Water leaks around windows and doors cause significant damage to homes and create an environment in which mold can grow. A water leak can go undetected for years requiring costly mold remediation and repair. Media reports about water leak problems and a thriving water damage repair industry are clear signs that water control is a common problem. The time to address water control is during construction. A little time, effort, and money spent on proper flashing and other water control measures can prevent major problems later. Note the use of the term water control rather than the use of a term like leak prevention. The reason is that a strategy based on preventing water leaks around windows and doors will probably fail. Materials and installation are rarely perfect and water is relentless; it will find any opening. The more realistic strategy is to assume imperfect materials and installation, then design a system to drain water out of the structure before it does damage. If proper water control measures are so important and so rare, why don't all windows and doors leak? Many do leak, but the cycle of wetting and drying is such that there is no significant damage. Regular maintenance of caulk can control many leaks. Other leaks and damage are controlled by nothing more than luck. water leak detection Some windows and doors are more vulnerable to leaking. Among the most vulnerable are those facing prevailing storm winds (usually east or west), those facing long open areas without trees or buildings to divert the wind, those subjected to water from the roof, and those on the second story or above. You should not rely on lack of vulnerability or on luck to control water leaks. The key to water control is to install a drainage plane. A drainage plane is a system of water shedding materials, such as flashing and water-resistant paper, arranged in a manner that directs water down the plane and away from the structure. Roof coverings, such as shingles, are the most common example of a drainage plane. Because water flows down hill, each layer of roofing material overlaps the layer below by enough to restrict wind-driven water from flowing up and under the drainage plane. A wall drainage plane is similar with each layer of water-resistant material and flashing overlapping the layer below. Properly installed, this system will control almost all water intrusion into the home and will operate without degrading and without the need for most maintenance over the life of the structure. Why don't contractors install a functional drainage plane? There are at least three reasons. One, water control costs more and contractors are often reluctant to spend money on systems that are not required. Two, there is no demand from homebuyers for this important feature. Three, building codes require flashing, but they are not specific about how to install flashing.