Frost King C23CP Poly Foam Backer Rod

Product Description

The FROST KING C23CP is a polyethylene foam backer rod designed to back-fill joints and gaps before applying caulk or sealant. It creates a firm, compressible base that controls sealant depth, promotes the correct two-point adhesion profile, and prevents three-sided adhesion that would cause premature sealant failure. This component is a standard part of proper weatherization and sealing work in both residential and light commercial applications. HVAC technicians, plumbers, general contractors, and weatherization specialists use backer rod as part of air-sealing and joint-prep workflows. It is sold as a single unit.

Backer rod is used wherever a gap or joint needs to be sealed with caulk or sealant and the depth of that joint exceeds the recommended sealant depth. Typical applications include expansion joints, window and door rough openings, penetrations through walls or floors, and HVAC duct connections at framed openings. It is appropriate for interior and exterior use wherever compatible sealants are being applied over compressible foam.

Key Features

• Polyethylene foam construction provides consistent compression and recovery in joints
• Controls sealant depth to prevent over-application and wasted material
• Promotes two-point adhesion, reducing the risk of sealant cracking or delamination
• Compatible with most common caulks and sealants used in construction and HVAC work
• Lightweight and easy to cut to length on the job

Compatibility

Designed as a general-purpose backer rod for use with standard caulk and sealant applications in residential and light commercial construction, weatherization, and mechanical systems work.

Installation Notes

Install backer rod by pressing it firmly into the joint or gap to the correct depth before applying sealant. The rod diameter should be slightly larger than the joint width to ensure a snug friction fit. No adhesives or fasteners are required. Follow sealant manufacturer guidelines for joint depth-to-width ratios and confirm the backer rod material is compatible with the sealant being used.