I’m writing this in a building with 756 windows.

I know because I counted, and spent months researching, measuring, designing, 3D printing, and assembling them for the final project of an architecture course I took last spring.

I’m a computer science major, but I make a point of taking a few non-math non-CS courses each year, made possible by Brown University’s Open Curriculumn. Last semester, those courses were in architecture and epigraphy; this blog post is about a project for the former.

I’m referring to the CBR Building in Brussels. The best-known work of Belgian architect Constantin Brodzki (1924–2021), it was commissioned by Cimenteries Belges Réunie, a Belgian cement company, to serve as both their corporate headquarters and a demonstration of the versatility of concrete. Brodzki was given full access to their factory and worked for nearly a decade to develop the concrete molding process.1

This then-novel construction technique allowed the building to go up at a record speed of one floor per week; a billboard on-site proudly recorded the time each floor took.

Furthermore, the glass was embedded into the cement modules in the factory, protecting the floors from the elements and allowing work to progress on the interior as floors above were still under construction. The orange glass, one of the building’s most distinctive features,2 is custom “stopray” glass produced by Glaverbel,3 whose circular offices were just across the chaussée from the CBR Building. The reflective glass helped regulate the temperature of the building, which was the first air-conditioned (office?) building in Belgium.

Brodzki, and his friends—famous mid-century furniture designers Jules Wabbes and Florence Knoll—designed custom furniture and interiors, which were preserved when the building was converted into a coworking space in 2018.4

***

Brodzki drew inspiration, not from modernism, but from Art Nouveau, especially admiring the work of fellow Belgian Victor Horta. In fact, he viewed modernist superhero Le Corbusier with disdain: “Le Corbusier’s view of things mattered more to him than the comfort of people. He scoffed at the subject of water, trees, and the sun as if they had never existed before him.”535–36

A tight integration with nature was always a priority for Brodzki. The CBR Building was designed to be “strongly rooted” in the ground, its flared base imitating tree roots.

The building is in a leafy Brussels neighborhood of mostly mid-century office buildings.

Like many architects, Brodzki had a personal view of utopia that informed his buildings. Brodzki was concerned by overpopulation and the continued expansion of humans into the natural world. “By destroying our environment,” he felt, “we ultimately destroy ourselves.”537

“Moreover, only a part of the terrestrial surface is reserved for humans. Everyone lives in a kind of national park in reverse, outside of which nature develops in complete freedom.”538

This dichotomy of the natural and the engineered is present in the CBR Building; the seemingly-natural curves of the building are in fact less natural than they might appear.

The seam between floors is a perfect sine wave, and the oval shape of the window is a precise mathematical shape called a superellipse (or “squircle”). Given the building’s precise prefabricated form, I wanted to follow in Brodzki’s footsteps by reverse-engineering the shapes instead of tracing them.

A perfect match!

After trying a bunch of squircle equations, I landed on a²x²y²r + 1 = x² + a²y², where a controls the aspect ratio and r the corner radius.6 It produces continuously curved squircles (i.e., have just one critical point) that match the windows perfectly.

As a break from all that math, I made a paper model using the 2D modules I designed. It would’ve worked better with thicker paper and double-sided tape, but having even a flimsy physical object early on provided a burst of motivation.

Now that I’d finished the building in two dimensions, it was time to model it in a third. I downloaded a few gigabytes’ worth of 3D modeling software, but eventually settled on Autodesk Fusion, which I have access to through my university.

With only a little bit of pain, I was able to import my 2D designs from Figma and clean them up. The part I was most worried about—creating the elegant curved shape—was actually one of the easiest. I used the “Loft” tool to smoothly connect the edges of the shapes.

Et voilà!

Once I had the most common module design (the landlocked “center-center” piece), I mangled it into the remaining eight variants.

***

My model relies heavily on 3D printing, which I feel honors the spirit of the prefabricated nature of the building’s facade. I modeled the modules in Autodesk Fusion and converted them to 3D printer instructions using PrusaSlicer.

This is a good time to mention the Brown Design Workshop, an incredible student-run space I’m a member of with woodworking, machining, welding, and sewing tools—and vitally, three laser cutters and a dozen 3D printers.

I did most of my struggling with beginner CAD here at midnight while students across from me built a fucking car from scratch. I’ve used the BDW in the past for less impressive things, such as literally putting a notch in my belt.

***

Corporate wants you to find the difference between these two pictures:

The one on the left has a 0.15mm layer height and takes seven minutes to print. The one on the right has a 0.05mm layer height and takes half an hour. The larger the layer height, the fewer layers there are and the faster it is to print.

