The use of exterior insulation finish systems (EIFS) has grown dramatically in recent years, in both commercial and residential markets, accounting for more than 200 million square feet of building exteriors in 1991. The systems, sometimes called "synthetic stucco," are economical and give designers a lot of flexibility with colors and architectural details. In addition, they provide good insulation without thermal gaps and greatly reduce air infiltration. Of the two generic types of EIFS, polymer-based (PB) and polymer-modified (PM), the PB systems are by far the more commonly used in the U.S. today. PB systems, sometimes called "soft-coat," are typically thin (approximately 1/8 inch total thickness), adhesively attached, and flexible, and they require few control joints. They cannot tolerate prolonged wetting. PM systems, on the other hand, are typically