Joint Filler and Sealant Backing Materials


Sealant backing and bond breakers establish sealant depth and prevent detrimental three sided adhesion. Properly installed sealant backing prevents sealant leakage and creates a proper sealant profile.  Sealant backing function ceases once sealant is applied, tooled, and cured.

  • A joint filler is inserted into joints that are deeper than required for the sealant backing and sealant installation.
  • For moving joints the joint filler and sealant backing must be compressible.
  • Sealant backing provides resistance to sealant tooling pressure and helps to attain proper wetting of the substrate when sealant is tooled.
Recommended Backing Materials
  • Closed cell sealant backing:  primarily a polyethylene foam with a surface skin.
    • Vertical and horizontal joints with one or two component sealants.  Approved for use in EIFS applications.
    • Closed cell sealant backing must be no more than 25%-33% larger than joint width so it remains in compression and in place during sealant installation.
    • Do not rupture the skin of closed cell sealant backing material during installation, this can cause air bubbles in the sealant compromising its ability to perform.
  • Open cell sealant backing: primarily a urethane foam without a skin.
    • Vertical joints utilizing one-component sealants when cure speed is critical.
    • Double caulk beads in vertical joints for curing of initial (internal) caulk bead.
    • Must be at least 25% larger than joint width so it remains in compression and in place during sealant installation. Not for use in horizontal traffic joints or EIFS applications.
  • Bi-cellular sealant backing: composed of both open and closed cell polyethylene or polyolefin foam with a surface skin. Recommended for all sealant applications with the exception of applications requiring rapid curing from backside.
  • Bond breaker tape: primarily a self-adhesive polyethylene or teflon material.

Not Recommended for Backing Material

  • A rigid joint filler or sealant backing in joints that will experience movement.
  • Using braided sealant backing to compensate for a joint opening that is too large for the backing material.

 

Recommended Backing Materials

  • Closed cell sealant backing: primarily a polyethylene foam with a surface skin.
    • Vertical and horizontal joints with one or two component sealants. Approved for use in EIFS applications.
    • Closed cell sealant backing must be nomore than 25%-33% larger than joint width so it remains in compression and in place during sealant installation.
    • Do not rupture the skin of closed cell sealant backing material during installation, this can cause air bubbles in the sealant compromising its ability to perform.

 

  • Open cell sealant backing: primarily a urethane foam without a skin.
    • Vertical joints utilizing one-component sealants when cure speed is critical.
    • Double caulk beads in vertical joints for curing of initial (internal) caulk bead.
    • Must be at least 25% larger than joint width so it remains in compression and in place during sealant installation. Not for use in horizontal traffic joints or EIFS applications.

Refer to Pecora Technical Bulletin #106 Backer Rod Use for more information. 

 

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