The recent changes to commercial building codes have caused cascading complications relating to how we construct building enclosures. This has resulted in some of the “old methods” of cladding installation no longer meeting the current code in some locales. The introduction of continuous exterior insulation requirements with thermal breaks, air barriers and NFPA 285 requirements for water resistive barriers, have left many design professionals uncertain as to what is the correct design for a code compliant assembly that will produce a long-lasting installation that is free from water intrusion leaks. By emphasizing commercial rather than residential building assemblies, this article will shed new light on a long-standing complex and convoluted topic.
Let’s begin by examining traditional three coat stucco over lath, a common cost-effective cladding material used extensively in the Southwest region of the United States and elsewhere in North America. Light commercial and multi-family structures are often clad with this material. Stucco is commonly installed over wood framing with plywood sheathing, or steel framing with gypsum sheathing back-up walls. Stucco is arguably low maintenance and adaptable to both classical and modern architectural styles.