AAC Creates New Opportunities for BAC

The finished installation.

The goal of the Masonry Variations exhibit at the National Building Museum was to push classic materials like stone, terrazzo and brick into new, never-before-tried directions. But a fourth material, Autoclaved Aerated Concrete (AAC), had a head start. This very modern material inspired bold experimentation in the exhibit, which in turn provided a splashy U.S. debut for the material.

Designed to open future opportunities for masonry construction, the exhibit, which ran from Fall 2003 until Spring 2004, also demonstrated that the future of design depends on collaboration between the architect and craftworker. Each team was asked to “push the envelope” of masonry design.

The final organic shape called for skillful cutting and shaping techniques to achieve the desired curves found throughout each of the towers.

The tricky part of the selection process was choosing the AAC team, since it intrigued many of the designers. In the end, Winka Dubbeldam, principal of Archi-tectonics in New York City, drew the assignment. “We work with a lot of concrete, so it seemed to be a perfect fit,” she says.

Dubbeldam, whose work includes national and international projects, became familiar with AAC as a building material in its most traditional sense while working in Europe. The new direction she wanted to investigate was whether its unique flexibility could assemble a lightweight and organic architectural solution. She also wanted to explore a sensory characteristic often associated with lightweight architecture – sound. “Light architecture in the past often meant music, such as music pavilions,” she says.

The architect/craftworker team behind the dramatic AAC installation was Winka Dubbeldam of Archi-tectonics (NYC) and Bob Mion, IMI Regional Training Director for the Mid-Atlantic Region & Region 2 and a member of BAC Local 3 NY.

Sound and its organic representation ultimately served as a primary component of her design, through which she sought to merge a visitor’s understanding of architecture with an acoustical experience.

Ironically, while AAC represented the lightest of the exhibit materials, the high impact installation, named “Soundscapes,” filled the exhibit space from floor to ceiling and resulted in the heaviest structure. Still, to the credit of the architect, craftworkers and materials, the nearly 20-ton double tower installation resulted in a graceful, inviting, and intriguing structure.

In addition to collaboration, another lesson learned from Masonry Variations is how standardized training allows an architect to “push the design envelope.” In the case of “Soundscapes,” two teams of craftworkers worked on the project at two different training locations, a feat made possible by BAC and IMI’s national training system.
Similar to Jeanne Gang’s Stone “Curtain” (BAC Journal, May/June 2004), the successful completion of “Soundscapes” depended on testing the material and the construction methods. The impressive mass of “Soundscapes” early on required BAC craftworkers to rapidly apply newly learned information about the material and its construction efficiencies.

Each of the 27 courses of AAC was treated like its own floor plan. The larger of the two towers was built at the IMI National Training Center.

Construction of “Soundscapes” began in May 2003 at the IMI Training Center in New York City, led by Dubbeldam’s craftworker collaborator Bob Mion, the IMI Regional Training Director for Mid-Atlantic Region & Region 2 and a member of Local 3 NY. The initial team of craftworkers, led by instructor Henry Louie built a 4 ft-high sample that would ultimately be part of the final project. Of the many challenges facing the team, the most pressing was developing a method for cutting a rectangular building material into a final organic shape. “Each course of AAC was treated like its own floor plan,” explains Mion. “The final assembly depended on the ability to correctly align and stack one course on top of the other, and the ability to remain true to the architect’s design while achieving structural integrity.” With 27 courses for each of the two AAC towers, this process was extremely critical to the overall design and the tight construction schedule.

After about six weeks, the NYC team was ready to share their insights and techniques with a second BAC craftworker team led by instructor Dave Bellucci at the IMI National Training Center in Maryland. Bellucci took the methods learned in New York and trained a second team. To distinguish the work being done by the two IMI training centers, the two towers were nicknamed “Fatty” and “Slim.” “Slim,” characterized by its more delicate shape and more extreme cantilevers, was completed in New York. “Fatty,” the more massive of the two towers, was built at the National Training Center.

The skilled BAC craftworkers on the AAC team included, seated from left, Pat Rodgers of Local 4 NJ, Steve Shipley of Local 15 WV, Rick Pond of Local 3 NY, Henry Louie of Local 1 NY, and leader Bob Mion of Local 3 NY, along with, standing from left, Frank Koletar of Local 3 NY and David Bellucci of Local 1 MD/VA/DC.

Dubbeldam oversaw the project through visits and photographic documentation. But it was confidence in the skilled instructors and BAC craftworkers that made the difference. “I wish all my contractors could be as skilled,” she says. “Everyone was unbelievable, and it was the most supportive environment.”

Information sharing between the two IMI training centers included everything from dry stacking, rough shaping, anchoring, and methods for mechanical attachments, to labeling, packing and shipping the units for the final installation at the National Building Museum. Due to the limitations placed by other exhibits at the museum, the overall on-site construction time was a breakneck eight weeks.

For “Soundscapes,” this really meant seven weeks, with the first week devoted to modifying the exhibit hall foundation to take a load of nearly 20 tons. In the end, “Soundscapes” was completed before schedule, thanks in great part to the advanced planning of the entire BAC craftworker team.

No mention of “Soundscapes” can be made without including Thornton Tomasetti, the structural engineering firm that provided the research and design needed to assure its structural integrity. With cantilevers reaching six feet and centering points changing from course to course, attaining structural integrity was key to the project’s safe installation. Through the course of working on “Masonry Variations,” Thornton Tomasetti became more interested in the material and is now championing AAC as a choice for commercial and institutional projects.

Dubbeldam agrees. “It is very malleable, and acoustically really good. It’s a great material and I will definitely use it again.”
As with the companion installations in “Masonry Variations,” the success of the AAC project came from design and craftworker expertise. Taking an uncharted step into the future takes confidence on the part of each individual; taking the same step as a team also takes trust.

Looking back on the experience, Mion recalls: “I didn’t think it would be anything too big. We tinker around with the material and push it to the limit all the time. I didn’t feel that the architects would do anything more extreme with the material than we’ve already done…until I met the four architects. They had extremist ideas paired with craft people who, on the job and in spare time, have pushed these materials to limits. It was a match!”