<p>Case study on an office building is conducted using a novel performance-based method for verifying compatibility of fire spread prevention performance of a building with that required by the building standard law. In order to relax the restriction on the fire-resistive performance of the inner wall and floor to be equivalent to the quasi-fire-resistive construction of 45 minutes, it is necessary not only to improve the fire-resistive performance of the external wall and window, but also to subdivide the inner space into several fire compartments.</p>