Definition - What does Backer Rod mean?
This is an equipment used in conjunction with sealants to seal off cracks, joints and gaps wider than a quarter inch. It is used by builders and contractors to fill joints in mostly tiles and floors; it is used as a substitute of caulking. It is made of polyurethane foam-based on the surrounding atmospheric conditions.
Corrosionpedia explains Backer Rod
This rope-like structure is inserted into the crack to fill a certain portion of the gap so that sealants or mortars can be applied for finishing. The two main backer rods are the closed cell foam rod and the open backer rod. They can be applied vertically or horizontally.
The open-celled rod is less dense and flexible; therefore, it can be compressed to fit well in gaps in an indoor environment. The closed celled rod on the other side has some hardness and increase in density. This is used for outdoor sealing and heavy duty tasks; it is preferable because it has some waterproofing effect when sealing concrete or walk paths.
In packaging, they appear with different sizes, governed by the diameter of the rods. These rods are cheaper since they are made of foam material. Since they are used together with the sealants, the baker rods act as a depth limit so that uniform seal is achieved. The rigidity of the backer rod is determined by the chemical and physical properties of the material.