The 2021 IBC has now been published, and with it came some significant changes/improvements for stucco assemblies over wood-based sheathing. As a builder, designer, architect or even inspector, it will be important to know what those changes are. This article will address the changes and some useful improvements made to the Portland cement stucco water-resistive barrier provisions per the 2021 IBC.
Portland cement (conventional) stucco, anchored masonry, brick veneers, adhered masonry veneers, and anchored brick masonry can absorb and store significant amounts of rainwater. Eventually, solar-driven drying occurs after the rain and inward vapor drives can exceed the amount of outward vapor drives. This will typically result in elevated exterior sheathing moisture contents. Needless to say, excessive moisture content in the exterior wall can lead to a host of other issues. For this reason, some enhanced practices are essential to protect the moisture-sensitive portions of the wall assembly from getting damp from inward vapor drives.