BackerRod

Backer rod is a flexible, cylindrical foam material used as a backing in joints that are to be sealed with sealant. It is typically made from polyethylene or polyurethane. The primary purpose of backer rod is to control the depth of the sealant. By inserting a backer rod into a joint, the installer can ensure the sealant achieves the correct width-to-depth ratio, which is crucial for its performance and longevity.

Proper sealant tooling relies on achieving this ratio. A joint that is too deep relative to its width can lead to the sealant cracking or failing prematurely. Backer rod, by filling the excess depth, prevents this. It also acts as a bond breaker at the bottom of the joint. This prevents the sealant from adhering to both sides of the joint and the backer rod, allowing the sealant to move more freely with the expansion and contraction of the joint.

Backer rod comes in various diameters to suit different joint sizes. It is generally available in closed-cell or open-cell foam. Closed-cell backer rod is less permeable to water and is often preferred for exterior applications or where moisture resistance is critical. Open-cell backer rod is more compressible and can absorb some moisture, making it suitable for interior applications where a tighter fit is needed. The installation involves compressing the backer rod slightly and pushing it into the joint to the desired depth, ensuring it is snug but not over-compressed.