Adhesives and Joint Sealants in Construction: Types & Differences

Industries that use both sealants and adhesives have built up a long list of products and terminology. In commercial construction, that doesn’t mean you should use either interchangeably.

These two construction materials are similar on a fundamental level, but serve different primary goals. To get the proper level of protection and performance in your application, you’ll need to know each a little better.

Below, we’ll cover the important basics subcontractors need to know:

• The differences in each product
• Pros & cons of each
• When to use adhesives vs. sealants

What Is the Difference Between Adhesives and Sealants?

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

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:

• Air
• Dust
• Sound

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:

Adhesives

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:

• Less labor investment – no curing time
• Greater range of material options for design
• Adheres to traditionally challenging surfaces
• Can immediately be transported or stored vertically, saving space

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.

Pros & Cons: Sealants and Adhesives in Construction

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:

Installation

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.

Strength

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.

Bonding

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.

Weather Exposure

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.

Movement

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.

Chemicals

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.

Aesthetics

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.

Uses for Construction Sealants & Adhesives

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.

Uses of Sealants in Construction

Sealants are a must on every new construction job and many restoration applications, such as:

• Deck coatings
• Expansion joint replacement
• Crack repair
• Window replacement

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:

Uses of Adhesives in Construction

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:

• Concrete & masonry – structural walls, facades, and retaining walls
• Transportation industry (polyurethane)
• Weatherstripping (butyl)
• Subflooring

Function Meets (Your) Application

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: