the facade curvature lines formed along the cluster of the curved panels thereby distorting the overall beauty of free-form buildings. Ensuring the as-built quality of the curved facade while meeting the free-form design intent is the responsibility of contractors [7]. To meet the quality requirements, the contractors should understand the distinctive limits of the panel materials used, e.g., plastic, glass, metal, and glass-fiber-reinforced concrete (GFRC), and appropriate fabrication methods to the materials.  
Two markets for free-form buildings exist in the construction industry. The first is for the contractors who can accommodate the mass production of the various shapes of free-form panels with cutting-edge computerized numerical control (CNC) based shaping technologies [8]. Projects under this category have been generally very big and capital-intensive, have involved diverse panel materials, and have required technical capacity for innovation imposing objectionable cost burden on the projects. The projects, therefore, have been occupied by renowned international construction firms which are competent enough to utilize the technologies and successfully handle the capital burdens [9]. Small/mid-size firms are rarely able to compete in the market to receive an order for construction. Examples of the projects under this category include the Walt Disney Concert Hall in USA, the Mercedes-Benz Museum in Germany, the Experience Music Project in USA, the Dongdaemoon Design Park in Korea, the Chanel Mobile Art Pavilion in France, the Guggenheim Museum in Spain, the Louis Vuitton Foundation for Creation in France, and so on [7].  
The second is to deliver small amounts of free-form panels to a project or to build a small size free-form building as a whole [9]. The contractors who belong to this category in general are small/mid-scale construction businesses in a regional market and mostly utilize traditional forming methods such as roller bending, press bending, and stretch bending, or mold-based forming techniques. While the conventional techniques are much cheaper and easier to approach than the cutting edge forming technologies to manufacture the free-form panels, it is obviously understandable that using those techniques can cause bigger as-built quality discrepancy than the cutting edge methodologies since the techniques depend greatly on the craftsmanship of free-form panel fabricators [6].  
According to previous research, among the three types of the curved panels, the double-curved panel is very difficult to form, showing bigger quality discrepancy than the other two panel types, which makes free-form projects overall very complex, often harming their geometrical beauty [10]. While comprehensive research is necessary for supporting small/mid-scale contractors to understand the methods of measuring as-built quality of the curved panel, the behavior of each panel type, the limit of the panel materials, and the proper production methods for the materials, thereby enhancing their project quality management capacity, most of the research in the area of free-form buildings has focused on mass and rapid panel production with cutting edge CNC-based technologies and the geometric design of the curved facade with meagre insight into small free-form buildings [11].  
The main objective of this study is to identify empirical lessons learned for the small/mid-scale contractors with which they can enhance capacity of managing the as-built quality of the curved free-form panels. To meet the research objective, the study performed a case study of a small free-form building and the mock-up tests of curved panels. Among diverse materials, the study focused on aluminum and GFRC panels. These two materials have been the most widely used as free-form panels.