Sealant failures due to gassing, slow curing, or three-sided adhesion are costly call-backs. Ensure optimal sealant performance from the start. Adheseal Open Cell Backing Rod provides the critical non-gassing foundation that allows sealants to cure efficiently and perform as designed, preventing premature joint breakdown.

Why this product exists

This backing rod is engineered to eliminate common sealant application failures. Its open-cell polyurethane foam structure allows sealants to breathe and cure from both sides, significantly faster than with closed-cell alternatives. This breathability, combined with its non-gassing property, prevents internal bubbles and bond failures. It ensures consistent sealant depth, preventing three-sided adhesion that restricts joint movement and causes premature cracking. We developed this product to serve as a reliable bond breaker and depth control for cold-applied Acrylic, Silicone, PU, MS, SPUR, and Hybrid sealants, plus compatibility with all known hot-pour sealants, across diverse applications like expansion joints, window glazing, precast panels, and bridge construction.

The numbers that matter

  • Non-gassing, breathable open cell structure: Unlike typical closed-cell polyethylene foam backing rods, this open-cell design eliminates trapped air that can cause sealant gassing and promotes a faster, more uniform cure by allowing moisture vapour to escape from beneath the sealant.
  • Resilience and compression: Designed to be compressed by no less than 24% and no more than 75% of its original diameter when installed. This ensures the rod stays firmly in place, maintains the correct sealant depth, and provides a reliable bond-breaking surface without over-compressing.
  • Wide service temperature range: Withstands continuous service from -60°C up to intermittent temperatures of 260°C. This broad range ensures stability and compatibility in various climates and with different sealant types, including specialist hot-pour applications, provided the sealant application temperature itself does not exceed 70°C.
  • Conforms to irregular joints: The polyurethane foam offers >90% elongation and excellent compressibility. This allows a single rod size to accommodate a wider range of joint widths and shapes, reducing the need for multiple stock sizes and simplifying installation in variable joints.

What it's like to use

Install this backing rod into a clean, prepared joint, taking care not to entrap air. The foam should be compressed approximately 25% larger than the joint width to ensure a snug fit that stays in place. Use the Adheseal Backing Rod Insertion Tool to achieve consistent depth without stretching the rod longitudinally. This maintains the specified 2:1 width-to-depth ratio for your sealant, crucial for optimal performance. Once inserted, the backing rod's low surface strength ensures that dynamic movement in the sealant will not be adversely affected by adhesion to the rod.

Where this product excels

  • Expansion joints in precast concrete: Provides crucial depth control and a non-adhering surface for movement joints in large concrete panels, ensuring the sealant performs across seasonal expansion and contraction cycles.
  • Window glazing and frames: Creates a uniform sealant bed in window installations, preventing sealant extrusion and facilitating proper adhesion to glass and frame materials.
  • Bridge construction and heavy civil works: Supports high-performance sealants in large-scale infrastructure, accommodating significant structural movement without compromising sealant integrity.
  • General movement joints in various building elements: Ideal for controlling sealant depth and preventing three-sided adhesion in diverse applications, including masonry, brick, timber, and painted surfaces where long-term sealant flexibility is paramount.

How it fits in a real system

This backing rod typically serves as a foundational component in multi-stage joint sealant systems. In critical joint sealing applications, you install it after priming the joint with a product like Adheseal 2001 primer, but before the application of the main sealant. Its role is to define the sealant's bond area and depth, which is essential for the sealant to achieve its specified movement capability and longevity. This sequencing ensures that the sealant cures correctly and is properly supported against tensile and compressive forces.

Choose this when

  • When you need to prevent three-sided adhesion in sealant joints to allow for maximum movement.
  • When specifying for cold-applied Acrylic, Silicone, PU, MS, SPUR, or Hybrid sealants where a breathable, non-gassing backing rod is essential for proper cure.
  • When dealing with irregular joint shapes or widths that benefit from a compressible, conformable backing material.
  • When sealant joint design requires a precise 2:1 width-to-depth ratio, easily achieved by selecting the correct rod diameter.

Don't use this when

  • Not for: Applications where the sealant is heated and applied at temperatures exceeding 70°C, as the rod's performance in these conditions is not guaranteed without specific consultation.
  • Not for: Internal swimming pool applications or areas exposed to high levels of chlorine (above 5ppm), as these conditions can compromise the rod's integrity.
  • Not for: Permanent UV exposure, as prolonged direct sunlight can degrade the polyurethane foam over time.
  • Not for: Installations requiring excessive longitudinal stretching of the rod, as this can alter its density and compromise its intended function.