Answer:
(i) The terraces and flat roofs on the deck are built with lightweight concrete 7 or 15 centimeters thick on steel-reinforced panels; most of the retaining walls are also made of PC panels or cement boards; due to the structural design requirements for seismic resistance, wind resistance, and light weight, they have a higher frequency of movement and insufficient stability. They are prone to cracking, and there are many joint areas and construction seams. Even a slight carelessness in waterproofing can easily lead to water leakage; once it happens, it is very difficult to repair it locally; a complete renovation is necessary.
(2) The new waterproofing work should pay attention to the following points:
(1) Before applying the waterproof material, any cracks larger than 0.3 mm in size on the substrate must be first treated (it is best to use an insulating method for large cracks).
(2) The construction seams around the drainage pipes and at all corners must be reinforced first, followed by applying reinforcement material of at least 15 centimeters above the surface.
(3) Before applying the waterproof material, the surface should be compacted with 2–3 mm of no-gap rubberized asphalt. Then, a modified asphalt waterproof felt with better elasticity should be applied. The vertical end sections must be secured with metal staples, and the seams should be sealed with sealant.
(4) For surfaces that are waterproof, if PU or acrylic rubber-type coating materials are used, the coating must be applied in multiple layers (no single-layer application is allowed).