After only a few years of intensive research all over the world, 3D printing of buildings has become possible. However, existing design codes do not cover all the special technical features of the new construction method. Therefore, it is necessary to develop supplementary and adapted test procedures as well as design standards. In addition, a building permit (approval for individual case) must be issued. In this paper, we describe a concept to obtain an approval for individual case for the construction of the first 3D-printed detached house in Beckum, Germany, following existing standards for concrete and masonry construction. To choose the right test methods, one must know the design of the building, the additive manufacturing technique, the material, and the production environment. In the presented case, the house was completely built on the building site. The design of the house used 3D-printed parts for inner and outer walls for load-bearing and non-load-bearing elements. For this purpose, material properties such as setting, direction-dependent strength, and durability were tested. However, due to the scope of the paper, only flexural strength measurements are addressed here. All investigations focused on the formation of cold joints due to breaks in the construction process and the environmental impact. However, due to scale effects, testing of large-scale elements was necessary. In particular, larger wall elements showed decreased flexural strength compared to smaller specimens (prisms). Therefore, we present a concept for testing the load-bearing performance of wall elements and their resistance to the pressure of fresh concrete. All tests were successfully applied, characteristic design values were provided, the approval for individual case was granted, and the construction process began.