Industries working with both sealants and adhesives have developed extensive product lists and terminology. In commercial construction, however, the two shouldn't be used interchangeably.
While these two construction materials share some basic similarities, they serve distinct purposes. Gaining a clearer understanding of each is important for achieving the right protection and performance in your application.
Below, we’ll cover the important basics subcontractors need to know:
More like differences. On the surface, comparing the function of silicone adhesives vs. silicone sealants is simple, but there are many shades of gray beyond their true colors.
Sealants consist of a flexible material that usually contains an elastomer. The chemical structure creates a paste-like consistency that makes it perfect for filling gaps between component surfaces. These are materials that, first and foremost, prevent liquids from passing through joints or openings. Sealants also help surfaces accommodate movement.
They also provide a barrier to keep out:
As if things weren’t confusing enough, builders and companies often use “sealants” and “caulk” interchangeably when they refer to a product that blocks moisture and air. Without getting too off-track, here’s a look at the differences in two typical products:
|
Caulk |
Sealant |
|
|
Material |
Solvent- or water-based |
Elastomer |
|
Movement |
Minimal |
More |
|
Shrinkage |
Prone during curing |
Minimal |
|
Weatherability |
OK |
Better |
Adhesives join two surfaces, providing structural stability through bonding.
Can an adhesive be a sealant? Some of them, yes, but that’s not the primary function.
Adhesives can take the form of epoxy, glue, liquid, paste, film, and pellets. One of the most prominent types of adhesives that subcontractors use is tape. This isn’t your father’s Scotch or duct tape – some construction tapes can replace screws or anchors, holding building elements structurally in place.
Many designers, manufacturers, fabricators, and installers elect to use tapes over sealants, or even other adhesives, due to:
With so many types of adhesives, you should be able to find something that withstands wind, temperature, vibration, and other challenges your application might face.
As always, your choice of construction adhesives and sealants will largely come down to your application. Here are the factors to look for in yours:
The ease or complexity of installation is probably the biggest factor for those choosing between a structural sealant and a structural adhesive.
Sealants may be more forgiving when trying to apply them. If you’re assembling a wall on-site, for example, you’re probably better off with sealant.
Adhesives often require surface preparation and precise application. However, the degree of difficulty goes way down if you use it in-factory. An example would be using tape when manufacturing a curtain wall system.
Sealants tend to offer less support and stiffness between two substrates. This isn’t always a bad thing, as you’ll learn in the Movement section. That said, there are structural “adhesive” sealants (a mildly misleading term) that excel in building joints with large bearing capacity.
Adhesives are generally higher-strength, with lower elongation at break. Products with low elongation are great for creating a rigid connection in structural elements you don’t expect will move much. Just don’t mix up, say, a structural bonding tape with a non-structural adhesive meant for decorative use.
Sealants have adhesive properties, but they’re not necessarily true “adhesives.” You wouldn’t hang a mirror on a wall with Dowsil 795 silicone sealant or urethane caulking. Due to their chemistry, sealants rarely provide sufficient bonding force to hold objects together. Even claiming silicone sealant as an “adhesive” does not make it a good adhesive.
Adhesives, you may have guessed, specialize in sticking to a substrate. Note that adhesion (bonding) and cohesion (strength) aren’t the exact-same thing. Nonetheless, their bonding abilities make them popular in applications where structural integrity is a priority. You could certainly use a mastic adhesive to hang that wall mirror.
Sealants are formulated to fill gaps between the surfaces of components. This allows them to form waterproof and airtight barriers.
Adhesives don’t bond well in low temperatures, though there are specialized products for cold environments. Ask your supplier about weathering tests for adhesives to ensure they’ll perform as advertised in your environment. On the major-plus side, many silicone adhesives can also function as a sealant, limiting water absorption and helping seal gaps as temperatures rise.
Sealants are a poster child for flexibility and the ability to withstand movement. Their general pasty consistency makes them ideal for filling joints and gaps that may expand or contract.
Adhesives often become brittle as they dry, which increases their odds of cracking in high-movement applications. Their general lack of elasticity means you’ll need to find a special-use adhesive in cases where you’re about maintaining strength during surface tension.
