Backer Rod
Flexible foam rope pressed into joints before sealant application to control sealant depth and prevent three-sided adhesion.
In Detail
Backer rod (typically closed-cell polyethylene foam) is installed in joints wider than 1/2" to limit sealant depth to 50% of joint width. This ensures the sealant adheres only to the two opposing faces (two-sided adhesion), allowing the sealant to stretch and compress without tearing.
Related Materials
Polyurethane Sealant
Flexible, paintable sealant for exterior joints that move. Superior adhesion to concrete, masonry, and wood. Excellent UV and weather resistance.
Silicone Caulk
Permanently flexible, 100% waterproof sealant. Resists mold and mildew. Not paintable. Best for wet areas and non-porous surfaces.