Forensic Analysis of Construction Variances Associated with Cement Plaster (Stucco) Veneer Installed Over Wood Framing

Abstract

The International Residential Code (IRC) provides prescriptive specifications for the installation of cement plaster (stucco) veneer on wood framing. Since 2006, the IRC has also referenced ASTM C926 (Standard Specification for Application of Portland Cement-Based Plaster) and ASTM C1063 (Standard Specification for Installation of Lathing and Furring to Receive Interior and Exterior Portland Cement-Based Plaster) as applicable standards that provide additional specifications associated with the installation of cement plaster veneer. The IRC and the applicable code-referenced standards do not consider all available materials, designs, and/or methods of construction — nor do they consider possible alternatives or construction variances. Since there is more than one way to accomplish a goal, a forensic investigation should consider the intent and purpose of a specification (i.e., the desired performance) to determine whether an as-built alternative or construction variance is capable of accomplishing the same without adversely affecting a structure. This paper explores common construction alternatives and variances associated with the installation of cement plaster veneer (including control joints, attachment, thickness, and clearance) using methodologies for evaluating whether an alternative or variance can still achieve the intent and purpose of the specifications provided in the IRC and/or applicable code-referenced standards.