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Estop Backer Rod

Circular Cord Polyethylene Foam

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Estop Backer Rod is a compressible closed cell polyethylene foam, supplied in circular cords lengths as a backup material for joint sealants.

Due to its light weight, it acts as debonding ‘tape’ between joint filler and sealant.


Estop Backer Rod performs several functions. They enable the correct width to depth ratio of the sealing slot to be obtained and provide a firm backing to ensure that sealants are forced against the sides of the joint during application. They function as a bond breaker at the back of the seal preventing additional stress on the sealant during joint movement.


  • Economical
  • Easy to install
  • Readily compressible
  • Rot-proof and non-absorbent
  • Provides bond breaker and minimum strain shape for joint sealant.

Design Criteria

Below is an example of a sealed expansion joint.

Estop Backer Rod Design Criteria

  • Estoliastic / Estojoint sealant
  • Estop Backer rod

Physical Properties

Form Compressible close cell foam circular cords
Storage life Indefinite
Water absorption Negligible
Colour Grey
Temperature stability, °C -40 to 60
Density, kg/m³ 35 to 40

Installation Instructions

Estop Backer Rod is selected oversize and push fitted into the joint. A blunt tool should be used to prevent damage to the surface skin of the cord during insertion.

The diameter of the cord should be approximately 20% to 25% larger than the width of the joint, positioned so that the required minimum sealant depth is obtained, measured at the centre of the joint.

When installed the circular section of Estop Backer Rod cords provides a convex face giving a near optimum minimum strain shape for elastomeric sealants reducing the build up of stress at the bond interface.

Packing & size

Estop Backer Rod is sold per carton. The length of each cord size contained in one carton is shown below.

Cord diameter (mm) Linear metres per carton
10 1150
15 550
20 350
25 200
30 160
40 270
50 180

Technical Support

Estop offers a technical support package to specifiers, end-users and contractors, as well as on site technical assistance.


Store in dry and covered condition.


There is no known health hazards associated with Estop Backer Rod in normal usage.

Additional Information

Estop manufactures and offers a wide range of complementary products, which includes waterstops, waterproofing products, grouts, anchors, specialized flooring products. In addition, a wide range of products formulated for repair and refurbishment of spalled concrete are available.