Why is California Slow to Adopt Prefabricated Concrete Parking Structures?
Known for being one of the most innovative and progressive states in the country, California surprisingly falls behind in one area: adoption of prefabricated construction. Taking parking structures as an example, people choosing to park their car in one of the Golden State’s parking garages will only have a 4 percent chance of landing in a prefabricated concrete garage. This figure is far below the country’s average. According to the Precast/Prestressed Concrete Institute, depending on the region, approximately 30 to 55 percent of all parking structures nationwide tap into offsite construction for parking structures. The rest of the country has taken advantage of the benefits of prefabrication, but California has been slow to adopt, even when prefabrication is an ideal choice for the state’s unique seismic environment. Why has such a large and innovative state lagged in this area of construction?
To understand the lack of prefabricated parking structures in California, the rest of the market must be considered. Prefabrication’s biggest competition is traditional construction using cast-in-place concrete, a more common method where all construction takes place on-site. On the converse, in projects that leverage off-site construction, building elements are manufactured at a plant and transported to the construction site. In terms of parking structures specifically, there historically haven’t been many California-based prefabricated concrete companies that specialize in parking. This led to reliance on cast-in-place providers and an opportunity for traditional construction to build a reputation across the state by using just that: an appeal to tradition.
Cast-in-place had established a strong market share early on, so even when prefabrication in California started to take hold and move into parking, it was a struggle for many stakeholders to diverge from the way things had always been done. Today, this bias continues however, owners and developers who realize the benefits of off-site construction are increasingly asking for prefabrication on their projects.
In comparing cast-in-place and prefabrication, one of the most frequent misconceptions is that prefabricated structures are less resilient to seismic activity. In reality, prefabricated buildings and parking structures can utilize a Precast Hybrid Moment Frame (PHMF). The PHMF is classified as a special moment resisting frame and is governed by the California Building Code. The system provides functional resilience, going beyond code-required life safety to minimize structural damage and greatly improves the chances for immediate re-occupancy. This is invaluable to hospitals, government buildings and other essential services structures, and of high interest to owners or developers in areas with high seismic activity who are interested in protecting their building investment and tenants.
This type of lateral load resistant system is produced under factory-controlled conditions and connected using common construction methods and materials: rebar, post-tensioning steel and grout. Rebar and post-tensioning provide strength to the points of connection, while the rebar also acts to dissipate energy. Most seismic systems disperse forces through yielding. It’s not unusual for a building to permanently lean after a major earthquake which, in most cases will make it obsolete. However, the elastic, unbonded post-tensioning used in a PHMF is designed to overcome yielding and self-right the frame, and thus the structure, back into a plumb position.
Prefabricated parking structures with lateral load resistant systems, are truly resilient structures. With several seismic fault lines crisscrossing California, building seismically-resilient structures that are meant to withstand time is extremely important, making it even more baffling that precast prefabricated structures are not commonplace.
As prefabrication has developed over the last few decades, the industry has been able to offer faster, more efficient parking structures than cast-in-place providers. However, many Californians seem unaware of these benefits. Most have been trained to believe that construction is a long, grueling process that takes up space and resources. The option to manufacture much of a structure offsite is often overlooked, even though it can resolve many of the negative issues on-site construction has no way of overcoming. Moving labor off-site to a manufacturing plant results in less risk, reduced waste and delivers schedule and budget certainty. As an example, medium-to-large sized parking structures can be constructed significantly faster, saving time and allowing owners to use their asset sooner.
After a project is complete, prefabrication continues to deliver cost savings. A study published in the International Concrete Repair Institute, prepared by Walker Consultants, showed that “Cast-in-Place (CIP), Post Tensioned (PT) and precast structures showed a similar deterioration curve for the first 20 years, while the CIP/PT structures showed a higher cost afterward.” All concrete structures eventually need to be repaired, but prefabricated structures make maintenance easier and less destructive. Moreover, the research suggested that “it is expected and commonly accepted that cast-in-place concrete would have costlier maintenance and repair compared to precast concrete.” Prefabricated structures can hold up against California’s many types of weather and be easily and inexpensively repaired many years past assembly.
The prefabricated concrete community has already proven its unparalleled strengths in building parking structures made to last, and most of America has caught on. We hope to see greater adoption of prefabricated structures in the great state of California. Those who have already chosen to strategize with prefabrication have benefited from the efficiency and low maintenance costs, in addition to all the other benefits of off-site construction. California leads the nation in many areas and it’s time to fully embrace prefabrication in the built environment and catch up, or perhaps surpass the rest of the country.