When you think about your roof, shingles or metal panels might be the first thing that come to mind. But one critical aspect of your roofing system is the sealant. In this article, we’ll break down what roofing sealant is and explore the most common reasons it can fail in both residential roofing and commercial applications.
What Is Roofing Sealant?
Roofing sealant is a highly flexible material used to seal gaps, seams, and transitions in a roofing system. It creates a water-resistant barrier to help prevent leaks and protect structural integrity. You’ll typically find roofing sealant around vents, flashing, pipes, skylights, and other roof penetrations.
Its chemical makeup allows it to flex and move with the roof as materials expand and contract due to temperature changes. Common types of roofing sealant include silicone, polyurethane, butyl, acrylic, and bituminous sealants.
Many roofing sealants are designed to resist UV degradation and can adhere to a wide range of roofing materials. Sealants can be applied using a brush, trowel, or caulking gun, depending on the location and type.
Why Is Roofing Sealant Important?
Roofing sealant helps close off small gaps and seams where water could enter your roofing system. This minimizes the risk of leaks, water damage, and potential mold or mildew growth in the roof deck or attic space.
Sealant also helps limit minor air intrusion around penetrations, which can support better energy performance. While it is not a replacement for proper insulation, it does contribute to sealing areas that could otherwise compromise efficiency.
Sealant should be applied as part of every new roof installation or replacement when addressing flashing and transition areas. Properly installed sealant enhances the overall durability and weather resistance of the roofing system.
Common Causes of Failure
Understanding why roofing sealant fails can help you avoid unnecessary repairs or water damage. Here are the most common causes of premature sealant failure.
UV Radiation
Prolonged exposure to sunlight is one of the leading causes of roofing sealant failure. Over time, UV radiation breaks down the chemical structure, causing cracking, loss of adhesion, and chalking.
To avoid this, always choose a sealant that is specifically rated for UV resistance. Scheduling routine roof inspections and reapplying sealant as needed can help extend its effectiveness.
Thermal Expansion and Contraction
Roofing materials naturally expand and contract with temperature changes. If the sealant used doesn’t have enough flexibility, it can separate from flashing, seams, or joints, creating gaps where water can enter.
Using sealants rated for high joint movement, typically 25 percent or more, helps ensure they can flex with roofing materials without breaking their bond.
Poor Surface Prep
For best performance, roofing sealants must be applied to a clean, dry surface. Dirt, oil, or even a small amount of moisture can prevent bonding, leading to early failure and leaks. A professional roofer will clean and dry the surface before applying sealant to ensure long-term adhesion.
Incompatible Sealant
Not all sealants work with every roofing material. For example, some acrylic sealants are not ideal for metal roofing unless specifically formulated for that use. Using the wrong type of sealant can result in poor adhesion, shrinkage, bubbling, and failure.
Always ensure the sealant is compatible with both the material and environmental conditions on your roof.
Weathering
Climate plays a big role in how long roofing sealants last. Frequent rain, pollution, or freeze-thaw cycles can break sealants down faster. Signs of weathering include drying, hardening, or cracking.
Regular inspections and reapplication every five to ten years, or sooner in extreme climates, can prevent weather-related failure.
Improper Application
If sealant is applied too thin, it may not fully cover the joint or seam. If it’s applied too thick without proper tooling, air pockets can form. Both can cause premature failure.
The best way to ensure proper application is to rely on trained roofing professionals who follow manufacturer instructions and apply sealant with the right techniques.
Building Movement
Buildings naturally shift and settle over time. If the roof deck moves significantly, even flexible sealants may split or shear under the stress.
To reduce this risk, use a roofing sealant with a joint movement rating of at least 25 percent. This provides better durability in structures that are prone to settling or thermal movement.
Water Intrusion During Curing Process
Always check the weather before applying sealant. Exposure to rain, dew, or condensation during the 24–48 hour curing window can cause bubbling, weak adhesion, and eventual leaks.
To prevent this, avoid application during high humidity or rain-prone days.
Excessive Foot Traffic
In commercial settings, foot traffic is a common but often overlooked cause of sealant failure. Repeated walking near seams or penetrations can compress or crack the sealant.
Installing roof walk pads or designated walkways can help protect sealant in high-traffic areas and extend the life of your roofing system.
Reliable Roof Repair Service
KPost Company provides expert roof repair and sealant solutions throughout Dallas, TX. From leak repair to roof replacement and professional inspections, our team ensures long-lasting results. Contact us today to discuss sealant compatibility, maintenance schedules, and the best products for your roof.
