Custom fabrication for more appealing affordable housing

Huskey Truss Facility

Huskey Truss Facility in Tennessee

Recipients of the AIA Innovation and Practice in House Design Research Grant investigated the potential to increase architectural expression and create efficiencies in custom fabrication of wood structures

Digital fabrication technologies and their impact on architectural practice is a growing topic of conversation. Powerful and proven custom fabrication abilities drawing on both digital and handcrafted methods have long existed in construction. In the custom timber home industry, digitally controlled saws and routers produce precut kits for heavy frame and mass timber houses. Wood truss manufacturers produce inexpensive custom trusses that rationalize complex geometries and structural loads providing framers with formworks that make multifaceted roofs easily constructible. Yet, these complex roofs rarely add significant spatial interest to the buildings they top. Geometric complexity is the enemy of affordable construction, a truth that often yields the assembly of unimaginative boxes.

As recipients of the AIA Innovation and Practice in House Design Research Grant, we sought to find ways to apply existing custom fabrication abilities to the design of small, inexpensive, light wood framed houses. Our end goal? To unlock new opportunities for architectural expression and space making in the affordable housing market.

We began our research touring manufacturing facilities, interviewing truss designers and manufacturers, exploring software capabilities, with the hope of identifying barriers to success and opportunities for enhanced collaboration throughout the design and build processes.

Manufacturing plants are, of course, driven by goals of profit and efficiency. Considered “truss designers,” those responsible for determining lumber layout for assembly are guided by computers and driven by supply and demand. The goals of design customization are inherently at odds with those of an efficiently-operated manufacturing plant, but the technological capabilities of the facilities we visited proved that there are many ways truss designers are creating efficiencies. For example, the production of light wood packages from 3D files and use of automated jig tables permit quick assembly of distinct trusses. Sophisticated technologies like engineering software that maximizes lumber efficiency and assists assembly cut down on labor needs, minimizing error and waste and increasing the cost-effectiveness of expensive machinery.

We found this value difficult for the designer ­­to access, and even more so for the client. Our conversations also revealed a common disconnect between the architect and truss designer. We found that very rarely do the two communicate early in the design process, if at all.  The resultant production inefficiencies could have implications for quality and client satisfaction.

Considering these and other challenges of working with a manufacturer, we developed a design case study with the intention of producing highly customized trusses and determining potential application in affordable housing. We selected a design based on desired spatial and light qualities and complexity, which came from a variety of unique trusses and sloping ceiling panes with metal plates.  

Issues of design complexity turned out to be inconsequential due to powerful software capabilities. Our biggest problem was effective communication between the architect and the manufacturer as well as a lack of engagement from the software provider. Driven solely by metal plate sales, software providers found little motivation to assist architects with learning their software. The most capable software remains proprietary and Revit plugins available for architects come without instruction or customer assistance. Our case study unfortunately led us through months of troubleshooting with little assistance.

Once we established a successful workflow for converting and transferring 3D models, we acquired estimates from two parties: a small components manufacturer with minimal automation and a manufacturer with a larger and more automated facility. We hoped to engage with a highly automated facility, but the selected larger facility was not taking one-off projects at the time. The difference between the two estimates was significant, but we did not conclude that the cost difference could be attributed to automation capabilities alone. We found that the more automated the facility, the more flexibility the manufacturer has in choosing projects to accept and reject. But the fact remains that custom projects are less profitable for manufacturers than those with many multiples of identical trusses.

As automation makes its way into smaller manufacturing plants, where the truss designers enjoy engaging with architects to complete small projects, the promises remain for affordable custom work.

The AIA Innovation and Practice in House Design Research Grant is a joint program of the Housing Knowledge Community and Small Project Practitioners Knowledge Community. Tricia Stuth, FAIA, Ted Shelton, FAIA, and Christina Bouler, Assoc. AIA, received the grant in 2016.

AIA is committed to empowering architects to use and engage in research. Learn more here.

Image credits

Huskey Truss Facility

Curb Studio

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