Exterior Insulation Finishing Systems have garnered themselves a poor reputation with regards to water intrusion. It's widely-known in the industry that these problems are caused by improper installation, and one of those forms of improper installation is not using adequate sealants or installing sealants properly. If sealants are not used effectively where the EIFS terminates or meets components such as windows and flashings, water intrusion is a risk the EIFS might face.
Materials used with sealants
The material the sealant is applied to is pivotal for adequate adhesion and the repelling of water. The lamina of the EIFS itself and materials such as wood are not very compatible with most sealants because they're porous, but nonporous materials like glass, some metals and some types of stone provide a great surface for sealants to grab on to. Wood is especially not compatible with sealants, even if it's treated or sealed. The reason for this is that wood is especially vulnerable to thermal shifting, which will eventually "unhinge" any sealant that is applied. A sealant applied directly to the base coat of an EIFS application, as long as the joint is properly designed and the sealant is applied properly, will produce an optimal and long-lasting joint.
Manufacturers produce many different types of primers that can assist with sealant adhesion to the EIFS joint, but be careful. If the joint is being placed between EIFS and another component, such as trim made of non-EIFS material, the primer may not be designed to create adequate adhesion to the other material. This is the first consideration to keep in mind when using a primer.
The second consideration to keep in mind when using a primer is that it can create a colour difference between areas of the EIFS. Because the joint should be applied directly to the base coat, the primer must be too. If any primer remains visible after the installation it can change colour when exposed to sunlight. Because of this, the primer should be completely covered, either with sealant or more EIFS lamina to prevent any discolouration. Primers are also not unique to EIFS, as many other materials end up needing a primer for optimal performance in one way or another.
Moisture and sealants
Different components of EIFS react differently to moisture. The lamina, for example, may soften and absorb moisture, but base coats will provide a much stronger surface for sealants to adhere to. In some instances, not bonding the sealant to the base coat can void the EIFS manufacturer's warranty and the practice of bonding the sealant to the base coat has been the accepted industry standard for the past 30 or so years.
Choosing a sealant
When using any non-EIFS material or component with an EIFS product, it's important to ensure the material is suitable for use with EIFS especially when there's an abundance of choice in the matter. This may mean following manufacturer instructions and discussing the ramifications of sealant choice with the manufacturer directly, or they may have a list of acceptable sealant products you could take a look at.
If the sealant manufacturer differs from the EIFS manufacturer, follow each separate set of directions closely. Not doing so could void any warranties on the products. If the sealant is not made for EIFS at all, test runs should be conducted under both poor and optimal weather conditions to ensure it will hold up and stand the test of time. Non-EIFS sealants that tend to match well with EIFS applications are flexible and don't stretch beyond their capability to "bounce back" to their original shape. They should also be able to withstand the extreme cold of Ontario winters without hardening to the point of possible breakage when a building shifts.
The correct size of a joint is important. If the joint is too small for where it has been placed, or doesn't exist where one is needed, it's not installed properly. All installers of EIFS should be aware of the possible repercussions of not installing adequate joints with proper sealants.
Sealant problems can be common with EIFS, and as previously mentioned improperly installing sealant at joints or terminations can result in a leaky wall. Sealants can become old, differ in texture, not be suited for use with EIFS or not be present at all in preexisting EIFS applications. Sealant can even be found to have been adhered to the lamina instead of the base coat as recommended, however if this hasn't produced a leak thus far, it could be okay to leave as is.