Cost has been traditionally known as a key factor that needs to be considered in the decision making process. Recent awareness in environmental problems has highlighted the need for considering environmental impacts into the process of making choices. However, far too little attention has been paid to reflect the environmental impact and the building cost into the decision making process. As such, this study proposed a method that integrates and considers the environmental cost and building cost in the structural design process. This method takes into account the cost associated with building materials, construction methods and amount of embodied carbon emission during the life cycle of buildings. The current study analysed the effects of two construction systems (Flat slab and waffle slab) and two structural materials (Normal concrete and Ultra-lightweight concrete) on overall costs of a typical high rise concrete structure (15-story office building) in Australia (NS11401.1 2014). The results show that the office building designed with lightweight construction method (waffle slab) and normal concrete (Normal weight) has a lower life cycle cost (50 year lifespan) in comparison with the other design alternatives. It was found that an appropriate selecting of construction forms and type of concrete can save up to 7% of the cost of material consumption, 5% of the total energy consumption expense, and 5% of the CO2-e emissions of the building across all five major cities. This study demonstrates a method to quantify the potential impact of Ultra-lightweight concrete has on the life cycle cost and carbon emissions of commercial buildings. The proposed methodology to assess life cycle cost and environmental impact can be used as a supporting tool in selection of efficient construction methods and structural materials over the lifetime of building.