Written by Laura Stock with contributions from Olivia Freese and Ryan Stumpf

For architects and clients seeking innovative tilt-up wall textures and details, the construction products that are available on the market frequently limit designs due to availability, cost, and/or construction feasibility. Because of these constraints, the team stepped outside of the box and looked toward customized 3D printing as a potential solution. 

When developing the lobby and monumental staircase designs, the architects aspired to feature raw materials and construction practices to create a space that would celebrate the natural elements of construction. By highlighting the exposed concrete slab with the steel staircase, glass handrail, wood wall panels, and open ceiling, a clean aesthetic was defined. The architects knew they wanted the exposed concrete wall to serve as the backdrop for these natural elements, but they needed some subtle detailing to tie it all together. The architect Tadao Ando and his methodology for cleanly exposing concrete construction techniques offered inspiration for how to enhance the natural and raw construction techniques without looking additive. But, the finish level and detailing of an architectural cast-in-place wall was not within the budget or schedule. So, the team determined that the efficiency and speed of tilt-up construction would be the best solution for creating this interior wall.

Whether utilizing cast-in-place or tilt-up construction, the substrate material is incredibly important as it translates the final texture to the exposed wall. This is where the team began their investigation process. When reviewing options, a smooth, imperfection-free look was determined to be the most important goal. After some research and discussion with the concrete contractor, the final solution was to use HDO plywood, which is a ¾” high-density overlay plywood substrate with an appropriate strength, tolerance, and texture. The next essential design item was to determine how to create clean joints between the substrate panels. The team utilized an extruded PVC reveal as a readily available and cost-effective product. The final detail was to create the void of the form ties. Actual form ties were tested as an option, but the small size and typical CIP-anchorage method were not ideal for this new tilt-up application, especially when considering how the pucks would be removed. The team scoured the market for other readily available products to recreate the voids desired for the design, but they could not find a competitive solution with comparable benefits. Thus, the idea of 3D printing our customized shape was born. Armed with available office printers and many spools of PLA, the team began creating interesting shapes for casting in this feature wall.

3D printing provided the design team with many advantages, including flexibility in the design, timing, and detailing, as well as material convenience. Using 3D modeling software, the team worked through many design iterations to determine which depths, diameters, spacing, and proportions would best emulate the desired CIP detail elements. This allowed the team to print the puck to the exact diameter and depth that was needed while also incorporating details to allow fastening to the formwork. Having the ability to control the timing as well as the material selection was also critical. It was determined that each 4’x8’ substrate panel would need six pucks spaced evenly and fastened to the surface. Each puck would be 2” in diameter at the base and taper to 1½” inches in diameter at the top, with various depths to be further explored.

Preventing the pucks from moving after rebar placement and during the concrete pour was a major challenge for the team. Using glue or screws were the two options for remediation, but when evaluating glue many concerns were raised, including how it would react to the heat and weight of the concrete. Utilizing a screw seemed like the most viable option, but the team knew it would need to be concealed within the puck so it would not be visible on the surface of the finished panel. To avoid this, a small cavity was modeled through the center of the puck to hide the screw fastener and ensure a smooth finish within the void. Due to the anchoring method and the need to confirm the depth of the puck, it became obvious that a practice print and mock-up pour was necessary.

Before printing for the mock-up pour could begin, it was determined that an understanding of various printing materials and filaments was necessary. To sustain the wear and tear of construction and the concrete-curing process, PLA was chosen as the 3D printing material because, as a thermal plastic polyester, PLA provided the necessary durability and heat resistance. The depth of the void was determined through the first mock-up. 

Timing was critical as the team considered which depth would provide the best design solution while also meeting schedule needs. Three options were investigated and printed. It took approximately ten hours to print nine, 1”-deep pucks; ¾” pucks took about eight hours; and ½” pucks needed six hours. Prior to installation, the construction team hand sanded each puck to create a smooth finish and allow for easy removal.

The mockup determined that the ¾” puck was the best option because it offered the desired look by providing enough depth for shadow lines and the eight-hour print time would allow the team to print two pucks each day. The puck material held up to the temperatures and the weight of the concrete, yet the construction team was challenged because they needed to prevent the attachment hole from translating to the final panel. A few methods were tested to cover this depression: Using one layer of red tape on the buried end of the puck to cover the screw hole was deemed insufficient for creating a smooth finish. Covering the puck with a release agent left a residue on the finished product that could not be removed and also did not hide the screw hole. 

The winning solution was to use two layers of tape, creating a smooth finish with no visible screw head. With size, depth, fastening details, and materials all addressed, the team was ready for construction.

The 3D printer’s 10”x10” glass-printing surface allowed the team to print nine pucks per printing session; each puck required about eight hours to print. With 252 pucks needed, the printing process was expected to take ten days. This timeline was much quicker than any other product lead time could have been, so the team was given the go-ahead to print. On-site review of the panels prior to pouring the concrete is standard for tilt-up construction; however, the team took extra caution to confirm locations and alignments, and extra care was taken when installing the reveals and the pucks. 

When the day came for the panel to be erected, the on-site crew and design team stood in anticipation. The team thought the reveals and the pucks would remain on the casting slab when the panel was tilted into place, but they were surprised to see almost all of the pieces remained cast into the wall, which did not occur during the mock-up process. Thankfully, the overall appearance of the concrete was exactly as the team had hoped.

There were a few lessons learned along the way. The team anticipated that the contractor would quickly remove the reveals and pucks after the wall was set and the concrete was still “soft.” This process should have occured within a few days of the panel lift. But, in reality, the pieces were not removed for months so they had to be drilled out, which was a time-consuming process that created spalling at the reveals and required patching of the concrete.

Once the panels were patched, the outcome was exactly as the team had hoped. The concrete is raw, yet crisp, and the CIP detailing is pleasantly featured. Any imperfections add to the character and nature of construction and the use of concrete in general. Both the design team and the construction team were thrilled with the final product.

The open communication between the design team and the concrete contractor proved invaluable from the beginning of the design to the end of construction. The designers conveyed their desired outcomes and means of construction, while the contractors provided important information about products, means and methods, and realistic expectations. The control both parties demonstrated throughout the entire process paved the way for a beautiful outcome and an impressive piece of work. 

Working as a team throughout the design and construction process helped the architects and the contractors establish standards for the future. The 3D printing process showcased multiple means of efficiency, flexibility in design, and timely solutions. Knowing and understanding the process of printing and installation provided an additional layer of efficiency, which is an important aspect of any construction timeline. The team is incredibly proud of the use of 3D printing, and the knowledge gleaned from lessons learned will be instrumental in the future. One of the best rewards of this project was recognizing how 3D printing could compliment tilt-up construction so harmoniously. The team can’t wait to test more ideas for future projects soon.

Precedent Photos:

Tadao Andō Langen Foundation

Construction Photos: Design Team

Final Photos: Sam Fentress