There are several issues related to the implementation of new Industrialised Building System (IBS) technology in Malaysia which some of them are the awareness among industry players, and lack of development on the new technology in the industry. The main constraint that has always been discussed by the IBS players is time and cost. To have more reliable product or technology in terms of cost and time, it is important to craft and develop new idea as well as technology in our own country. The objective of this study was to highlight the cost comparison between cast in-situ concrete slab and hollow core slab (lightweight) which it can be a starting point for future research on the development of new lightweight IBS technology in Malaysia to get the most reliable cost with latest technology by using local resources. Informations on costs and work durations are collected and analysed between two floors using two different construction methods (hollow core slab and conventional concrete slab). Hollow core slab (lightweight IBS) has similar or less cost with shorter construction period (30% shorter) for the project.