This study aims to analyze the application of Precast half-slab formwork with conventional formwork in terms of cost and time. The use of precast concrete is based on advantages in terms of economy, efficiency, speed in implementation, and energy consumption which has an impact on the environment. This office construction project was carried out in the Graha Family area in Surabaya. This project uses the half slab precast method, where half of the plate (precast) is precast with a thickness of 7 cm, and the other half is cast on site (topping). In this final project research, an analysis and comparison of several methods of floor slab work is carried out so that it can be seen which method is considered more profitable. Analysis of conventional half slab and precast methods focuses on calculating direct costs in terms of materials, tools, and workers' wages as well as calculating the time needed to complete the work.