Causes of water leakage in U-shaped glass curtain wall

1. Material-related causes

Joints are the main locations where gaps occur in U-shaped glass curtain walls. Examination of projects in China shows that, apart from opening sashes, the first line of waterproofing at most joints relies on construction sealants. Water can enter if the sealant cracks or if tiny gaps develop, even when they are invisible to the naked eye.

Water leakage can result when weather-resistant silicone sealant is unsuitable, does not meet the specified technical requirements, or is replaced with structural adhesive. Bubbling and cracking in the sealant joints are major causes of leakage.

2. Design reasons

External loads on the U-shaped glass curtain wall are ultimately carried by the aluminum profiles. If the mullions or transoms are insufficiently strong, the curtain wall may deform more than expected. This can overstretch the sealant or create gaps too large for it to seal effectively. Opening sashes that do not close tightly can also cause water ingress. Improper structural design is another major cause of gaps. For example, failed waterproof seals or too few sealing layers around opening windows, where the general standard is 2-3 seals 1, can allow rainwater running down the curtain wall to enter the windows directly.

3. Interface reasons

Some aluminum profiles have surface finishes that do not meet national standards. Poor coating adhesion or an oxide film that is too thin or too thick can cause sealant adhesion failure and cracking.

4. Construction reasons

Installing U-shaped glass curtain walls requires precision. Incorrect frame installation, poor surface preparation, or inappropriate sealant width and thickness can create hidden leakage risks. Connections to the main building are especially vulnerable when curtain-wall and general contractors work separately without sufficient coordination. Inadequate detailing or poor workmanship can leave paths for water ingress. For example, poor coordination at the junction between the curtain-wall head and parapet can result in incomplete or missing seals.