for the prefabrication company? What about the appropriate form of contract to be adopted for the project and its prefabricated elements?
- At a more fundamental level, ‘site meetings’ can take on a different dimension, with works at the project site becoming just one part of the overall work program. Assessing and monitoring progress will entail the project team also visiting component manufacturing locations.
Prefabrication has quietly but steadily moved from being a ‘specialty’ alternative method of construction to becoming increasingly complementary to the broader construction industry. It is now poised to make further inroads.
By incorporating the right elements of prefabrication, the right way into a project, significant benefits can be yielded for owners and developers alike. However, recognition of the suite of implications, especially the increased concentration of project management, architectural, consultant and client engagement in the early stages of the project is vital. Otherwise, the prospective benefits to the client may be dissipated or entirely foregone.
Examples abound of the progressive introduction of prefabrication that are now so commonplace that we no longer recognise them as such – ready mix concrete, metal framed windows delivered to site already painted and glazed, tilt/precast panels and air conditioning ductwork come to mind. That plasterboard has largely replaced lath and plaster can be seen as just another example of the pervasiveness of prefabrication.
When viewed this way, what we are seeing is a natural and pragmatic evolution. Even so, it looks now that we are entering a period of exciting advancement, featuring across a wider range of building components, becoming more sophisticated and higher value, and increasingly integral (rather than ancillary) to the building structure. And at the same time, the prefabricated elements are becoming less and less discernible in the end product, so that the construction method no longer rigidly defines the final outcome.
The advances in prefabrication mean that question has changed; it is no longer whether prefabrication makes sense or not for a project, but rather how much and which prefabrication elements should be incorporated. And, just as importantly, how is this to be accomplished most effectively on a given project?
Prefabrication – coming to (or already part of) a project near you. If you haven’t already considered how prefabrication can advantage your next project, now would be a good time to start.