Design of Engineered Drainable Exterior Insulation and Finish System (EIFS) Cladding

Abstract

Abstract During the last ten years, the authors have investigated a number of buildings with leakage and deterioration problems associated with exterior walls clad with exterior insulation and finish systems (EIFS). These systems were “barrier” walls applied to materials that degrade rapidly from exposure to moisture, such as gypsum board sheathing. These wall systems lacked backup waterproofing and flashing elements and relied on surface seals as the sole means of controlling water penetration (leakage). While these systems are appealing due to their aesthetic features, light weight and insulating characteristics, they are vulnerable to performance problems as a result of failed surface seals, leakage through window frame corners and poor installation practices. Installation of internal flashings is difficult at best because the primary waterproofing layer (the lamina) is on the face of the cladding rather than in the plane of the flashing. In this paper, the authors review the essential differences between barrier and drainable EIFS. The primary focus of the paper is to examine the various components of an engineered drainable EIFS including waterproofing membranes, drainage plane grids, methods of attachment, and consideration for use of a vapor retarder (position) within the wall cross section. Detailing of wall penetrations, particularly for windows and doors will be presented as will location of flashings and weep mechanisms in multi story construction. Design considerations will be illustrated in two case studies where barrier EIFS was replaced with an engineered drainable system, one in a relatively warm climate (southern California) and the other in a relatively cold climate (Massachusetts).