Types of Backer Rods and thier Necessity in Construction

A backer rod is necessary in filling gaps between construction surfaces before caulk is applied to completely seal the joint. Most contractors use it in flooring and tiling while a few use it in surface counters, window sealing and wall paneling to achieve a perfect surface finish. There are two main kinds of backer rod ; the open cell and closed cell. Open cell rods are appropriate for indoor applications where the moisture content is low. The closed types are most appropriate for outdoor environments where waterproofing and insulation is needed. The two types of rods are necessary in achieving good appearance, firmness and durability.

The open cell backer rod is made of airy breathable material which is slightly denser than that used in the closed type. The airy nature makes it easier to install due to its softness and flexibility. In cases where the size of the gap varies, the open cell rod can be compressed to fit perfectly into the narrower sections. This makes it more universal than the closed type.

The closed cell rods are firmer and harder to bend as compared to the open cell versions. This makes them harder to install due to their rigidity. However, they are most appropriate for outdoor application where the conditions are harsh.  They are able to repel moisture and provide a stable finishing to the opening.

The type of backer rod used by a builder depends on the specific conditions of the installation site as well as the size of gap to be filled. Small joints ranging between ¼ - 3/8 inches are sealed and insulated using the closed cell type while larger indoor joints are filled with the open cell versions. Backing rods give the building materials a bending and expansion allowance depending on the environmental conditions they are exposed to. Therefore, the sealants used should also be flexible throughout the life span to stand the movements, bending and expansion experienced by building materials.