Well, That is What He Told Me…

Words: Steven Fechino

As part of my job, I get the opportunity to have contractors, architects, and engineers discuss challenges that they face on the projects they are working on, and usually, they ask for advice. My job is easy; I am on the outside, basically without a dog in the fight. What happens often is that the folks who call me are second-party customers for the products they design with. What I mean is they design or build with a product using the information that was presented either by technical documents found on the manufacturer's website or from information presented to them by a local sales agent.

The designers typically work with really good and accurate information, but sometimes it can be complicated and misunderstood. Here is a common example that I often discuss: sealants vs. caulking. These products are interchangeable in job site discussions, but the products are very different.

Caulking is not intended to be used in an exterior application because of the chemical composition of the product. Generally, caulking is made using latex, acrylic, and clays to formulate the product. Caulk is typically not very elastic, but where the actual movement of the joint is very small when in service. The capability of caulking joints is approximately 10 percent compression and 10 percent elastic movement. The product can flex more than that, but that is unrealistic for this product. Caulk is a common product used in interior build-outs, trim touch-up, and overall interior door jamb seal applications. Caulk does not necessarily fall into the joint-to-width ratio (which I will discuss in more detail shortly) as a typical application can be as small as three-sixteenths of an inch of material to just a dab.

Sealants are an entirely different product. Sealants are typically used as an exterior application in framing, masonry, EIFS, and many other trades using products to seal exterior penetrations. Sealants can be purchased in many different formulations, ranging from non-curing synthetic rubber butyls, modified silicone polyether, silicones, polysulfides, and even still polyurethane elastomerics. All of the types of products that I just noted all have different serviceable applications with very little crossover between products. Silicone is a composition unlike the others listed; silicone can be installed in very little joint-to-width ratios, 1:1, and it can be as small as a quarter-inch by a quarter-inch, the smallest of the ratios. Silicone is typically not a paintable joint, so colors need to be selected. It is solvent-based and has a long service life. This product is perfect for granite, marble, glass, and anodized aluminum joints. Select with care when the joint you are sealing has dissimilar materials.

For example, anodized aluminum to wood window perimeter; another choice of sealants may offer better service. Polysulfide sealant is an older sealant that many folks may not be familiar with. Last used commonly in the 1980s, polysulfides were a great choice for stone veneer high-rise structures that would be difficult to access over the life of the structure for inspection or repair. As the sealant was like a bee’s wax type feel, it has a very long service life, but accessing the materials to formulate the product, color options, and installation were replaced with the polyurethane elastomerics of the 1990s.

Today, we commonly see a product called polyethers for use in many masonry applications.Polyether is a modified silicone product that has superior capabilities over polyurethane elastomeric products. The polyether may cost a few cents more than polyurethane elastomerics but has a longer service life ranging from three to five years (actual time, you may get longer based on exposure). It is a paintable product and typically does not have the gassing issues that polyurethanes experience.

Sealants do have special conditions that are common to all: install the joint too thin, and it will crack over time down the middle. This is a cohesive failure because the sealant does not have enough material to properly contract and expand.

Install it too thick and you will have an interior failure, still cohesive, but harder to detect as the internal stress of the movement basically just rips the joint on the inside from movement. Adhesive failure is basically where it "just ain't gonna stick, brother," no matter what you do. Properly matching the sealant to the substrate is critical. Here is where you can talk to the local sales guy or call the sealant manufacturer’s technical support line and get information that you can design and build by (you can with sales guys, but the technical guy who has a limited personality, just like myself, will have raw numbers and data you can bank on). If the surface energy is not matched to the sealant, you are wasting time. Sure, it will stick when applying, but will it be there in two weeks? Sealant joints must be designed in a 2:1 width to depth ratio. To accomplish this, you typically fill the joint prior to sealing with a backer rod material.

Personally, I like the soft rod over the closed cell foam as it does not puncture or tear as fast as closed cell foam and also limits the gassing of the sealant joints. Joints need, and I mean need, to only adhere to two points in a joint. Sealant is designed to move in two directions, in and out. If a sealant joint is contacting three surfaces, the triaxial stress will destroy the joint in a short period of time, and this costs money to all.

When trying to understand the complex nature of a design or product, call the folks who are there to help you get the job done without you having product knowledge stress. If I need to know something about a product, I call and get tech support. The tech support is free and always helpful as today many products that we use are more complex in chemical make-up, compatibility, and applications. This information may be a new resource in your bag of tricks but could also really save you money in the long run.

It looks like it is going to be a busy year with a lot of work coming out in the next few months. Pace yourself; it is a marathon, not a sprint. The work will be there. Be patient and select the work you can make the most money at, something I tried to do every time. But...remember, it is a marathon. Do not try to be like me sometimes.

Well, That is What He Told Me…

About: Fechino Files

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