Technical Advisory: Correct Application of Seam2Seam™ Sealant


Correct Application of Seam2Seam™ Sealant

GenFlex Seam2Seam Sealant is an essential component of Seam2Seam EPDM SA membrane roofing systems. Incorrect application of Seam2Seam Sealant may compromise seam integrity and will be noted on GenFlex inspection reports. Please refer to the guidelines below on proper application of Seam2Seam Sealant and implement best practices with roofing crews to ensure installations meet GenFlex requirements.

All Seam2Seam EPDM membrane seam overlaps require Seam2Seam Sealant over the seam edge, including field seams, T-Joints, flashing corners, and vertical/side laps. An acceptable GenFlex primer [1] is always required.

  • Surfaces must be clean, dry, and free of loose or foreign materials, oils, and grease. For this reason, sealant must be applied by the end of each working day.
  • Apply an acceptable GenFlex primer to the seam edge before installing Seam2Seam Sealant [2]. If a seam edge is contaminated, clean the seam a minimum of 1.0″ (25 mm) on each side of the step-off with GenFlex Cleaner and allow to dry before applying primer.
  • Apply a continuous bead of Seam2Seam Sealant approximately ¼” – ⅜” (6.3 mm – 9.5 mm), centered over the seam.
    • Keep the applicator tip centered over the seam edge. The sealant bead must contact the upper and lower parts of the step-off. Applying Seam2Seam Sealant above or below the step-off is not acceptable.
    • Do not tool, thin, or spread Seam2Seam Sealant.
    • A battery gun is required to ensure consistent, even application.
    • Regularly check for proper Seam2Seam Sealant application throughout the project and correct as needed.
    • When applied properly, one cartridge will cover 20′ – 22′ (6.1 – 6.7 m) of seam.

When inclement weather is expected, apply GenFlex primer to all seam edges before leaving the project. On the next working day, clean, prime, and seal all seams as described above.

Refer to GenFlex Seam2Seam EPDM Application Guide, Product Data Sheets, and installation details for additional information or contact Firestone Technical Services at (800) 443-4272.


[1] GenPrime, GenPrime LVOC, GenFlex Clear Primer, or GenFlex Clear LVOC Primer.

[2] Refer to GenFlex application instructions for proper application of GenFlex primers.


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