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Polyethylene foam closed cell backing rod:  

Polyethylene foam closed cell Backing Rod  


The Backing Rod is manufactured from extruded, closed cell polyethylene foam, available in rods with different diameters and lengths.  


The Backing Rod is used as a back up material for cold applied joint sealants to give the sealant the correct thickness. It also acts as a bond breaker, permitting the most efficient joint design.  


  • Provide firm backing for joints subject to hydrostatic pressure
  • Easy to apply 
  • Closed cell
  • No bond to most sealants
  • Compatible with cold applied sealants (polyurethane, silicone)
  • Different rod diameters
  • Good water resistance
  • Odourless  

Technical Data

  • Type: Extruded Closed Cell Polyethylene Foam
  • Colour: White
  • Chemical Resistance: Good resistance to oil, petrol and solvents.
  • Temperature Resistance: -40oC to +70oC
  • Storage: Store in dry conditions and protect from heat.                    


Diameter (mm)

Coil/Length (metre)




















When installing Backing Rod, be careful not to cut or puncture the surface skin. Care must be taken when bending the closed cell backing rod to avoid aggressive angles such as 90 degree, a rounded bend would be more suitable. During installation avoid excessive longitudinal stretching of the rod. Do not use as a backer, where sealant is heated and applied at a temperature above +70 oC. Rod diameter should be approximately 25% larger than the joint width.  

It should always be installed into a joint under compression to ensure that applying the joint sealant will not displace the foam. This is achieved by compressing Backing rod by 25% when installing into a joint (or by using foam 1/3 larger than the joint size). As a guide, use sizes noted on the chart below:

Diameter selection guide:  

Joint width

Diameter (mm)

4 to 5mm


6 to 8mm


9 to 11mm


12 to 13mm


14 to 17mm


18 to 20mm


21 to 27mm


28 to 35mm


36 to 45mm


Sealant depth must be a minimum of 6 mm at the thinnest section of the sealant bead, with a minimum bonding depth at the joint face of 6 mm on smooth glass and metal surfaces, and 12 mm on porous or rough surfaces. For larger joints, the depth of the joint face should normally be half the joint width.  

Application Instructions  

Application When used as an expansion or isolation joint filler, Backing rod should be positioned to provide for a surface sealing slot of required dimensions, ensuring that the sealing slot is free from mortar droppings, slurry, etc. When used as a backing strip, Backing rod is simply push fitted back into the joint. The cord diameter used should be 20 to 30% greater than the joint width. The circular section of Backing rod provides a convex face to ensure that applied elastomeric sealants are given optimum shape for minimum strain as the joint moves. Do not use sharp objects when fitting Backing rod, as any damage to joint backing may allow air voids to be formed in sealant.  

Roads, bridges, roof joints Backing rod is used as a backing strip for non traffic bearing expansion joints.  

External walling and cladding

Backing rod is used as a backing strip for expansion joints, as a gap filler for any open joints prior to application of any cold applied joint sealant and as a readily compressible, low load transfer joint filler in joints surrounding brick infill panel walling  


Backing rod is used as a gap filler and backing strip to support perimeter sealing around frames and sub-frames  

Internal finishes

Backing rod is used as a gap filler and backing strip to provide support to sealants in partition joints and around work tops, baths and other internal finishes and fittings  


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