The whole thing about precast concrete is that it is “pre” cast, meaning the concrete is poured and solidified elsewhere, in a highly controlled environment (that makes it easier to achieve smooth, high-quality pieces of concrete in unusual geometries – what we were going for). The downside of precast is that you then must transport the concrete pieces to your site and install them there. Transporting a large precast block is logistically challenging and expensive, installing a large precast block is as well.

This meant that we needed to break down the precast elements into segments, or smaller precast pieces. This posed another financial challenge, because the more unique pieces we had, the more expensive the design was. Each unique precast piece needed a unique mold to form it. The more molds we needed, the more expensive our project was. If we could find ways to repeat precast pieces within the design, we could use the same mold more than once and the project would be less expensive.

However, the fluid SD design was highly irregular and the changing topography on site meant that even if in plan view the shapes were the same, they had different heights or were interfacing different materials that made it hard to repeat the same piece. This taught me that designing with modular elements from the beginning would have been a great way of saving money, time, and effort further along in the design process. We tried to redesign our site to make it much more modular, but that posed a lot of new layout changes and challenges that would have a ripple effect throughout the design work we had already done. Besides, the client loved the way the SD layout looked and was willing to spend more on unique precast pieces. We decided to find another way to make the project cheaper.

Originally, we had envisioned the precast pieces as solid precast blocks, but during the value engineering process, we found that we could use precast concrete caps instead. Underneath the precast concrete caps, we’d have cast-in-place (CIP) concrete foundations which were a lot cheaper. We moved forward with this solution. To the left you can see the evolution of the precast concrete details before value engineering (as solid blocks) and into caps atop CIP concrete in the final version. Below you can also see the unique precast wall pieces that were dimensioned in plan view as part of the final drawing set.