Improving Stucco Durability Using Moist-curing by Nickie Ramm, EIT Photos courtesy Building Diagnostics Inc. OBSERVATIONS OF NUMEROUS BUILDING ENVELOPE FAILURES IN STUCCO (I.E. PORTLAND CEMENT PLASTER) INDICATE IT MAY LACK DURABILITY WHEN CORRECT INSTALLATION PRACTICES ARE NOT PERFORMED. ONE OF THE MOST COMMON PROBLEMS IS CRACKED STUCCO—AND WITH THE INCREASING TREND OF USING THE MATERIAL AS A CLADDING, THE SITUATION WILL LIKELY GET WORSE. Historically, stucco has been a durable material, so cracking is not inherent; rather, the observed distress results from design and construction errors such as poor consolidation, inadequate control joints, or non-uniform thickness. Hydration is essential to achieving durable stucco. It is the principal mechanism of converting portland cement into a solid binder. Improper hydration leads to decreased strength development, layers’ delamination, and cracking. Hydration is attained by incorporating proper curing methods during 56 the construction specifier | january 2013 CS_Jan2013.indd 56 12/12/12 9:34:58 AM