Sealants, despite being a great barrier against moisture and air, don’t always offer the same level of resistance to chemicals. as specialized adhesives. However, certain types of sealants (i.e. silicone) are specially made for corrosive environments. Always consult product specifications!
Adhesives, particularly those that are chemically cured, can provide strong resistance to a variety of corrosives. This makes them suitable for exposure to oils, solvents, or acids in industrial settings.
Sealants for construction often come in a wide variety of aesthetics. Your distributor may offer custom color matching and tinting options. These can make connections between components so seamless that no one will notice them.
Construction materials face unique environmental conditions all over America, plus an endless variety of project requirements. Here’s where you’ll commonly find wise use of sealants and adhesives.
Sealants are a must on every new construction job and many restoration applications, such as:
Structural sealants act as a support for glass, ceramic, metal, and composite panels. There are specialty sealants with even more specific jobs, some of which you’ll see below:
|
Sealant Type |
Material |
Example Use |
|
One-Component |
Silicone |
Household caulking |
|
One-Component |
Urethane |
Marine repair |
|
One-Component |
Acrylic |
General-purpose metal & plastic bonding |
|
One-Component |
Butyl |
Roofing |
|
One-Component |
Polysulfide or SMP (shape-memory polymer) |
Windows |
|
Two-Component |
Urethane |
Glass bonding |
|
Two-Component |
Silicone |
Encapsulation |
|
Two-Component |
Intumescent (fire mastics) |
Fire barriers |
Adhesives were born to shine in confined, unexposed areas.
In these spaces, both traditional and newer construction materials need products that promote adhesion and performance, while remaining easy to apply. This stands for concrete, wood, plastic, and more.
Specifically, tapes are common in glass, glazing, and metal panel applications. If you plan to do commercial glazing or even residential window manufacturing, you’ll absolutely need tape.
Other examples of adhesives in commercial construction include:
|
How do the performance and durability of adhesives and sealants compare in extreme weather conditions? Adhesives and sealants perform differently under extreme weather conditions due to their distinct properties. Sealants, particularly those made from silicone or urethane, are designed to remain flexible and maintain their sealing properties despite temperature fluctuations, making them well-suited for applications exposed to varying weather. They can handle expansion and contraction without losing their effectiveness. Adhesives, especially those not formulated for extreme conditions, may become brittle or lose their bonding strength in very low or high temperatures. Specialized adhesives are available for cold environments or high-temperature applications, but it’s crucial to select the right product based on specific weather conditions and application requirements. What are the recommended methods for disposing of or recycling used adhesives and sealants? The disposal and recycling of used adhesives and sealants depend on the type of material and local regulations. Many adhesives and sealants are considered hazardous waste and should be disposed of through specialized waste management services. For latex or water-based products, local municipal waste disposal programs might accept them. Some manufacturers offer take-back or recycling programs for their products. It’s important to check with the manufacturer or local waste management authorities for proper disposal procedures to ensure environmental safety and compliance with regulations. How do specific adhesives and sealants impact the long-term maintenance of construction projects? The choice of adhesives and sealants can significantly influence the long-term maintenance of construction projects. Sealants that are well-matched to their intended use can prevent water infiltration and protect against environmental damage, reducing the need for frequent repairs. However, if a sealant fails or is improperly applied, it can lead to issues like mold growth, structural damage, or energy inefficiency, requiring costly maintenance. Similarly, adhesives that are not suited for the environmental conditions or the materials being bonded can degrade over time, leading to weakened joints and the need for replacements. Choosing high-quality products and ensuring correct application can minimize maintenance needs and extend the lifespan of construction elements. |
What’s the right way to talk about construction adhesives and sealants?
For commercial applications, the simple answer is that an adhesive bonds surfaces structurally, while a sealant makes joints and gaps weatherproof.
Of course, some adhesives and sealants are better suited for extreme conditions. And sometimes you can in fact use an adhesive for weather sealing.
This is a great opportunity to lean on your distribution expert for proper use (or find one if you don’t have one). Your supplier should be able to marry project and product seamlessly.
In the meantime, continue your own product and material education at our resource center:
This blog was originally published in Dec. 2023 and was recently updated