In masonry cavity walls—a design that has been in use for more than a century—the cavity provides a path for drainage and ventilation and acts as a capillary break. However, adhered masonry veneers like stucco and stone have been installed for hundreds of years without drainage or ventilation. So why do we need to add drainage and ventilation planes to adhered masonry walls now? The short answer is Standard 90.1, Energy Standard for Buildings Except Low-rise Residential Buildings, from the American Society of Heating, Refrigerating, and Air-conditioning Engineers.
ASHRAE is an international organization that sets energy-use standards for commercial buildings. It standards are frequently used as the basis for building codes throughout the United States and Canada. Increasingly strict energy codes are derived from ASHRAE 90.1 as well as recent changes in building materials, which has made drainage and ventilation for adhered masonry walls just as important as they are for masonry cavity walls. Here are the top seven reasons to specify and install drainage planes in adhered masonry wall systems.