To pursue reasonable systems which avoid lacks of essential performance of construction, we organize the structure of building performance with two points of view: the subjects who require performance, and imperfect information. One subject, client can order his requirements to builders, but the other, the public can't. Hence, the clients and the builders have less incentive to achieve requirements of the public. In turn, information of building performance is imperfect, so that the clients or the public cannot discover defects. The degrees of imperfect information are two: asymmetric information between client and builder, and unforeseeable performance of all.