Backer Rod

A rod-shaped foam material (typically closed cell polyethylene) that is installed under compression in a joint. Sealant is applied over the backer rod. The backer rod provides a backing, controls sealant joint depth, acts as a bond breaker to prevent three-sided sealant adhesion, and provides an hour-glass contour for the finished sealant bead.

Related terms: Joint, Sealant, Bond Breaker, Info-406: Air Sealing Windows