4 in. Backer Rod, Closed Cell (6 Ft) - 4 INCH DIAMETER POLY BACKER ROD, CLOSED CELL, NON-STICK SKIN, 6-FOOT LENGTH/PIECE. PRICE/PIECE. (color is generally white but could be gray, white or charcoal and is not selectable; 8 pieces/carton).
4 in. Backer Rod, Closed Cell (6 Ft)
$20.00 SALE $15.95
(Savings: $4.05)
 Buy 8 or more and pay $14.00 each (save 30.0%) 
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4 inch Diameter Poly Backer Rod, Closed Cell, Non-Stick Skin, 6-Foot Length/ Piece. Price/Piece.


  • 8 Pieces/Carton. Order full cartons for discounts.
  • Color could be white, gray or charcoal and is not selectable.


Round, resilient, polyethylene extruded closed celled foam with a water resistant outer skin. Provides controlled depth for sealants. Compresses up to 50 percent in smaller sizes and 30 percent in large sizes. Does not stick to sealants. Exceeds ASTM standards for bond breakering materials. No bond breaker is required. Very high moisture resistance. Will not absorb ground water. Compatible with all know types of sealants including butyl, polyurethane, silicones, tri-polyimer, polysulfide, acrylic, etc.

Color could be white, gray or charcoal and is NOT SELECTABLE.

Carton Packing: 8 pieces/carton, 14 lbs, 17 x 10.3 x 74 inch size


  • High moisture environments
  • Ground based expansion joints
  • General purpose sealant backing
  • Use together with self-leveling sealant
  • Highway joints
  • Parking garages
  • Around perimeters of door and window frames
  • Coping and glazing joints
  • Log Home chinking
  • Isolation joints


Select a backer-rod diameter that is approximately 25% larger than the width of the joint.

Joint Width  Recommended Diameter
3/16" - 1/4"       3/8"
3/8" - 1/2"         5/8"
1/2" - 3/4"         7/8"
3/4" - 7/8"      1-1/8"
7/8" - 1-1/4"   1-1/2"
1-1/4" - 1-1/2"   2"
2" - 2-1/2"         3"
2-1/2" - 3-1/4"   4"


1. Joint fillers have three major functions:

  • Controls depth of the sealant in proper relation to joint width.
  • Provides backing against which the sealant is applied, forcing the sealant to the sides of the joint.
  • Prevents 3-sided bonding, ensuring proper function of sealant.
  • 2. To install, compress backer-rod into the joint before sealants are applied. Joint or opening should be clean and dry and free of obstructions. Install backer-rod using a blunt probe or a plain faced roller to force the rod to the desired depth.

    3. Compress to a depth of about 1/2 of the width measured at the crown of the backer rod.

    4. A template or roller gauge may be used to control the depth at which the rod is placed.

    5. Do not stretch, puncture or tear backer-rod during installation but gently force into the joint so that the backer-rod fits tight against the sides of the joint.


    1. Follow suggestions for joint-sealant application as directed by sealant manufacturer.

    2. Where priming of the joint is necessary, primer should be applied only to the joint surfaces and allowed to dry before Backer-Rod is placed. DO NOT prime Backer-Rod.


    Email us at sales@bestmaterials.com or
    Call us at 1-800-474-7570 or 602-272-8128
    You'll get a prompt reply!

    similar product terms: backer rod, soft celled backer rod, chinking, chink backing, caulk backing, sealant backing, sealant support, caulk support, soft cell foam, closed cell foam rod, log home chinking

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