The introduction of large scale prefabrication methodologies is transforming Australia’s building services industry, producing quality, programming, productivity and safety benefits.
Services riser prefabrication methodologies are in place in Europe and North America. It is only now that this approach is being accepted more readily into Australia.
Following extensive overseas study tours and consultation with external suppliers, structural engineers and principal contractors, specialist mechanical subcontractor A.G. Coombs been pioneering their application in the local construction market, which sees these prefabricated services risers make use of a number of technical innovations:
- Extensive use is made of 3D computer aided drafting (CAD) and building information modelling (BIM) software to optimise riser design and ensure coordination with other systems and the building fabric.
- Every riser frame is specifically designed and engineer certified for its application to ensure it will safely withstand the additional stresses placed on it during transport and lifting.
- Risers include a number of proprietary design features that facilitate site installation and attachment to minimise site installation activities and accommodate relative movement between the building structure and the services systems.
- Service and maintenance platforms and access features are designed and built in to remove the need to construct these in the shafts on-site, and to provide improved safe future access.
“The installation of services risers in high rise buildings typically presents the single biggest health and safety risk for the project,” said A.G. Coombs strategic development director Bryon Price.
In a large building, services risers can be made up of thousands of parts typically installed one component at a time with lengths of duct, pipework, and components such as valves and service platform elements placed, joined and fixed by tradespeople working in the shaft.
Traditional installation requires teams from various trades including ductwork and pipework installation contractors, mechanical, fire and other specialist services, electrical installation, lagging contractors and other personnel to work off cantilevered scaffolds, increasing the risk of falling from height and exposing them to potential injury from falling materials. Additional risks include potential slip/trip/falls and musculoskeletal injury from the storage and movement of materials on each floor deck prior to installation. Post-installation system testing can also require further work in the risers.
“With prefabricated services risers, air conditioning, ventilation and specialist exhaust ductwork, fire protection and other building services features are pre-installed in an engineered three-storey frame,” explained Price. “This work is carried out in an offsite dedicated prefabrication factory and the riser sections are delivered to site and lifted into place.”
The riser sections are secured in the riser shafts with fastenings that can be installed from the floor deck, further reducing the need for multiple trade teams to work at height. The requirement to move riser components on the floor decks is also eliminated.
A leading example is underway at Sydney’s landmark Barangaroo South development. A.G. Coombs has been working closely with developer and principal contractor Lend Lease on the introduction of prefabricated services riser methodology for the 43-storey Tower 2. This is the first time pre-fabricated risers have been used in a high rise building in Australia and is part of Lend Lease’s focus on safety as its number one priority.
The traditional approach for Tower 2’s four 43-storey high risers would have been to install over 8,000 services components one piece at a time in the large vertical shafts with the attendant working-at-height risks, fall of materials and the related slip/trip/fall hazards associated with the manual handling of materials prior to installation. The use of pre-fabrication on this tower has eliminated the need for more than 4,000 hours of high risk and complicated site installation work.
The prefabrication of the riser frames in a factory environment has also delivered significant quality improvements alongside the safety outcomes. Ductwork and pipework is factory pressure tested across the three-storey sections resulting in far fewer joints to site test, and again further reducing time working at height.
Prefabrication methodologies are also now being applied to plant rooms and the major central plant, and importantly are now also being successfully applied on horizontal services runs. This is particularly effective on large scale low rise projects like hospitals and shopping complexes where this methodology is leading to productivity and programming benefits together with the further elimination of working at height risks. The significant reduction or even elimination of the need to carry out oxyacetylene welding is a further benefit and safety enhancement.
“On major building projects, these prefabrication methodologies result in the transfer of thousands of hours of complicated site installation into a controlled factory environment, with the need to work at height in risers virtually eliminated,” said Price.
He admits that changing current industry paradigms, however, is always challenging.
“For example, the adoption of prefabricated services risers requires changes to the way high rise building construction is ordered and organised. Previously, typical services riser installation followed the construction of the building upwards with multiple services trades continuously working below and tracking the forming up of the floors and shafts overhead. The arrival of the risers in prefabricated three-storey sections creates new programming challenges around construction management and crane scheduling.” he said.
Other challenges include changes to formwork system design to allow the installation of prefabricated riser sections from above and the fire and smoke rating requirements of shafts which raise technical and constructability issues.
“Site installation management arrangements need to reflect a strong understanding that this is a new approach for Australian construction sites,” said Price. “The degree of consultation, project planning and pre-lift/pre-installation site coordination and communication must reflect this understanding, and the need to minimise the risks associated with new processes.”
However, Price says that simply replacing on-site installation with off-site fabrication achieves only part of the potential.
“Preplanning for prefabrication, and then properly considering in the building and systems design stage the opportunities that prefabrication and the associated modularisation can offer, is essential to fully realise all the benefits that off-site fabrication can bring,” he said.
“This new approach to services installation has very significantly reduced construction risk on recent major projects. It also brings substantial additional benefits to high rise construction and services installation ensuring that it will continue to be considered and applied on these projects. Combined, the safety and other benefits mean that prefabricated services risers are set to become an industry standard in Australia and this will make riser installation significantly safer across the industry.”