The optimization of costs and time is very important to construction activities. It is used as a planning to get the best cost and time so that the optimal benefit of the project. To achieve the advantage then do steps to reach cost and time optimization such as making network project, find the critical path, calculate the duration of the project and know the amount of resources. There are several ways of achieving cost optimization in project activities, such as the addition of working hours (overtime), the addition of labor and the addition of heavy equipment (for projects that use heavy equipment). From each of these alternatives will get the results in the form of an acceleration of the same duration but the resulting costs will be different. On the research of development projects in the form of building method using time-cost trade off with two alternative calculation with addition of working hours (overtime) and additions to the labor. From the analysis conducted most optimal results are obtained with the addition of a workforce equivalent to 3 hours of overtime that is Rp.2.425.905.797,13 of the normal cost of Rp. Rp.2.721.121.828,85 with a duration of the acceleration becomes 62,93 days from a normal duration is 147 days.