Precast fabricators strive for business success in delivering products on time. To achieve this goal, fabricators start manufacturing once they receive specific design information. However, this strategy induces wasteful inventory. The objective of this study is to develop a Time Buffer Evaluation Model (TBEM) to promptly deliver products and maintain a smaller inventory. This model consists of two stages. The first, by using fuzzy logic, considers factors that influence construction duration. The second stage evaluates a time buffer by considering the tardiness penalty and crashing costs. In this study, one real case is tested to demonstrate the applicability of the proposed method. The application results show that the developed TBEM can reduce the level of finished goods inventory without changing production resources.