Buildings clad with multiple facade components perform well when they are properly designed and constructed. When water leakage does occur, typically it happens at the interface of the different components. The authors have performed numerous field investigations regarding water leakage of buildings and will discuss, through case studies, reasons for the leakage at the interface and examine how it could have been avoided. Additionally, design principles will be discussed regarding better water resistance performance of these interfaces. Problems with water leakage can be avoided if designers, manufacturers and installers perform a thorough study of each material and it's interface with adjacent materials. Through the cooperation of these parties in the development of a complete understanding of each component and its interface with the other components, proper design and detailing, pre-construction meetings with all parties, pre-construction mock-up testing, on-site field observation, and quality control testing, water tight buildings can be erected.