How to get to Thornton Tomasetti

3D printing processes in building construction are not yet anchored in building regulations. This brings with it hurdles in the approval process. A US company that offers 3D printers for the construction industry is now looking to set a precedent to convince the authorities.

Building regulations are usually the result of an eventful history - a number of regulations that are taken for granted today were only initiated after serious tragedies. For example, the Hamburg fire, which devastated large parts of the old town in 1842, led to the enactment of fire protection regulations by the building authorities and (in view of COVID-19 again highly topical) laws to ensure public safety in densely populated urban areas. But with all the rules and guidelines, the building regulations landscape is more fragmented than ever. A model building code presented in 1960 by the German building ministers' conference ARGEBAU was initially largely adopted by the individual federal states, but has since been individually adapted, supplemented and revised beyond recognition. And at the international level, too, there is a lively confusion of various regulations.

Within this confusing environment, another challenge now arises: the evaluation of new technologies in the context of the construction industry. 3D printing in particular promises to revolutionize the sector and make construction processes faster, more affordable, safer and more sustainable - provided that building owners can appease the building authorities and answer their most pressing question: Are buildings made from 3D printers really safe?

Anna Cheniuntai, founder and CEO of the Boston-based company Apis Cor, which offers specialized 3D printers for the construction industry, also knows these hurdles: “3D printing is a really innovative and revolutionary technology. The construction industry, on the other hand, is very conservative, which makes the use of 3D printing technology difficult in practice. Our greatest challenge at the moment is to establish norms and standards that make it easier for building supervisory authorities to draw up appropriate certifications and issue building permits. "

Together with Thornton Tomasetti, a company specializing in building construction, Apis Cor is currently developing an industry standard for 3D-printed wall structures. This should - so the hope of the two participants in the residency program at the Autodesk Technology Center in Boston - represent a first step towards future-oriented building regulations.

Authorities need precedent

Since its inception, Apis Cor has demonstrated the benefits of 3D printing in a handful of projects. With the help of a mobile concrete printer, the company built what it claims to be the first house in the world to be printed “on site” in Stupino, Russia, in 2016. The approximately 37 square meter, circular building was erected in just 24 hours for just under 10,000 US dollars. If you consider that the aid organization Habitat for Humanity needs an average of 50,000 US dollars and eight months to build an almost 100 square meter apartment, Apis Cor's approach promises greater time and cost efficiency.

Apis Cor recorded another success in October 2019 with the order to contribute wall structures made using the 3D process for a two-story administration building in Dubai. With a height of 9.5 meters and a total area of ​​around 60 square meters, the largest building to date was created from the 3D printer.

Although the company had the proof of concept in its pocket, it did not have a sufficiently strong precedent - however, exactly such a precedent is needed to convince the responsible building authorities to give the green light for large-scale 3D printing projects, says Patrick Kenny, partner and engineer at Thornton Tomasetti.

“Construction and manufacturing are two different things,” says Kenny. “The current state of the construction industry does not allow any number of copies of the same building to be erected. In production, on the other hand, you can screw up the first ten attempts without major consequences and gradually optimize the process. Since every building is its own prototype, most decision-makers tend to approach it conservatively. "

This is exactly where building codes come into play. By defining generally applicable standards, building authorities bring uniformity to otherwise inconsistent building structures. On the basis of past construction projects, they develop patterns that will help reduce risk in the future. The problem with new technologies: There is a lack of appropriate patterns that could serve as a guide. This is exactly what Apis Cor would like to change.

In order to position 3D printing as a sensible alternative in the eyes of the building authorities, the team is concentrating exclusively on 3D printed wall structures. The design is based on traditional shell stones - including a cavity for attaching reinforcing bars. Although 3D printing enables radically new forms in theory, for the Apis Cor team, the search for similarities with traditional processes is crucial for legitimizing new construction methods.

The comparison with conventional masonry is intended to facilitate approval procedures

“The aim is to show the structural similarity of our results from the 3D printer with conventional masonry. We are convinced that this would simplify the approval process, as the building authorities would be able to orient themselves to the rules and building regulations of an established division, ”explains Cheniuntai. Meanwhile, the advantage for construction companies is that proven construction techniques - starting with the laying of foundations up to the construction of roofs - can be easily transferred to this new method.

Instead of using more unusual building materials such as carbon fiber or bioplastics, Cheniuntai and her colleagues consciously use well-known favorites such as concrete - with one crucial difference: Since conventional concrete is not suitable for 3D printing processes, the team combines the basic ingredients - water, sand and cement - with a secret building material that gives the material an optimal viscosity and curing time.

"We know that the first thing to do is to get as familiar as possible with the building materials commonly used in the industry," emphasizes Cheniuntai. "We can then dare to move on to new materials later."

Of course, 3D-printed structures that look like traditional masonry only make sense if they can keep up with their role model from a functional point of view. With the support of Briggs Engineering and Testing and the University of Connecticut, the Apis Cor team subjected its walls to the same tests certified by the international standardization organization ASTM International, which are also applied to scarf stones. This includes, for example, the evaluation of strength, resistance, bending resistance and degree of compression.

“The strength of a shell stone is determined by determining the load limit under high pressure. So we subjected a 3D module in the exact format of a shell stone to the same procedure, ”explains Kenny. Thornton Tomasetti's team is responsible for evaluating the tests and recording the results in the form of a document that can be easily shared with building authorities. "In this way we want to make it clear that this new type of building material meets all the requirements of the existing, very comparable building regulations in connection with shell stones," he explains.

As part of two planned demonstration projects, it is now important to put the empirical test results to the test of practice. The first project - a 3D printed two-story house in Jackson, Louisiana - is slated to be completed in just two weeks and cost half the price of a traditional house. The second, for which Apis Cor partnered with the Housing Trust Fund of Santa Barbara County, is to use 3D printing to create affordable housing in Santa Barbara, California. Both projects are expected to start in autumn 2020 and have to go through the usual approval process - the ideal opportunity to present the benefits and governance structures of 3D printing technology.

“We want to convince a certain number of people of our approach in a few places. Then we would have a precedent that shows that a building has been built like this before, ”says Kenny. While simplicity should be the focus of initial projects, the team plans to introduce additional prototypes with more unusual designs over time. Of course, these too will first have to win the favor of the building authorities.

Future vision: sooner or later, 3D printing processes will become an integral part of established concrete construction regulations

“At the moment, building regulations in connection with paving stones are the focus of our efforts. The relevant regulations are quite rigid and stuck, but on the other hand they are easy to understand and very precisely defined, ”says Kenny. “I am confident that 3D printing processes will sooner or later become an integral part of established concrete construction regulations. Because despite all the requirements in this area, there are no restrictions whatsoever with regard to the structural shape - these are ideal conditions for 3D-printed concrete structures. "

3D printing promises to transform the real estate industry from the ground up through the fast and affordable creation of housing. It may be a long way to get there, but for Cheniuntai and her team it is clear that it is worth doing: “There is still a lot to be done when it comes to affordable living space. We are convinced that we can really achieve something big in this regard - but of course we first have to get the necessary permits and approvals, ”the Apis Cor director sums up. "The biggest challenge will certainly be the scaling of the technology."