How to compensate for the property losses caused by external wall leakage and interior decoration?

During the warranty period, the blank room leaked water due to the damage of waterproof layer (1). If the customer personally confirms the 24-hour closed water experiment when closing the house, the customer is responsible; (2) If the customer does not personally confirm, the developer only has the certificate of completion acceptance, which can prove that man-made damage is the customer's responsibility; If the responsibility is not clear, both parties shall settle it through consultation; If negotiation fails, the third party shall apply for appraisal, and the expenses after appraisal shall be borne by the responsible party;