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Distinguishing Various Types of Backer Rods

January 06, 2021


Backer rods are an essential part of any sealant joints because they are the ones that fill the gaps between two building materials. Utilizing them brings many advantages because of the three major functions they perform. These foam rods act as a bond breaker to avoid the notorious three-sided adhesion wherein sealant adheres to the bottom and both sides of the joint. They provide support by enabling the sealant to be pushed to the bond line, ensuring its wet-out to the substrate surface.


They also promote an hourglass shape which optimizes the bond area while keeping the depth of the sealant consistent.


There are three different varieties of backer rods. Commonly designed as fillers for joints, they can also be utilized for purposes such as flooring, paneling, tiling, and so on. They come in standard diameter sizes that range from a quarter inch thickness to 4 inches. These rods also come in three types of foam – open cell, closed cell, and hybrid. Each type of foam provides a different characteristic in terms of versatility and resistance to moisture. Depending on your application, the type of foam used will vary.


The open cell rod is the easiest one to install because it is very pliable and can be easily compressed into gaps. It also facilitates the sealant curing of both sides. However, this type of rod is not recommended to use in flat or horizontal joints and in outdoor applications. This is because open-cell foam can’t repel water and are not a good insulator. On the other hand,  a rod made of closed cell foam is perfect to use outdoors and in heavy-duty applications because they are firmer and denser. They can repel moisture and provides higher insulation value. Finally, the hybrid type features an internal open-cell structure but a closed exterior. It is ideal for installation in flat or horizontal works since they won’t wick water through.


To learn more about backer rods and other products at Alcot Plastics, contact us today!