Soft (Open-Cell) Backer Rod

Soft open-cell backer rod is a flexible polyurethane foam joint backing for sealant joints that are irregular or vary in width. It compresses easily to conform to uneven joint profiles, controls sealant depth and acts as a bond breaker so the sealant can move freely with the joint.

Key Features

• Highly compressible – conforms to irregular and variable-width joints
• Breathable open-cell structure lets sealant cure from the back as well as the face
• Can be cut or punctured without outgassing
• Bond breaker prevents three-sided adhesion
• Controls sealant depth and reduces material waste

Typical Applications

• Vertical expansion and control joints in masonry, concrete and precast
• Window, door and cladding perimeter joints
• Above-grade building envelope joints with uneven edges

Sizes & Packaging

Joint widths are approximate, based on the standard practice of sizing backer rod about 25% larger than the joint width. Not recommended for horizontal, below-grade or water-immersed joints, where open-cell foam can absorb water – use closed-cell backer rod instead.

Installation Notes

• Clean and dry the joint before installation.
• Size the rod about 25% larger than the joint so it stays in place under compression.
• Insert with a blunt tool for a consistent depth.
• Set depth to the sealant manufacturer’s recommended width-to-depth ratio (typically about 2:1).
• Do not stretch or twist the rod during installation.
• Follow the sealant manufacturer’s installation guidelines and confirm compatibility.