How to maximize affordability and sustainability through all-wood podiums
Architects are increasingly under pressure to create structures that are not only beautiful, functional, and safe, but also are less costly and faster to build. Wood podium construction takes an age-old material and moves it into the 21st century: Structures retain sought-after features—beauty, familiarity, carbon sequestration—while achieving greater heights and sometimes dramatic cost savings.
Mid-rise podium construction, consisting of two to five residential stories of wood framing above a concrete nonresidential first story (the “podium”), is common throughout North America. However, by using wood instead of concrete for the podium itself, designers can further reduce overall construction costs and time, while creating a more sustainable and less massive building.
Lower Cost
In several recent projects, use of wood building materials has yielded cost reductions and faster installation, resulting in significant economic savings. For the Galt Place affordable senior housing complex in Galt, Calif., for example, designers estimate they saved more than $1 million through lower material costs combined with soft-cost savings from faster construction, easier handling, and fewer trades on site. Similarly, for Oceano at Warner Center in Woodland Hills, Calif., a 244-unit apartment complex, the wood podium came in at two-thirds the cost of a concrete podium.
Simpler Installation
An all-wood building enhances construction in many ways. Field modifications of a wood deck away from the beam line are easier to accommodate because it is not necessary to X-ray the slab for rebar and/or post-tensioned strand placement. In addition, fewer building materials decreases the number of trades on the job and, as a result, mobilization time and construction delays. The redundancy of building each floor with the same trade and materials also improves framing efficiency and decreases the amount of detailing required by designers.
Structurally Sound
Wood’s long-standing prominence in residential projects leads some to believe it is incapable of meeting the needs of taller, mixed-use structures, but engineered beams not only offer the strength and durability for more high-demand applications, they bring about their own set of benefits. For example, a wood podium’s lighter weight is an advantage in high seismic zones where building mass affects lateral design loads. The wood podium design also allows some projects to use light-framed shear walls on the first level, as well as smaller foundations than would be sized for a concrete podium.
Sustainability
Wood is the only structural building material that grows naturally and is renewable. It also is biodegradable, non-toxic, energy efficient, recyclable, and reusable. When comparing wood to concrete, it’s noteworthy that cement production contributes up to 7% of worldwide CO2 emissions. While additives such as fly ash and slag can reduce the amount of cement in concrete, and thus its CO2 contribution, wood still has a significant advantage in this regard.
In addition, wood is unique in that more carbon is removed from the atmosphere by the growing tree than is emitted by its manufacture into products and transportation to its point of use, making it carbon-negative and thus a key material in the industry’s recent strides to reduce the embodied environmental impacts of buildings.
Additional Details
Despite its many benefits, wood podiums do bring about challenges, most notably a learning curve for the architect, engineer, and code official, and they require careful collaboration among the project team.
To learn more about the techniques and requirements of all-wood podium design, download "All-wood Podiums in Mid-rise Construction."
To read more about all-wood podiums and other state-of-the-art techniques and projects, become a member of APA Designers Circle at www.apawood.org/designerscircle. A free online community for architects, engineers, and other members of the commercial building industry, Designers Circle provides timely information, technical resources, continuing education, and recommendations for innovative wood-frame construction.
