Structural steel and concrete buildings have been part of American city skylines for more than a century. But today, these traditional building structures are giving way to a new crop of innovative construction methods that offer stakeholders myriad benefits—shorter construction timelines, improved sustainability and, perhaps most importantly, reduced construction costs.
This shift is especially timely given the impact of trade tariffs and a shortage of skilled workers in the construction industry. In fact, U.S. Labor Department data from October 2018 reveals the cost of construction materials increased 7.4 percent over the previous year. Given this, now is an optimal time for the industry to explore alternative construction methods that reduce structural costs and improve margins.
Two techniques at the forefront of this movement are hybrid and prefabricated construction. While both have the potential to reduce construction costs without risking building quality or durability, it’s important for project owners to fully understand the benefits—and possible tradeoffs—of these systems. If you’re considering one of these systems, here’s what to keep in mind:
This construction method integrates precast concrete and poured in place concrete, as well as other materials, like structural steel. It’s ideal for mid-rise buildings ranging from seven to 12 stories; these projects offer more flexibility in material choice, unlike, for example, a high-rise building that requires poured-in-place in concrete. Key benefits include:
Reduced Material Costs and Jobsite Waste
Hybrid structural systems often require less building materials than all-concrete buildings, which means reduced material costs. For example, a common hybrid system includes precast hollow-core slabs combined with steel or pour-in-place concrete.
Decreased waste is an additional benefit of hybrid systems utilizing precast concrete. Because precast concrete is factory-made often using exact-batching technology, there is little waste created in the plant, and less construction and jobsite debris.
Because a hybrid system often requires off-site manufacturing of prefabricated elements like precast concrete, labor needs at the construction site are reduced.
Sustainability is a hallmark of hybrid structural systems. Concrete offers improved energy efficiency because it absorbs and releases heat slowly, shifting air conditioning and heating loads to allow smaller, more efficient HVAC systems. In addition, insulation is often used in architectural panels and sandwich wall panels to increase thermal efficiency. According to the National Precast Concrete Association, this can result in savings of up to 25 percent on heating and cooling costs. In addition, precast concrete easily accommodates recycled materials, like slag and fly ash. Lastly, new concrete material technology called ultra-high-performance concrete (UHPC) is stronger and lighter than the previously available technology. Manufactured without conventional steel reinforcing bars, the self-reinforcing concrete uses fiber reinforcement instead. Projects using this technology can generate up to 75 percent fewer greenhouse gas emissions than conventional concrete.
Keep in mind a hybrid system can be more complex than a traditional poured-in-place concrete project given the use of additional materials. Additionally, this complexity can lengthen the construction timeline. Owners can offset this by selecting a general contractor with experience managing a hybrid system construction. But overall, given the potential to offset rising material costs, this system can be a smart choice for mid-rise developments.
Circa 922, a luxury apartment building in Chicago’s West Loop neighborhood, is an example of a property that utilizes a cost-competitive hybrid system. During the pre-construction phase, my firm vetted various hybrid systems, ultimately selecting the Girder-Slab system because it provides the benefits of concrete at a reduced cost. In fact, on average, a Girder-Slab system costs 25 to 30 percent less than other structural systems. In the case of Circa 922, the system not only reduced the cost of construction, but also reduced the schedule and sped construction up onsite. This increase in speed in tandem with the lower material costs led to savings totaling more than $1 million—a portion of these funds were then reinvested in the property to create additional value and a higher investment return for ownership.
Prefabricated construction, also called off-site or modular construction, increased in popularity following the last recession. During the downturn, many skilled laborers left the construction industry and did not return, leaving developers seeking workarounds to labor shortages. Prefabricated construction is an ideal solution because the structural system is built in a factory and transported to the construction site. This construction method typically consists of cold-form steel, metal stud or wood framing. It is ideal for building heights of seven stories or less. Benefits include:
Prefabrication costs are typically lower than site-built costs because of manufacturing efficiencies, shorter construction timelines and the need for fewer skilled workers at the jobsite.
Accelerated Construction Timelines
In many instances, prefabrication takes less than half the time of traditional construction. For example, my firm erected the sub structure at Kelmscott Park, a luxury condo community in Lake Forest, Ill., in 20 days using prefabrication—traditional construction would have taken twice as long. This is due in part to the elimination of onsite weather factors and subcontractor delays, as well as quicker fabrication because multiple pieces can be constructed simultaneously. At Kelmscott Park, the general contractor’s involvement during the pre-construction phase meant less surprises once construction began, making it possible to achieve an accelerated timeline.
Improved Quality Control
When you prefabricate in a controlled manufacturing setting and follow specific standards, the components of the structure are built to a uniform quality. Furthermore, these components are built by experienced workers in a weather-resistant factory where quality checks are regularly conducted.
Although there are few downsides to prefabrication, close cooperation between the owner, architect and general contractor from project onset is critical. This is because prefabricated system requirements must inform building design to ensure success during construction. As such, an experienced general contractor that can guide the architect through the system’s requirements during pre-construction is imperative.