Which material is commonly used for sealant backer rods?

The use of foam for sealant backer rods is predominant due to its flexibility, compressibility, and lightweight properties. Foam backer rods create an effective bond with sealants while maintaining the shape of the sealant joint, which is essential for controlling the flow and depth of the sealant. The foam also acts as a moisture barrier, preventing the sealant from adhering to the bottom of the joint and ensuring that it can expand and contract without losing its adhesive properties.

Foam backer rods are readily available in various diameters, allowing them to fit snugly within different joint widths, which contributes to their effectiveness. The material is also resistant to chemical reactions with sealants, making it an ideal choice in construction and glazing applications.

Wood, plastic, and metal are less suitable for this purpose. Wood can absorb moisture and is subject to rot or deform. Plastic might not conform well to various joint shapes or provide adequate compression. Metal can corrode and doesn't provide the flexibility needed to accommodate movement in joints. Therefore, the attributes of foam make it the optimal choice for backer rods in glazing and other sealant applications.