Answer:
(i) If PU construction is used, the waterproof function of the RC wall remains intact; the only drawback is that the surface cannot be painted or primed; however, in the case of brick construction, since it is very difficult to completely dry, water vapor can damage the PU curing structure, resulting in partial hydrolysis—the so-called rebound phenomenon (the situation with carbon fiber PU is more severe; with petroleum-based PU, it is more favorable).
(2) For bathrooms that truly require polyamide (PU) waterproofing, it is recommended to apply it only to the floor (maximum height of 5–10 cm). For the wall sections, it is still recommended to use water-based and solid-state waterproofing materials.
(3) Advantages: Since it is a water-soluble material, it has the advantages of good adhesion, resistance to the effects of both dry and wet conditions on the site, and quick construction.
Disadvantages:
(1) The waterproof material can be easily added with water or emulsified petroleum to affect its waterproof function.
(2) Under conditions of prolonged standing water, there is a risk of subsequent complications such as hydrolysis and skin erosion.
(3) The construction thickness is not easy to control.
(4) Compared to the subsequent coating for construction work, the strength is lower.