1. Before construction, check the cracking, hollowing, flowing, edge warping, cracking, breaking, opening and damage of the original waterproof layer plane and facade, and check the leakage of cornices, gutters, parapets, ridges, water outlets, deformation joints, internal and external corners (corners), pipes protruding from the roof and other waterproof structures, and determine the removal sequence. 2. Remove the original waterproof layer and leveling layer a)