Photo Source: Summerhill

Foam backer rods are a common gap filler that an insulator may need to use on site. These rods can be used to fill large cavities or gaps around windows, doors and foundations, prior to sealing the area with an expanding foam product. They also serve to prevent expanding foam from falling into the cavity and restricting the pressure equalization cavity.

Foam backer rod (closed-cell compressible foam rope):

• Excellent for filling gaps before caulking
• Ensure caulking will fill the gap (see product specifications for maximum joint width)
• Available in diameters of 6 to 50 mm (1/4 to 2in.)