Sealants, Part 2: your silent partner on the job

Sealants are a hidden part of what goes on inside and outside of a building, but they have become an integral silent partner in the building process. As a builder, you could choose the wrong one or apply it the wrong way, and find yourself kissing your profits goodbye if the sealant fails.

OSI Adhesives & Sealants

Photo courtesy of OSI

Paul Majka, applications engineer for Henkel Corporation-North America, parent company of OSI Adhesives & Sealants, explained the importance of making good choices.

“As far as sealants go, the builder/contractor and window/siding installer play a critical role when it comes to making the right choices,” he said. “This is crucial to sealant application and performance. Consider the multitude of exterior finish materials and coatings that are used in building design, then combine that with variations in window frame cladding types. The sealant that is used to seal out air, moisture and water between these materials must provide reliable adhesion, flexibility and durability against a wide range of weather conditions.

“In regards to exterior steel cladding, on our post and frame agricultural buildings, there are a number of coatings and finishes—Galvalume, Zincalume, Kynar—and the sealant we use must bond to each one without failure.”

Bill Sobonya, brand manager for Henkel, agrees. “The substrates that have evolved in our industry have put a ton of pressure on the performance of sealants and a lot of the brands and technologies haven’t kept pace with the change in those materials,” he said. Builders today need to know “the relevant substrates that the sealant has to stick to not just from a short-term standpoint but from a long-term standpoint.”

It’s a challenge. “Builders and installers are approached with new products and innovations for exterior and interior applications constantly,” said Majka. “People that represent these products promote their specific design and performance features, and how they will possibly offer ease of install or cost savings. Maybe it does have all the things that can work for the project’s design but … if there is any caveat or caution to contractors: make sure … that any new product will not only work with the application used for the design of that building envelope. Consider all the products that will be used to integrate that system, and that together the assembly of all parts provide the reliability and durability that is expected.”

Not taking the precaution can have consequences. “A contractor is at risk if that building fails,” Majka said. “So the contractor should take the performance of the zipper (which is really the sealant) of the building into account. Make sure they have the right product that will perform well, that includes the sealant’s compatibility, adhesion, flexibility and durability, because it’s their liability and it’s their integrity and it’s their credibility that’s on the line.”

Sealant vs Application
There are primarily two ways that a sealant can fail:

  • A high quality sealant installed incorrectly
  • A low quality sealant that won’t perform regardless of how well it’s installed

Sobonya offers more specifics. “If we just look at windows, for example, one of the of the most difficult materials to bond to a window is fiberglass. When you look at cladding, in the traditional cladding market fiber cement is a difficult material to stick to. In [the metal] industry, the paint coating, the Kynar, the Galvalume on the substrate, is very difficult to stick to.

“With metal, there is a lot of expansion and contraction, especially at the window penetration where you want the sealant to bond properly, but also you want it to expand and contract with the temperature changes as the metal expands and contracts. There are a couple of things that can happen. You can have loss of adhesion to the substrate or you can have loss of adhesion through the sealant itself where the sealant tears itself apart … That’s where you can get water to start to flow into the building and cause damage, or air infiltration and exfiltration which will compromise the energy efficiency of the building.”

Majka breaks down the most important areas that installers need to pay attention to into 18 different parts. Without identifying each one separately, they primarily relate to what types of finishes or surfaces the sealant is expected to bond to; the movement of the wall system or materials and the sealant’s flexibility (being able to adapt to the wall assemblies expansion and contraction); the type of joint, the climate during the application process; and the environment the sealant and sealant joint will be exposed to after application (water, air or UV light).

“If the wrong sealant is applied or applied incorrectly it can fail,” he said.

In regards to movement, Majka gives this example: “Say for instance you’re installing panel steel siding. Steel panels can move a lot, especially on a south side of a building with sun exposure. Then add vinyl windows that are installed into that wall … The builder should ask, what sealant should I use here? The contractor needs to ask these questions: will the sealant provide me with the compatibility, movement, adhesion and durability expected considering all the wall assembly, joint design and also the environment in which it’s going to be exposed to?”

Once determined, the builder needs to make sure the sealant he chooses meets all the needed criteria.

Bottom line, do your homework ahead of time and don’t discount the science of sealants.

Concluded Majka: “When a builder looks at a plan, it could be an agricultural building or it could be a precast masonry building, it doesn’t matter, they have to think about exactly what they are applying that sealant to, and to make certain they understand whether or not that sealant is going to perform, and if not the ramifications they’re going to be exposing themselves to.” RB


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