Cement Plaster Metrics: Quantifying Stucco Shrinkage and Other Movements/Consensus Cracking Accepting Criteria for Evaluating Stucco

November 29, 2010
Publication: RCI Symposium On Building Envelope Technology
Author(s): Bowlsby, Jeffrey A.

Abstract: Building design and construction professionals and cement plaster product manufacturers acknowledge that Portland cement plaster (stucco) shrinks as it cures and moves with changing environmental conditions while in service, but by how much? Published information quantifying the magnitude of shrinkage and other movements is scarce but does exist for stucco installations as early as the 1940s. Detailed information from several documented stucco installations and manufactured products with published shrinkage data will be presented, compared, and discussed. Cement plaster cracking is inherently related to shrinkage and other movements. Stucco crack acceptability criteria, which vary widely, are published by a multitude of industry sources, with no objective industry consensus. Acceptability criteria from known published sources are tabulated, presented, and compared to identify common factors and anomalies. The intent is to establish objective, unbiased criteria for use by industry practitioners.|This information has been extensively researched and observed over many years. It should prove useful to interested parties in effectively understanding and accommodating cement plaster shrinkage and movement characteristics during the design and construction process and serve as a resource when evaluating cracks in stucco installations.

Keywords: Cracking Stucco