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Holes in your roof must be sealed, but externally applied caulking and sealants eventually dry out and crack, causing leakage and corrosion. Mounting solar panels, HVAC, snow guards, satellite dishes, and other accessories involves penetrating through EF roofs, so the sealants you use are critical to prevent roof leaks. Let’s explore how selecting EPDM and butyl sealants in the right applications will protect your roof.

Poor and messy externally applied caulking and sealant on an exposed-fastened metal roof

What Makes EPDM and Butyl Sealants So Effective?

Here’s a quick rundown of their features:

  • EPDM (ethylene propylene diene monomer) is a smooth, semi-hard, synthetic rubber that has high-tensile strength, flexibility, long lifespan, reliability in hot and cold climates and moisture resistance. EPDM is so waterproof; it’s even used as pond liners.
  • Butyl tape sealant (a copolymer of isobutylene with isoprene) is an airtight, watertight adherent rubber establishing an impervious moisture barrier. Uncured and sticky, butyl remains flexible even in extreme temperatures. One study shows butyl tape is still elastic and pliable after 33 years, and it’s estimated to last 60+ years.

Excellent elasticity demonstrated by the butyl sealant on a Denver, Colo. metal roof after 33 years in service.

How Can You Extend the Lifespan of EPDM and Butyl Tape Sealant?

As is true for almost anything, specific formulations of these sealant types differ from one manufacturer to another. Their individual formulations are proprietary and create their own “secret sauce.” In other words, they don’t all necessarily perform the same. This makes it imperative to source from a vendor who has a long history of success.

Beyond choosing a vendor with known integrity, the life of both EPDM and butyl tape can be extended in two ways to ensure their best performance over time:

  • Don’t use any sealant as a surface-applied fix on a roof. Sealant chemistry is complicated. If sealants aren’t properly protected, multiple factors can break down their chemical bonds. Surface applications are subject to degradation from UV, ozone, mechanical abrasion, dirt and other contamination. Application as a gasket material will help protect sealants from these threats. But even when applied as a gasket material, the best sealants can still have vulnerabilities. Look for attachments where the sealant is concealed from exposure and even protected at its edges if possible.
  • Avoid over-compression. Tighter is not better in this case. When you drive in the screw, seat it, but don’t over-torque it. Otherwise, you could thin and displace the gasket material, reducing its life and effectiveness. The best practice is to utilize a part design featuring a built-in-like “reservoir” to encapsulate the material and help prevent over-compression.

Where Is the Best Place to Use EPDM vs. Butyl When Mounting Your Attachments?

Geographic locations or “roof culture” affect mounting preferences. Attaching into the flat of the panel (the low valley of your corrugation or flat area between trapezoidal ribs) is commonplace in the U.S. In other roof cultures, the penetration is in the higher point of the profile, away from the drainage plane (into the rib).

“Top-fix” – EPDM is a top choice when attaching in the high (into the rib)

Because EPDM is semi-hard (like gasket material), it needs to attach to a flat, even surface to create a watertight connection. The smooth rib of your EF roof profile is a perfect match for EPDM.

“Bottom-Fix” – When mounting in the low (valley), butyl sealant is ideal.

Butyl’s flexible nature allows it to conform to the irregular surfaces (minor ribs and striations) in the panel valley. By using butyl tape, the sticky sealant retains its shape for a mess-free application. When mounting in the low, use only products designed to attach through the roof sheet into the structure or deck – never to the sheet only – in order to ensure stability, weathertightness and roof protection.

EPDM and butyl are top sealants on the market. Here’s a recap:

  • Use products with factory-applied sealants.
  • Select parts designed to protect sealants from over-compression, UV and environmental contamination.
  • Use EPDM when attaching into the high of the rib and butyl in the low.

Learn more how to leverage EPDM and butyl sealants to avoid roof leaks and protect the life of your EF roof.

Sponsored Content by S-5!



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