Don't want to face the costly challenges of building failure and water damage?
Sealant incompatibility is one of the most common construction errors that result in leaks, cracks and damage to building budgets. The simple truth is not every sealant works with every material.
The good news is this:
Understanding sealant compatibility is not difficult when the basics are explained. Once you understand compatibility, it's easy to save thousands in future repair costs.
In This Guide We Cover:
What Sealant Compatibility Really Means
Why Material Matching Is Critical
The Most Common Sealant Types Explained
Which Sealants Work Best With Different Materials
How To Test For Compatibility
Let's get to it!
What Is Sealant Compatibility?
Sealant compatibility is how well a sealant adheres to and performs with certain building materials.
Compatibility of a sealant with a substrate means that it bonds properly and maintains a seal throughout its design life. Incompatibility, on the other hand, means that there are problems.
Compatibility problems can cause:
Adhesion failure (pulling away from the surface)
Discolouration and staining
Chemical reactions that break down the sealant
Complete seal failure and water intrusion
According to industry research, the building and construction segment accounts for approximately 62% of the global sealant market. The volume of sealant being applied to buildings around the world is vast. The fact is, a significant portion of sealant and adhesive failures can be traced back to compatibility problems.
In selecting quality sealant and adhesive solutions, suppliers like Strathclyde Sealants have the expertise to guide customers in matching products to specific applications. The right match up front avoids problems down the line.
Why Material Matching Is Critical
Think about what occurs when a building joint fails.
Water intrusion occurs. Mould growth. Structural damage. What was a small oversight at installation becomes a major renovation headache.
Thing is…
Sealant failures are rarely random. In fact, there are seven common causes of sealant failure in the construction industry according to industry experts. The most common ones are caused by incorrect sealant selection, inadequate surface preparation, and substrate incompatibility.
The global sealant market size is expected to reach $22 billion by 2030 as a result of the surge in the construction industry. With billions of dollars of sealant being applied, year in and year out, compatibility takes on even more importance.
The bottom line is this…
Matching the right sealant with the right material is not optional. It's a necessity if long term building performance is desired.
The Main Sealant Types Explained
Before we get into compatibility, let's first take a look at the most common sealant types that are available today.
Silicone Sealants
Silicone sealants are the most widely used sealant in the industry. They provide excellent flexibility, UV resistance and can withstand extreme temperatures.
They work especially well on glass, metal and many plastic surfaces.
The problem is, they won't bond well to all surfaces. In fact, porous materials like concrete and masonry usually need a primer before silicone. Silicone sealants will also stain natural stone.
Polyurethane Sealants
Polyurethane sealants offer good adhesion to a wide variety of materials. They are paintable and work well on concrete, wood and metal.
The disadvantage is that they do not fare well against UV exposure like silicone. Exterior applications may need a protective coating on top of polyurethane sealants.
Acrylic Sealants
Acrylic sealants are the most economical type and are easy to apply. They can be painted over and clean up with water.
They do have some limitations. Acrylics are not recommended for high movement joints or wet environments. These sealants can shrink and crack over time if used in demanding applications.
Polysulfide Sealants
These sealants work best in below-grade applications and areas exposed to fuels or chemicals. They are commonly used around fuel storage tanks and industrial buildings.
Polysulfide sealants require more surface preparation than others and have a longer cure time.
Which Sealants Work With Which Materials?
This is where the rubber (or silicone) meets the road. Different substrates require different solutions.
Glass and Metal
Silicone sealants are typically the best choice for glass and metal. Silicone provides good adhesion without the need for primers in most cases. Neutral-cure silicones are the way to go here as they don't release corrosive byproducts during the curing process.
An important note is that acetoxy-cure silicones (the ones that smell like vinegar) can corrode bare metals like aluminium, copper and zinc. Check the chemistry before using these sealants.
Concrete and Masonry
Polyurethane sealants generally perform best on porous substrates such as concrete and masonry. They are able to penetrate into the surface and create a strong mechanical bond.
Silicone can also be used but often requires a primer. Without primers and proper surface preparation, adhesion failure is common on these materials.
Wood
Wood is a little more challenging because it expands and contracts as moisture levels fluctuate. Polyurethane and hybrid sealants are the best for this movement.
Rigid sealants will not work on wood joints. The natural expansion and contraction will crack them over time.
Plastics
Plastics are always tricky. Certain sealants can react badly with some plastic formulations causing crazing, softening or bond failure.
Always test sealant compatibility on a small area first before committing to the whole project. This is especially important with PVC, polycarbonate and acrylic plastics.
How To Test For Compatibility
Testing compatibility before full application is not an option. It's a necessity.
The approach is straightforward.
Apply a small amount of sealant to an inconspicuous area of the substrate. Allow the sealant to cure per manufacturer's instructions. Then check to see that it has fully adhered properly with no discolouration or adverse reactions.
For critical applications, more rigorous testing according to AAMA 713 chemical compatibility testing standards can be performed. AAMA 713 is a good option for an in depth look at how sealants and tapes interact with building wraps, flashings and other building materials.
Additional tips:
Always clean surfaces thoroughly before testing.
Allow full cure time before evaluating test results.
Test all materials the sealant will contact, not just the primary substrate.
Document test results for future reference.
Not too hard is it?
The Compatibility Quick Reference
To make it even easier, here's a simple quick reference for some of the most common material and sealant combinations:
Material | Best Sealant Options |
|---|---|
Glass | Neutral-cure silicone |
Aluminium | Neutral-cure silicone, polyurethane |
Concrete | Polyurethane, modified silicone |
Wood | Polyurethane, hybrid sealants |
Natural Stone | Neutral-cure silicone (test first) |
Plastics | Test required for each type |
This table is a general guide only. Always verify compatibility for specific applications and products.
Pulling It All Together
Sealant compatibility isn't rocket science when the basics are understood. At its most basic, it's simply matching the right product to the right material.
Recap:
Sealants are not all the same. Different sealants have different chemistry.
Not every sealant works with every substrate or material. Testing prevents failures.
Always test sealant compatibility before full application.
Surface preparation is just as important as the sealant product selection itself.
When in doubt, read manufacturer guidelines or talk to a technical expert.
Getting this simple step right prevents water damage to buildings, extends the life of construction joints and building movement joints, and saves money on costly repairs.
The sealant and adhesive industry continues to grow because these products are a necessity in modern construction. By understanding some basic compatibility concepts, builders and building owners can ensure their structures will perform as expected, for years to come.
