Kotaro Ide, of Artechnic created a residential building “SHELL” using ArchiCAD. Located in one of Japan’s most prestigious resort towns the villa was designed to maintain harmony with the environment. The building boasts a bold design springing from a concrete tube as a base form. Ide focused on creating his design in a 3D model, following client requests, while maintaining durability.
In creating a curved surface with “constructability” in mind, Ide also needed to satisfy general requirements for the villa. Chief among the requirements for the villa were the need to build a residence that could withstand harsh Karusizawa winters and hot, humid summers. “Wooden houses don’t last so we decided on an image of using a concrete shell, which ‘floats’ above the ground,” explains Ide. “I wanted to form the concrete without any joints in order for the building to stand up to the harsh environment. We modified the shape to a tube, and used a method of forming the bottom and the sides using formwork casting; for the roof, only the bottom surface would have formwork, and concrete would be poured into it using a plastering method,” he explained.
The concrete is 330mm thick on the top and bottom, while the sides are 730mm thick, giving the form successive changes. The final design depended heavily on mechanical basics. A cross-section of the ArchiCAD model was created and used for plastering work. The inside surface of the concrete was sprayed with 60mm thick, rigid urethane for insulation; an additional 10mm of hygroscopic finishing was sprayed on top.
A level of perfection only 3D can achieve
Inside SHELL, the floorboards are laid about 1.4m above the ground level, and furniture, windows and doors were placed on top. Curved surfaces do not waste the usable space in this villa. In fact ArchiCAD allowed for the planning of efficient placement of sofas and a kitchen in this project. “ArchiCAD was really useful when testing the placements and shapes of furniture and equipment near the curved surface. On 2D drawings it is hard to generate the intersection point coordinate, so you could only review that about 2 to 3 times within the limited time of design, whereas with ArchiCAD it is possible to simulate about 20 times repeatedly. As a result, the design perfection level became very high,” explained Ide.
The interior elevation drawing for openings were also generated from ArchiCAD model data. The construction involved placing openings along the elliptical surfaces of the tube. The designer was pleased that the maximum precision error in calculating the concrete casting construction was about 3mm. That accuracy provided installation of windows designed with CAD measurements to be installed without problems. Pipes and other ventilation equipment were placed mainly under the floor – so as to minimize effort and eliminate the process of draining the water during winter absences.