The outer surface of an irregular structure contains panels with two-directional curvature called NURBS. To construct these forms of exterior materials, complex geometric surface should be divided into forms and sizes that can be manufactured and constructed. Because the bigger the curvatures of these divided exterior panel, the more expensive the construction costs, these complex two-directional curvatures should go through optimal process of reinterpretation to minimize the curved surfaces with complex two-directional curvatures. Yet, to gain higher ground in technological competition in the field of irregular structure construction, companies do not share know-how that they obtained. Accordingly, small construction and design companies have trouble calculating even rough estimate and cannot adjust expected construction cost based on comparison of design alternatives. Given this situation, this study conducted the research that can support decision-making in the design stage of the construction and provide basic material for optimal range to reduce manufacturing cost by the minimizing the distorted plane of the irregular structure.