Bay Area landscape studios team with local artisans to evolve CNC-fabricated site elements.

By Sarah Cowles

Alcatraz keeps disappearing, but not because of sea-level rise. “Alcatraz Island has been stolen, replaced, and stolen again,” says Nicholas Gotthardt, a senior associate at Surfacedesign in San Francisco. The irresistible Alcatraz is one element of a large topographic model of San Francisco’s Golden Gate headlands that anchors the visitor overlook at Fort Point National Historic Site, where Surfacedesign was part of a team that designed new site amenities completed in 2014.

The model, made of finely detailed precast concrete, is a literal touchstone at the overlook, which offers dramatic views to the Golden Gate Bridge and San Francisco Bay, as well as a rest stop for cyclists and hikers. Gotthardt recalls the impetus for creating the model: “We wanted to design an interpretive piece that wasn’t signage and words. We wanted something tactile—something people could touch.” Gotthardt had honed his digital modeling skills in the fabrication lab at the Ohio State University’s Master of Landscape Architecture program. With the Fort Point project, he found an opportunity to apply those skills, including fabrication using computer numerical control, or CNC, at the site scale. “The idea of a pancake topo model as the centerpiece of this small urban space came from the officewide comment that ‘We should build more models!’ There isn’t always the time or resources in practice to get into physical modeling the same way that you get to do in school.”

Today both undergraduate and graduate landscape programs provide training and facilities in CNC fabrication, including five-axis mills for sculpting wood and foam, 3-D printers, and laser cutters. Yet this new generation of graduates, facile with the work flow producing CNC models in the design studio, often finds it difficult to ply these skills once they reach the world of professional practice. But a handful of studios in the Bay Area are leveraging the technical and aesthetic know-how of this cohort, and in the process are building relationships with local fabricators to handle the complexities of converting digital models to full-scale site elements in concrete, stone, and even rammed earth.

To create the Golden Gate model, the team at Surfacedesign began by assembling open-source GIS topographic and bathymetric data of the region. The team “stitched” these digital elevation models together into a triangulated mesh in Rhino, the 3-D modeling application. To improve legibility of the model, they used Rhino’s tools to convert the mesh to a conventional “pancake” topography model.

The next steps involved coaxing the digital model to meet the realities of production. In CNC concrete casting, the digital model represents the “positive,” which is used to test the proportion and detail of the model. In this process of working with 1:1 foam mock-ups, the team decided to exaggerate the vertical scale of the model. Next, they milled a mold from the revised positive and began testing color and finishes using 1:1 transects, or slices, of a 10-foot-long model. Additional steps included milling a foam mock-up of the model including the cast-in-place elements to test the proportions of the model in its installed state. The finished model features an inlaid stainless steel waterline to define the shoreline.

Across the bay in West Berkeley, the team at Groundworks Office is partnering with Concreteworks, a custom fabrication shop in Alameda, to prototype a furniture element for San Francisco International Airport’s new Terminal 1 on the arrivals promenade. The unit, which combines seating and plantings, echoes an oculus element inside Terminal 1, designed by the Bay Area architects Kuth Ranieri. “We developed a number of shapes that referenced this form,” says Brennan Cox, ASLA, a founding partner of Groundworks. “And while it’s impossible to say where the form was birthed, on paper or the digital environment, we refined it through digital methods and computer modeling algorithms.”

Staci Betsch, a designer at Groundworks, developed a “family” of four elements to create small gathering spaces along the concourse. She used Rhino to craft a model using one precast mold to create two forms, one with a cutout for a wooden seating element, the other as a planter void. The beauty of their initial quarter-inch-scale mock-up caught the interior architects by surprise, Cox says: “It was smooth and curvilinear, borderline irresistible. And today, it is a focal point for the redesign of Terminal 1.”

With the architects on board, Cox contacted Mark Rogero at Concreteworks to begin production tests: “We immediately utilized their capabilities and understanding of the fabrication process to develop the furniture element. The transition from design to fabrication was seamless because they worked in Rhino as well, so it was a simple matter of e-mailing them our design files,” Cox says. Rogero’s specialists helped Cox finesse the model to meet production tolerances and adjusted the mirrored elements of the form so that fabrication would require only one mold.

In Richmond, California, just north of Berkeley, is the expansive American Soil & Stone operation. What began as a humble bulk materials and specialty soil mixing yard (think the Chez Panisse of mulch) now features a range of CNC cutting tools for stone. The head of sales, Jim Spahr, describes what drove his company’s decision to invest in the technology about 10 years ago: “We first bought saws to fix things that came in incorrectly from overseas, because if a piece is wrong, it takes a long time for the piece—up to 14 weeks—to be replaced. We expanded to additional bridge saws, and now the majority of what we do is custom and special order, and only 15 percent [of the work] is repairs.” The capital investment has paid off, as more landscape architects gain expertise in CNC work flows and can take advantage of the equipment. “The CNC division went from loss leader to one of the most profitable in the company,” Spahr says. The company’s mix of commissions is about 40 percent from landscape architects, 25 percent from building architects, and the remainder from general contractors and homeowners.

As with the work flow for CNC concrete casting, landscape architects must work closely with shop technicians to refine the digital model to fine-tune for production in stone. At American Soil & Stone, that expert is Francisco Arriaga, who hails from a family of traditional masons. As Spahr describes Arriaga, “He is a real maestro. He can make anything out of any material. He taught himself the technology and has the know-how to repair the machines to avoid downtime. Francisco knows a lot more than our clients, and calmly talks to them, to show them what the stone can and can’t do.”

Spahr emphasizes that project mock-ups are key to the process of working with designers and owner-builders. “We’ve also learned we need to do a small mock-up, then do a larger piece down the way. Masons and installers make sure they can install it, and field verify measurements from the person who is actually putting it up on the wall.”

Even rammed-earth constructions can be designed and fabricated using CNC technology. At TLS Landscape Architecture in Berkeley (I was a landscape designer at this office when it was called Tom Leader Studio), Erik Prince, ASLA, designed and prototyped a rammed-earth bench for Stanford University.

The site at the gateway to the Stanford School of Medicine featured two heritage oaks, providing a shaded spot for gathering. Prince imagined an earthen but sophisticated element to anchor the space and support a range of seating and reclining positions. As Prince describes, “It was important that these two large benches hold the space, complementing the oak but becoming a bench that encourages people to sit together, be social, sit in different postures—lying down or sitting up.” Prince had seen a mock-up of a CNC-formed wall for a vineyard at Watershed Materials in Napa, California, and was eager to test the technology in a site application: “We toured the shop and learned about the ability for rammed earth to use any locally sourced aggregate, even directly from the actual site, evoking a true regional materiality with a wide range of gradients.”

In the studio, Prince modeled the bench in Rhino and then “sliced” the model into sections to make foam templates of the mock-up: “Once we had a good profile, we did a 1:1 mock-up using blue foam. We tested two conditions of the bench and calibrated the geometries based on comfort factors, how it felt using the bench in different situations.”

In the end, the mock-ups and the renderings of the bench proved too exuberant for the client, despite the design’s being within their budget. Prince hopes that the studies and mock-ups will be useful in demonstrating to future clients the possibilities of the materials and the process.

Sarah Cowles is a Caucasus-based artist and writer documenting landscapes in transition. She is the 2018 Kashkul Artist in Residence at the American University of Iraq, Sulaimani.