Used in the construction of homes, sidewalks and masonry, backer rod, also known as expansion joint filler, increases the performance of every application it is used in. Because of changes in ground angle, weight distribution, weather and its relative inflexibility, concrete is often divided into tiles or sections to cover an entire area. Between these tiles are small crevasses or joints that allow room for the concrete to contract, expand, shift and settle. Left open and uncovered however, moisture will get into the concrete movement joints and slowly fracture and damage the structure. The answer to this is to fill the joint with flexible, waterproof sealant. This is where expansion joint foam steps in. Backer rod is a strip of foam, often cylindrical, that is inserted between joints before caulk or sealant is applied. The inclusion of expansion joint filler material does not allow sealant to form a three-point bond to the slabs and base surface, maintaining flexibility and preventing damage to the substrate. Foam Factory, Inc. stocks this essential building material in a variety of diameters and roll lengths for completing any project, large or small.