Water-resistant barrier requirements (i.e., code and industry guidelines) within portland cement-based plaster (stucco) wall cladding systems have changed over the past decade. Various types of water-resistant barriers have been developed, and different configurations for their use within stucco wall cladding systems have been implemented successfully. However, improper use or lack of a proper water-resistant barrier can lead to deterioration or corrosion of exterior wall components, including sheathing, framing, and insulation, and can eventually result in water leakage into interior spaces.

This paper will review the changes in water-resistant barrier requirements for exterior stucco wall cladding systems. It discusses the mechanisms for failure and water leakage paths through stucco cladding systems and water-resistance barriers, presented through various case studies. Laboratory testing of various types of water-resistant barrier materials will also be performed. Comparisons of the results are explored along with examples of actual in-service installations.