When designing and installing EIFS, one of the most important things to pay attention to is the interface between the EIFS and adjacent wall components at the perimeter of the EIFS. This includes ever-present locations, such as windows, doors, penetrations, flashings, surface-mounted objects and so on. Since EIFS is essentially a jointless system, the only place for water to get into the wall is at the edge of the EIFS and hence is the No. 1 spot to look at when investigating water intrusion issues. The point is that the interface needs to be carefully designed and executed. Sealants, along with flashings, are the main line of defense at interfaces and it's worth the time to review how EIFS sealant joints should be done and also to understand the history of the evolution of EIFS sealant joint design.
From a sealant compatibility standpoint, the EIFS lamina is neither a nonporous or porous material, or "sealant substrate." For example, aluminum and glass are nonporous, while some types of wood and stone are porous (the term "porous" here means water absorptive to some degree). Strong, nonporous surfaces, of the type that the sealant can get good adhesion to, make the best substrate for sealants. Some nonporous substrates, such as some paints that repel water, are difficult to adhere to since the sealant cannot get a good grip on the surface without some help, such as a sealant primer. Unstable materials, such as raw or treated wood, which expand and contract a lot, are often difficult to bond the sealant to and soft, weak materials, usually make poor sealant substrates.