The recent increase in the number of irregularly shaped tall building has caused a continuous increase in the formwork costs. To reduce the cost of forms, modular forms are widely used since they are cheap and reusable. However, they cannot be applied around columns which are irregularly arranged. This study introduces a formwork layout model using a genetic algorithm to reduce formwork material costs. The proposed model seeks an optimum formwork layout to maximize the proportion of modular forms by arranging 12 types of modular forms with the columns, for which the positions and sizes of are changeable. From a casestudy, the model showed a decrease in the ratio of non modular forms covering the area by about 11.9%, and the rental cost of forms can be reduced by 10.4% compared to the previous heuristic method. The model can be used in the structural planning stage by a structural engineer to reduce the cost of formwork, and increase the efficiency of the column layout.