Answer:
Based on my years of experience, when a new construction site is commissioned to install roofing and the central courtyard’s waterproofing, the materials are specified to be of the same brand and the contractor is the same company; the construction workers are the same batch of workers. However, after the completion of the construction and handover of the building, the probability of the central courtyard leaking is far higher than the probability of the roof leaking; especially in open spaces, the water drips from the central courtyard onto the ground floor of a high-end car’s paintwork; even after washing it, it cannot be removed; it is truly unbearable. The reason for this is as follows:
(1) The weight of the covering layer on the general courtyard waterproofing layer is much higher than the weight of the covering layer above the roof waterproofing layer.
(2) The movement rate of the atrium floor structure is much higher than that of the roof floor; in particular, the atrium structure itself not only has to withstand the weight of the A-building, but also has to account for the uneven subsidence of the B, C, D, and E-buildings, resulting in tensile forces on the atrium floor structure, so the probability of its floor cracking is much higher than that of the roof floor.
Because the conditions for waterproofing the courtyard and the roof are different from the “external forces,” the materials themselves and the construction quality must be even more rigorous. If general architectural designers, builders, and construction companies do not have these concepts, they often “apply the same conditions” to the bidding for the waterproofing of the roof, terrace, courtyard, and balcony, which will lead to this puzzling result.