The most frequently asked question from our clients is; 'what can be done to stop water leaking through the curtain wall'. Simply speaking, there are three necessary design elements that must be incorporated in any reliable curtain wall system, namely: Collection: The design must direct any infiltrating water to predetermined locations in a controlled manner, without allowing any uncontrolled migration. Drainage: The curtain wall system must provide sufficient means for the water to escape. Back-up Drainage: The curtain wall system must provide a second line of defense, so that no single waterproofing detail is critical to the overall design integrity. Even if all of the above concerns are adequately met, leakage may occur if the design fails to consider that there are five different 'forces' which compel water to move from the outside of a building to the inside, namely: Gravity: The most common leaks result from simple openings in the curtain wall whereby the water just drips in. Capillary: The inclination for water to filter through porous materials or hairline joints and cracks. Surface Tension: Water will tend to follow a surface, even turning 90? around corners, such as soffits. Pressure Differential: If there is a net pressure difference between the inside and outside of a building, water that may be present on the outside surface will readily pass through small defects in the waterproofing system. Kinetic: Wind driven rain has the velocity and momentum to carry water into areas, which may not have been considered as wettable in the design, such a counterflashings. Another associated water leakage problem is water that has penetrated from the exterior but does not leak into the interior. It may be trapped within the curtain wall, whereby it promotes corrosion of the system and condensation to appear on the interior glass lites.