Art House Mark Ham

If you’ve ever walked along an even, smooth sidewalk, or kicked back in a toasty log cabin during a blizzard, you owe a debt of gratitude to a product you’ve likely never seen. That product is foam backer rod; an incredibly important building material in masonry and construction that gives structures durability, flexibility, and longevity.

 

Backer rod, also known as expansion joint filler, is a thin waterproof foam cylinder that is packed into the joints between poured concrete, logs in cabin construction, and cracks or fractures in the repair of similar building materials. Its role as a bond breaker between substrate base surfaces and the waterproof sealant applied to the joint is vital, because if caulk completely fills the joint, a three-point bond is formed. If this happens, due to the expansion and contraction during seasons and temperature changes, the adhesive will pull against the two materials it is sealing and the substrate, causing damage or failure when it tears away from one. It also is important to fill these joints for the purpose of keeping joints free of moisture. Cover foam and sealant protects against the damage and degradation of building materials during freeze cycles. If a joint between two slabs in a sidewalk remains unsealed and fills with moisture and freezes, the expansion of water into ice can crack the cement.

 

Caulk and sealant do not bond to the foam backer rod which is packed in tight enough to expand with materials. Keeping that space filled allows the sealant to stretch and compress, much like a rubber band. Filling the majority of the crack’s space with foam is also much more cost-effective than doing the same with caulk, making backer rod a cost-saving measure as well, in addition to its structure-saving benefits.