Why Silicone Beats Polyurethane for Exterior Joint Sealing
For decades, polyurethane sealants were the default for exterior joints in construction. They were cheap, they worked, and most importantly, they were everywhere. But if you’ve worked in the field long enough, you’ve probably seen their downside too: cracking, yellowing, shrinking, or worse, complete joint failure a few years down the line.
So what changed?
The construction industry got smarter. Standards got tighter. And a new generation of builders started asking better questions: What lasts longer? What handles UV better? What actually performs under stress? And time after time, the answer is silicone.
Why Polyurethane Had Its Moment
Let’s give credit where it’s due. Polyurethane sealants made sense for a long time. They were easy to apply, relatively inexpensive, and stuck well to porous surfaces like concrete and masonry. For fast-moving builds with tight budgets, they checked all the boxes.
But polyurethane’s performance has a shelf life, literally and figuratively. Many products degrade quickly when exposed to sunlight and moisture. They can harden, discolor, lose flexibility, and eventually detach from the substrate altogether. These aren’t hypothetical risks; they’re field-tested truths.
As building owners and contractors began prioritizing total lifecycle cost over initial material price, the shortcomings of polyurethane became impossible to ignore.
Silicone Changed the Game
Silicone sealants brought a new level of durability and resilience to the job site. Unlike polyurethanes, silicones are inherently UV stable, which means they don’t chalk, crack, or yellow when exposed to sunlight. They’re also hydrophobic, meaning they don’t absorb moisture, an essential trait for exterior joints that are constantly exposed to the elements.
But the biggest advantage? Long-term elasticity.
Silicones remain flexible over decades, not just years. That flexibility is critical in dynamic joints, areas subject to expansion, contraction, and structural movement. Whether it’s curtain walls, window perimeters, or control joints in concrete, silicones like MF889 and MF896 from Deerco maintain their adhesion and performance without going brittle or pulling away from the joint.
Real-World Payoff: Fewer Failures, Lower Cost Over Time
If you’re a GC or procurement lead comparing material costs, silicone may look like the more expensive option at first. But that’s the wrong metric. The real question is: What’s the cost of failure?
When a polyurethane sealant fails, you’re not just buying a new tube. You’re tearing out failed joints, grinding out residue, reapplying under less-than-ideal conditions, and absorbing the labor hit. Not to mention the callbacks, the lost client trust, or the risk of water intrusion and mold behind walls.
Silicone doesn’t just perform better, it lasts longer, requires fewer repairs, and reduces lifecycle cost dramatically. That’s why more architects, owners, and specifiers are making the switch.
Silicone Is More Than Weatherproofing
While many still think of silicone as just a weather sealant, high-performance formulations like MF899 are proving that silicone can also deliver structural strength, adhesion to complex substrates, and compatibility with modern cladding systems. This is especially critical in high-rise and mixed-material construction where aesthetics and performance are non-negotiable.
Silicone sealants are also non-staining, making them ideal for use on natural stone and architectural finishes, something polyurethane often fails at. Products like MF889A, designed for stone joints, prevent the unsightly blotching and oil migration that can ruin an expensive façade.
The Bottom Line: Silicone Wins Where It Counts
This isn’t about marketing. It’s about the job site. It’s about the places where building materials either hold up, or fall apart. When you specify silicone, you’re making a decision based on long-term value, field-tested reliability, and code-compliant performance.
At Deerco, our silicone lineup is designed with these realities in mind:
MF889, Long-lasting weatherproofing performance
MF889A, Non-staining formula for natural stone
MF896 / MF896L, Designed for both vertical and horizontal concrete joints
MF899, Structural-grade silicone for glazing and high-performance façades
So the next time you’re evaluating joint sealants, ask yourself: Are you building for this year, or for the next 30?
If it’s the latter, silicone isn’t just a better option. It’s the only one that makes sense.
