Water Management in Exterior Wall Claddings

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This paper presents results of laboratory testing on the performance of wall claddings using direct-applied (DEFS) and exterior insulation finish systems (EIFS) that incorporate water management features into their design and construc tion. The work presented in this paper is a continuation of earlier work conducted by the Institute for Research in Construction (IRC) of the National Research Council, Canada (NRCC) and the United States Gypsum Company (USG) evaluating the water penetration and moisture performance of barrier EIFS clad walls (Brown et al., 1997). Direct-applied exterior finish systems (DEFS) are exterior wall claddings that use a water durable substrate, typically cement board, mechanically fastened to the wall framing over a sheathing membrane. A cementitious basecoat and textured acrylic synthetic stucco finish is then applied directly over the substrate. Insulation for the DEFS system is in the stud cavity. EIFS systems use a layer of foam insulation applied over the wall substrate, with basecoat and finish applied over the foam. The performance of three water managed wall cladding designs in protecting wood framed construction from water intrusion by wind-driven rain is described. Three different drainage systems were evaluated. Performance measures evaluated in cluded cladding airtightness, pressure equalization potential, and water drainage under wind-driven rain conditions. In each of the three systems, partial pressure equalization was observed, and any water that did breach the exterior skin was stopped at the sheathing membrane and directed down and out of the wall through the flashing and weep openings.