Moisture Intrusion in Buildings

Moisture is commonly regarded as the single greatest threat to durability and long-term performance of buildings. Excessive building exposure to moisture is a common cause of significant damage to building components and materials and unhealthy indoor environments. Serious adverse effects can result from moisture problems in buildings. Successful management of moisture in its various forms is essential for buildings to be durable, safe, and energy efficient.

Moisture in buildings is a major contributor to mold growth, unhealthy buildings, and poor indoor air quality. Wet building walls and rainwater leaks are major causes of water infiltration but so is excessive indoor moisture generation. Preventive and remedial measures include rainwater tight detail design; prevention of uncontrolled air movement; reduction of indoor air moisture content; reduction of water vapor diffusion into walls and roofs; selection of building materials with appropriate water transmission characteristics; and proper field workmanship quality control.

Moisture causes problems for building owners, maintenance personnel and occupants. Many common moisture problems can be traced to poor building design, construction or maintenance. The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) notes that, more often than not, many problems are caused by decisions made by members of any of a number of different professions made pre or post construction prior to occupancy. Such problems can be avoided with techniques that are based on a solid understanding of how water behaves in buildings.

Common building envelope failures include improperly installed windows, compromised window and door seals, stucco to concrete connection failures, grade issues, missing vapor or compromised vapor barriers and roof leaks. Common moisture vapor related issues include incorrect mechanical system design, incorrect outdoor make up air introduction and improper exhaust fan operation.