When selecting between lightweight steel joist floor systems and heavier composite or non-composite systems using rolled steel beams, two issues are generally considered to be in competition. These two considerations are cost and vibration serviceability. In general, it is thought that even though the joist floor is more prone to disturbing vibration levels, it is sometimes a better choice based on economy. This paper explores a whole building cost approach to assessing the economy of the lighter joist system relative to its rolled beam competitor. It is illustrated that other building systems, such as fire protection, are affected by the selection of the floor system, thus affecting total building cost. The end result is a closing of the cost gap between heavier rolled beam floors and lighter joist floors. Copyright ASCE 2006.