Evaluation of Three-Coat Stucco Installations on Commercial Buildings

Three-coat stucco (Portland cement plaster) has been successfully used as an exterior finish and weather barrier on residential structures for over a hundred years. Residential stucco is considered a highly durable material with typical lifespans in the range of 50 to 75 years. The authors have noted that in the last 20 years three-coat stucco has been increasingly used on commercial building, including mid-rise and high rise buildings. This trend may be related to the competitive aspects of stucco as an exterior finish as well as the reluctance of some architects to design with EIFS (synthetic stucco). However the performance of the stucco on commercial buildings has been, in the author's experience, rather mixed. The authors have investigated a number of commercial buildings where significant water intrusion problems have been related to the design and application of the stucco system. This paper presents a summary of problems we have observed with stucco performance on commercial buildings and explores the reasons for the difference in performance between residential and commercial stucco applications. We also make suggestions for improved stucco performance on commercial buildings.