At a 0.05mm layer height, it would take hundreds of hours to print all 756 modules. I was able to incrementally improve on this, cutting my print time by about:

• 25% by balancing quality and speed and settling on 0.07mm as the thickest acceptable layer height, instead of the minimum of 0.05mm.
• 30% by using newer (and less well-known on campus, thus less busy) Prusa MK4S printers in the Granoff Center’s7 Physical Media Laboratory, as opposed to the BDW’s MK3Ses.8
• 30% by using a variable layer height. The parts of my print that did’t have curved sections could be printed more quickly at the maximum layer height of 0.3mm.
• 25% by hollowing out the window instead of my previous plan of separately-printed orange snap-in inserts. This was suggested by my architecture professor and made my model both more realistic and easier to assemble.

In the end, I was able to cut my print time down to just a third of my original estimate. It took me only a week to print everything I needed, usually producing four to six batches a day,9 a handful of which failed for one reason or another.

Sometimes this happened.

***

I completed two side quests during this project.

After discovering a photograph in Constantin Brodzki, Architecte showing the CBR company’s logo as a large cement sign outside their building, I decided to model and print it. To make the “C” stand up without support, I shifted its center of gravity by making one side solid plastic.

I also noticed curved cement chairs in pictures of the building and decided to print them too. While they fit the building’s aesthetic quite well, they are actually far more recent and were not designed by Brodzki. I tracked them down to a street furniture company called Magourban, though they remind me of the work of Swiss designer Willy Guhl.

Now, back to the regularly scheduled programming.

***

While the modules in the actual building slot together, mine are flat on the back and glued to a foamcore box wrapped in reflective orange vinyl. Because foamcore is difficult to cut precisely by hand, I looked to the Brown Design Workshop’s laser cutters.10

With the right settings, the laser cutter would allow me to cut foamcore panels with pinpoint (laserpoint?) precision and perfectly straight lines. With the wrong settings, the laser cutter would melt the foam and set the paper on fire. After experimenting with settings, I arrived at the right combination that minimized melting. The key was to do two passes with a lower-energy laser, giving the foam a few seconds to cool in between.

Figuring out the laser cutter settings was sometimes-smoky trial and error.

The laser cutter was so precise that I was able to have it make two kinds of cuts—one, through both paper layers and the foamcore, and another that left one paper layer intact, allowing me to create a clean join between sheets of foamcore. I assembled the laser-cut sheets into three boxes (the two wings and the central core) with hot glue, added wooden interior dowels to counteract warping, and attached the boxes together with bolts.

I covered the boxes in orange reflective vinyl—meant for wrapping cars—and attached the 756 facade modules using superglue gel. To cover the roof and core, I printed thin plastic veneers using the same material as the facades. (I hadn’t accounted for these veneers in my measurements, which led to some imprecision.)

***

From late-night CAD sessions to early-morning printer checks, what started as an assignment became something closer to an obsession.

I’ve realized I really enjoy building things with my hands; I’m already planning to get metal- and woodworking certified at the BDW next semester. (When AI comes for my job, maybe I’ll follow my calling into the trades.)

I think the CBR Building is underrated. Fifty-eight years later, it still looks genuinely futuristic without feeling cartoonish. When I visited, the lobby was busy and alive, revitalized with 21st-century amenities: a co-working space and a coffee shop serving frappés and breakfast.

Brodzki’s building looked towards the future, and now, thrives in it.

Thanks to Eliot for accompanying me to Brussels, and taking the picture of me just above; Professor Dietrich Neumann for his course, Contemporary Architecture; the Brown Design Workshop and the Creative Arts and Technology Spaces of the Brown Arts Institute for access to hundreds of thousands of dollars of equipment; and the BDW’s student monitors for their passion and expertise.

Footnotes

1. While working on the CBR Building, he constructed two prefabricated test buildings—a dining hall and a research laboratory—at the company’s plant in Lier, Belgium.

   ↩

2. In researching Brodzki and his building, I came across several artistic tributes to the building:

   • Rotor DC, a Belgian group that helps deconstruct historic buildings, preserved the original orange stopray windows when they were replaced during a 2018 renovation, and has made them available to architects and artists;
   • Brussels-based ICI Architectes used one in their renovation of a home in Uccle, Belgium.
   • Fotomuseum Antwerp exhibited several windows from the CBR Building in 2023, also sourced from Rotor DC.
   • Marc Thomasset, a Belgian graphic designer, featured the CBR Building in The Brutalist Colouring Book.
   • The 1818 Collective sells the $1,200 “Brodzki Mirror” in the shape of the CBR Building’s window modules (available in brass, nickel, and walnut finishes).

   ↩

3. The high-speed Eurostar I took to Brussels had Glaverbel windows. ↩

4. Constantin Brodzki’s son Alexandre, himself an architect, lead the fight to list the building in a historic registry, saying in an interview (translated from French): “My fear is that the soul of the building […] will be completely distorted. All the elements—the furniture, the window frames, the floors, the carpets—all of it was designed from A to Z as a total work, and all the elements were revolutionary.” ↩