An Ancient Concept Reborn

An Ancient Concept Reborn

“Stereotomy” is defined as a descriptive geometry, but the word represents something that is practically a lost art. It is the art (and science) of designing and building by cutting stone blocks into complex, close-fitting shapes that are specific to the project being constructed. A curved wall, for example, is made up of stones that are cut to the curve and the radius lines, sized and shaped to fit together with high precision. It is a very old form of masonry, but in a sense it is the opposite of the more familiar modular masonry, where a basic construction unit such as a brick is used to create all the shapes of the structure, approximating curves and angles as needed.

Justin Diles, Assistant Professor of Architecture at the Knowlton School of Architecture, Ohio State University, wants to bring stereotomy into the 21st century. Composites And Architecture talked to Diles about his winning entry in the TexFab competition, entitled Plastic Stereotomy.

The “plastic” in the title is both an adjective and a noun. “It refers to both plasticity of the design methods I used, and to the material plastic,” says Diles. Stereotomy made of plastic, or more specifically, plastic composite.

“If you think about domes and arches made out of individually cut pieces of stone designed to fit with each other,” explains Diles, “I and other young architects have been interested in how digital fabrication could revive this tradition of close-fitting elements. There was a tradition of learning the forms. All of that knowledge is lost. But I think the concepts are being revived by digital technology. I think I’m the one of the few people right now looking at the way FRP and composites could actually be a way forward for reviving these old techniques.”

Plastic Stereotomy is an enclosure, the creation of a space, but not a fully-walled room. It is made of just 12 pieces, designed to assemble in an interlocking fashion. They are irregular – very irregular – in shape, and range widely in size. Although they are made in an FRP sandwich panel design, they are not thin in the way FRP panels are typically designed. The foam cores range from 8” to 18” thick, making the pieces more like carved blocks than like shells or panels.

They are, in fact, carved solids, pieces of EPS foam that are milled to shape on a large CNC router.   Then the EPS blocks themselves are covered in FRP composite. No molds are needed. (In the composites industry, this kind of fabrication is thought of as “surfboard technology,” although the computer-controlled foam-shaping for Plastic Stereotomy somewhat more advanced and complex than the work done in most board shops.)

Plastic Stereotomy is the outgrowth of a project made by Diles two years ago, a free-standing wall made of interlocking FRP pieces held together only by friction. “I’ve been exploring that system,” related Diles recently. “I figured out how to make a wall with that system. The next problem, as an architect, was to figure out how to use slotted components to make lightweight, nested, and interlocking components that could make a room. It was important for me that it not be read as a sculpture, but as an architectural prototype.”

The software system that Diles developed for the wall project, and used for Plastic Stereotomy, is at the heart of the design. “A lot of us architects use the same software. There’s this trend: the way that the digital model is subdivided gets translated directly into the panelization of a structure. In the digital model, a complex surface is composed of triangles, so you end up with a building that’s composed of triangular panels. I’m looking for patterns that don’t exactly coincide with the ways they’re represented in a computer.”

“The panels needed to interlock,” he continues, “so I developed this patterning, which appears in my wall piece and reappears in Plastic Stereotomy, that enables me to explore this idea of interlocking. It’s an algorithmic process that produces these patterns. You deform a surface in two different ways and overlay them. That yields moments where the surfaces cross, and intersections produce a pattern. It’s based on wave deformation.”

(Not unlike the interference patterns produced by two point wave sources that you may have seen in a wave tank in high school physics.)

“I use Finite Element analysis software,” continues Diles. “I buckle these surfaces, that produces a sinusoidal deformation pattern in the surface. You can see both waves in the surface, but I don’t combine them, I superimpose them, and that produces the pattern that you find.   I created a catalog of these things. The first pass, I just find patterns I like. The second pass I work with them, I come back in as a designer and develop them so they have construction logic.”

The design he came up with won the TexFab competition. The win includes having his entry executed in the real world by Kreysler & Associates, a leading fabricator of architectural composites (and sponsor of this blog.)

Upon consultation with the fabricator, Diles made some modifications to the design. “The pieces have become larger and fewer, but the formal language is still the same. Plasticity refers to the formal language of the project, but also to the procedural method.” Diles’ design software could, essentially, be turned up or turned down in terms of the number of parts and the complexity of each. “The winning design then became a proposition that was further explored through the act of making it.”

The final piece is currently under construction in California. It has a surface area of 1060 square feet. It has a pie-shaped footprint 16’ long, 8’ wide at its widest point and 5’ at the narrowest part. The interior has a minimum 6’7” clearance, and is 7’ high at its tallest point.

The wall thickness varies, as mentioned. “The design of the interior surface is not just an offset version of the exterior surface, and vice versa. They’re each designed to their own requirements. The interior is designed to be a cool space to be in. On the exterior, there’s more variation of the surface modulation. There are two different colors, black, and what may be silver. The dark pieces are flat, the silver pieces are curved. On the interior, they’re more smooth.”

The finished project will be shipped unassembled to Texas and assembled on site at TexFab, where it will be on display. There are also plans to exhibit it at the Composites Pavilion at the AIA Convention in Atlanta, GA in May.