Stuccometrics: Stucco Jointing – The Why, When, Where and How

This presentation initially took place at the 2020 Convention.

Exterior stucco cladding can be categorized into one of two configuration types—either directly-applied to cementitious and masonry substrates (barrier walls), or applied over lathing that is mechanically fastened over a water-resistive barrier to steel- or wood-framed substrates (drainage walls). Both configurations often employ a range of stucco cladding jointing types serving different functional and aesthetic purposes. The objective facts of Why and When stucco jointing is needed or not needed, Where joints are needed, and How joints are designed and constructed are explored, including significant new information that promotes knowledge and understanding to improve the performance and quality of stucco claddings, which are often misunderstood.

This article is based on historical development, design, and installation requirements; building code and reference standard requirements; and the results of recent stucco jointing performance testing. Provided illustrations will depict stucco jointing construction detailing, lathing accessories, splicing, intersection and termination requirements, and plaster application methods used to configure stucco jointing. This presentation factually and objectively explains essential requirements and considerations for effective stucco jointing to assist stucco cladding designers and craftsmen. Jointing facilitates drainage, accommodating building substrate movement and cement plaster shrinkage movement, thus reducing cracking, while it terminates cement plaster panel areas and has decorative purposes.

Jeff Bowlsby, CCS, CCCA

Simpson Gumpertz & Heger, Inc. | San Francisco, CA

Jeff Bowlsby is an architect and stucco consultant with 35 years of construction industry experience. He leads the ASTM C1063 Installation of Lathing and Furring for Portland Cement-Based Plaster task group and founded and leads the ASTM C11 Stucco Work Group that develops all ASTM stucco-related industry standards. He has completed performance testing of stucco assemblies and components, published several stucco-related technical articles in national industry professional journals, is the author of the stucco information resource StuccoMetrics.com, and is a frequent industry presenter on stucco wall claddings. Bowlsby is skilled in building science issues and the integration of all building enclosure systems and components.