Butyl Flashing-Grade 321 is a single-component, trowel-grade, seam sealer specifically formulated to provide a water-tight, weather-resistant membrane with excellent permeability and UV protection. Butyl Flashing-Grade 321 offers good elongation and tensile strength to resist lateral movement and allow for natural daily expansion and contraction of the roofing substrate.

  • Ideal for sealing holes, cracks and joints
  • Highly flexible
  • Superior elongation and tensile strength
  • Excellent elongation and tensile strength
  • Reduces daily expansion and contraction (thermal cycling) of roofing substrate

Butyl Flashing-Grade 321 is recommended as a protective vapor barrier seam sealer for a variety of situations, including all types of seams, fasteners, gaps between metal panels, gutters, vent pipe flashings, air conditioning units and expansion joints. Ideal for metal roof applications with visible rust and all types of flat roofing substrates.

  • Metal
  • Modified Bitumen
  • Single-ply
  • Smooth BUR
  • 5-gallon pail
  • 2.5-gallon pail
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