Flat 40 is a minimalist house located in Imabari City, Japan, designed by K2 Design. A seven-story apartment building towers on the south side of the property. The concern was how to block the line of vision from the apartment building and maintain privacy, while ensuring ample light and ventilation. In order to meet these requirements we designed a 40 meter concrete screen wall along the south side of the residence. Precise calculations were done for its size and structure.