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A Guide to Backer Rods

May 15, 2019

Backer rods are a useful tool for filling in cracks and joints in order to help control the caulking process. Since the caulking process can result in excessive waste, rods allow for the amount of caulking or sealant to be optimized for the task at hand. These rods are constructed from polyethylene foam, allowing it to be compatible with industry grade sealants and caulking products. Since there are numerous types of rods each with their own unique properties and purposes, here’s a guide on their different variations and intended uses.



Closed Cell

This variant is distinct due to its unique cell structure. Its cells are completely enclosed by its walls instead of being interconnected to other cells. As a result, the material will not absorb liquids, making it a suitable choice for areas with high amounts of water or dampness. Closed cell rods are great for glazing installations, window and door applications, partitions, and curtain wall joints.


Open Cell

Open cell backer rods are very easy to compress and handle. This variant allows for the sealant to cure from both sides instead of the typical outside to inside direction. Normally, sealants cure due to a reaction between evaporation or atmospheric moisture. Additionally, these rods work well even in extremely cold temperatures. Open cell rods are suitable for bridge construction, parking decks, and precast units and copings.



Some backer rods have a unique bi-cellular makeup, combining the best of both worlds. The bi-cellular variant offers high compressibility, but closed cells on its outer skin in order to resist water. Due to its unique properties, it’s best reserved for areas that have irregularities. Nevertheless, it’s an excellent all-around solution for almost any scenario.


Alcot Plastics is the number one manufacturer of polyethylene foam products. We are devoted to providing unrivaled products to meet all of our clients' exact specifications. For more details, visit our website and contact us today.