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Everything You Need to Know About Backer Rods

November 27, 2020

One of the most integral components of sealant joints is the backer rod. It provides key functions that enable the sealant joint to perform its work. First, the rod acts as a bond breaker which prevents what is called three-sided adhesion. This refers to when the sealant adheres to both sides of the joint and the bottom. The goal, therefore, of using a backer rod, is to bond the sealant only to the sides to prevent it from moving upon impact.


When there are joints between tiles or cement blocks, backer rods can fill up the vacant space.


The rods are placed in the grooves or cracks, before the space is filled up with mortar, adhesive sealants, or chinking. Backer rods strengthen the bond area while keeping the depth of sealant consistent in the middle section for potential movement without causing breakage to the bond.


Backer rods come in three major types, namely, closed cell, open cell, and hybrid. Each one of them has its own set of benefits and drawbacks, depending on your specific applications. The open cell rod can be easily compressed and is able to facilitate the cure of the sealant. However, it is not suitable for installations in flat or horizontal joints where water can cause moisture to seep into the underside of the sealant.


The closed-cell backer rod is the best option for flat joints because of its structure that can keep moisture from getting through. However, careful consideration is needed when installing this rod as it is quite challenging to compress into the joints. Once it gets punctured where the sealant sits atop, it can create a void that results in outgassing. This is where a hybrid backer rod becomes useful. It has an internal open cell structure that makes it easy to install and a closed-cell exterior that can be used on horizontal and flat joints without causing moisture to seep through it.