In all types of construction, the uncontrolled entry of water into the building walls can result in deterioration of elements within the wall system. Damages that can result from moisture in the walls include decay, corrosion, mold growth, poor indoor air quality, and decreased effectiveness of insulating components. Proper integration of a
moisture barrier with other components and proper water management techniques will effectively stop water penetration.
A moisture barrier has an important role to play in a wall system. Given that buildings are generally constructed tighter today than they were fifty years ago, the importance of a moisture barrier increases substantially, since water in walls may not readily dry.
A moisture barrier protects against condensation formation within the walls. In addition, use of a moisture barrier also protects the building sheathing materials like plywood, OSB, gypsum and CMU from molds, moisture and mildew.
An important advantage of a breathable moisture barrier in the wall is that it can help eliminate one of the major forces that cause water to get into walls: pressure difference. A moisture barrier, in combination with venting and compartmenting, enables the pressure behind the cladding material to equalize with the pressure outside, and prevent rainwater penetration caused by pressure differentials.
Various types of moisture barriers are available in the market today. In residential construction, polyethylene plastic is the most common moisture barrier. However, these types of moisture barriers, if not installed correctly, can leak, rip, or pull away from the sheathing, thus losing their effectiveness. Fluid applied moisture barriers are becoming common in commercial construction. They are essentially painted on to the substrate, (wood, gypsum sheathing, CMU or masonry) virtually eliminating the risks of tears or rips in the moisture barrier.
One of the most important things to keep in mind while installing a moisture barrier is that it should be continuous. There should be tight sealing of each component to the one next to it, as in wall-to-wall, wall to ceiling, etc.
The use of a moisture barrier is important in any climate. It protects the components of the wall system from damage caused by trapped moisture thus providing a more durable, sustainable wall system.
