The reasons for water leakage in the underground exterior wall are complex, as they are influenced by both the construction quality and external factors surrounding the building. Different causes contribute to the various leakage issues mentioned above:

External factors include situations where surface water from the building's exterior (such as rainwater or domestic water) fails to be promptly drained away, seeping into the ground or leaking through underground pipelines, leading to the underground exterior walls of the building being exposed to water for an extended period, resulting in water leakage.

2. Internally (regarding the project itself):

Water leakage at the base of the wall, primarily caused by inadequate cleaning during the plastering of the interior and exterior walls, resulting in the waterproof mortar not reaching the bottom or the plaster at the base not being dense enough. There are gaps at the junction of the interior wall plaster and the ground surface layer, leading to water leakage, especially when the elevation of the wall root is close to the indoor ground level of the basement, making this situation more likely to occur.

(2) Water leakage at expansion joints is primarily due to inadequate waterproofing measures at the joints, allowing groundwater from outside to seep into the expansion joints and then infiltrate the basement through the walls on both sides of the joints.

(3) Water leakage through exterior wall pipes is caused by the pipe holes not being sealed properly, with groundwater seeping into the interior along the outer surface of the pipe walls during heavy rain in summer or when there are pipe leaks.

(4) Water leakage at the exterior wall's drainage area is due to the waterproofing mortar on the outer side of the wall being lower than or equal to the drainage level, and the joint area between the outdoor skirting and the drainage often fails to bond properly, sometimes not bonding at all. When the drainage cracks or the gap between the drainage and the plinth is not sealed with sealant, heavy rain can lead to water seepage into the basement.

(5) Some wall leaks are due to insufficient mortar during the construction of the walls, creating gaps between the bricks, through which rainwater seeps in.