Sealants Aren't Exactly a Science

By: David Neal

How do companies like Chamberlin know what sealant products to choose for installation or how to fix oh-too-common sealant failures? It’s a process that requires an immense amount of product knowledge and detailed review of the project requirements and joint design. In fact, when it comes to sealants it’s sometimes easier to make a bad decision than it is to make a good decision without a full understanding of the project needs and the sealant choices available in the marketplace.

Technically speaking, sealant failure is “the loss of the ability of a sealant to serve as an effective barrier to the passage of water and air.”  Sealant failures are typically categorized as adhesive failure, cohesive failure, substrate failure or degradation of the sealant properties inhibiting the sealants’ ability to perform as designed. Unfortunately, these problems are not uncommon. Often, the discovery of water in an inconvenient place is the result of just such a sealant failure. Perhaps the complexity of choosing and applying sealants is one reason why.

CHOOSING A SEALANT

Unfortunately, there is no single sealant that’s perfect for all applications. To avoid joint (sealant) failures construction professionals must not only select the proper sealants, but also determine the proper joint design to accommodate the anticipated joint movement. They must install the sealants in the appropriate bead configuration, insuring the proper depth and width of sealant. Further, an adhesion test should be conducted to ensure proper sealant adhesion to the various substrates on that specific project.

Though there are reference standards for installation and selection, such as ASTM, they actually provide only limited guidance and each project must be reviewed individually. Making a decision regarding which sealant to use involves prioritizing and analyzing a wide array of characteristics and benefits. Relevant criteria can include things like, type of substrate sealant will be adhered to; proper sealant primers; resistance to chemicals such as fuel; stability in adverse conditions like acid rain; life expectancy considering weatherability and UV stability; physical characteristics such as hardness, flexibility and density; color options for appearance sake in visible areas; cost issues such as value for the dollar and warranty; and the list goes on. These considerations only skim the surface of what are literally hundreds of variables that can come into play.

When choosing a sealant, professionals are in many ways left to their own knowledge and experience; a little common sense, expertise and the ability to prioritize sealant characteristics to determine the right sealant for the job at hand. Unfortunately, our own devices aren’t always the most effective or scientific. As a result sealant failures do happen. The variability of the characteristics to be considered and products available makes a construction company’s job extremely difficult. And, unfortunately, variability is also an issue when addressing a sealant failure.

THE ROOT OF THE PROBLEM

Determining why an existing sealant joint failed involves more than a visual inspection of the sealant to determine the root cause of the failure. If a joint fails at a young age (1-2 years after installation) it is likely an issue of one of three things: design, material specifications or workmanship. When this occurs there seems to be a lot of questions as to where the issue really lies. Workers tend to point to the joint design or manufacturer’s materials. On the contrary, the manufactures point to the workers’ installation or the intended design. Perhaps the wrong product was specified from the get go, or the right sealant was specified but adhesion tests were not performed to determine the correct primer to be used prior to installing the sealant, or the joint sizing was incorrect, or excess joint movement occurred…the list goes on.

Regardless of the cause, the problem needs to be fixed. And, to add insult to injury, the truth of the matter is that while there is often a dominant cause to the problem that does fall into one of these three categories, addressing just one almost never alleviates the problem. Sealant failures are usually a combination of a long list of variables that need to be considered.

If a joint fails after an extended period of time, gradual deterioration is usually attributed to the breakdown of the sealant or substrate and can be categorized as an adhesive failure, cohesive failure, substrate failure or incompatibility of sealant properties. All four of these categories, of course, are also host to a long list of possible problems.

A COMPOUNDED ISSUE

In an effort to help avoid these kinds of failures, new technologies are continually being developed to enhance sealant products. As a result, the issue of choice and repair is continually becoming more complex. As more specialized products become available, choices are compounded rather than consolidated.

At one time, not so long ago, it was easy to determine the different applications most suited for silicone, polyurethane, butyl or acrylic. But that’s far from the case today. Now, more than ever, construction professionals have to have an in-depth knowledge of the products available, their ideal uses and application processes. Clearly, making the right decision to install or repair a sealant can be extremely complex. A contractor, such as Chamberlin, must consider all the variables associated with the process, including all potential and plausible needs, then take action based on informed decisions.