1. Using improper waterproof layer material. For example, material indicators do not meet the requirements, construction thickness is not enough, improper process,etc. Improper mixing use of more than two kinds of waterproof materials may enflunce the waterproof effect.

2. The weak part of waterproof layer is cut off by the groundwater. The waterproof layer of basement floor corner line may be easily crack. If structure settlement happens, this parts are easy to crack. The construction of basement floor flexible waterproof layer adopts inner paste and outside protection method, which cannot get the waterproof layer and structure layer bonding tightly, when the deformation happens, the flexible waterproof layer is easily take off.

3. Waterproof layer is perforation damaged by concrete defects. This is due to the uneven subsidence and cracking bring the damage of flexible waterproof layer; If there's out hole in the concrete, people don't know at this time also can't repair concrete. Waterproof layer attaching back fails, and small part of waterproof layer is punctured by the effect of water pressure.

4. Shield damage or deformation of flexible waterproof wall with sleeve facade outside paste outside protection method may make partical damage of the waterproof layer. The flexible waterproof layer of basement wall usually adopts the concrete structure then use out paste and out protection method for construction. it has the advantage that the flexible waterproof layer can be well combined with structural concrete, but the current method mostly maybe build a brick protective layer outside of the waterproof layer. When the apparent sink or during the backfill, the protective brick layer maybe break or deform or vibrate and damage the waterproof layer.