Backer Rod (Closed-Cell)

closed cell backer rod(small).jpg
closed cell backer rod(small).jpg

Backer Rod (Closed-Cell)


Closed cell Backer rod, also known as backing rod is a closed-cell foam rod used to fill expansion joints. Backer rod supports the caulking compound (joint sealant) as it dries on top, and also provides additional expansion capabilities.

Closed Cell Backer rod is popular in applications where the joint is required to be watertight and non-breathable. It is a non-gassing foam, meaning the joint sealant will not bubble from air pockets forming after being applied.

It is commonly used in joints on concrete floor slabs, and occasionally between pre-cast panels. In terms of choosing the correct backer rod, select a size which is slightly larger than the joint width – to ensure a secure fit.

Use As a bond breaker/joint profile former to support elastomeric sealants in expansion joints between all common building materials.


  • Compatible with all elastomeric sealants.

  • Readily compressible.

  • Low load transfer.

  • Non gassing.

  • No water absorption.

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