StuccoMetrics: Performance Testing and Evaluation of Drainage Screed Flashings and Drainage Subassemblies Used in Stucco Drainage Wall Systems

December 24, 2015
Publication: ASTM International, Advances in Gypsum Technologies and Building Systems

Building codes require a concealed water-resistive barrier (WRB) with a means of drainage (drainage subassembly) at the base of an exterior Portland cement-based plaster (stucco) drainage wall. Although not mandated, similar drainage screed flashings and subassemblies are used at window and door heads and occasionally at soffit corners to facilitate drainage at locations susceptible to water intrusion and damage. Drainage screed flashings are critical components of drainage subassemblies, but little is known about the actual performance of these drainage screed flashings and drainage subassemblies. Therefore, we tested and evaluated 20 specimens consisting of five drainage screed flashings and four different subassemblies. This paper describes the development of drainage screed flashings, outlines relevant building code requirements of these components, highlights the importance of drainage screed flashing and drainage assemblies, and examines some problematic as-build conditions when drainage features are not present. We also present our observations, findings, and conclusions from our qualitative testing of the 20 test specimens.

Keywords: Drainage Plaster Stucco