Closed-cell polyethylene joint filler, back-up strips and cord.


Expandafoam is a closed-cell polyethylene joint filler for use as an expansion joint filler in brick and blockwork, isolation joints and hinge joints where a readily compressible low load transfer joint filler is required. Strip and cord sections are also available.

These are used as back-up strips for elastomeric sealants.


  • Back-up / bond breaker strip to support sealants

  • Bridge decks, abutments, pier hinge joints

  • Brick and blockwork in building superstructures


  • Readily compressible

  • Low load transfer

  • Excellent recovery after compression

  • Non-absorbent

  • Rot-proof

  • CFC-free

Specification clauses

The joint filler / back-up strips as detailed shall be Expandafoam supplied by Fosroc. Whether in sheet form or in strip or cord form, Expandafoam shall be installed strictly in accordance with the relevant Fosroc technical data sheet.

Application instructions - Joint sealing slots

When used as an expansion or isolation joint filler in brickwork, Expandafoam should be positioned to provide for a surface sealing slot of the required dimensions ensuring that the sealing slot is free from mortar droppings or slurry bridging.

Expandafoam sheets may be fixed into position using a suitable adhesive. Care should be taken not to contaminate the surfaces of the sealing slot with adhesive. Where Expandafoam is used as the joint filler no additional bond breaker is necessary. Used as a back-up / bond breaker strip Expandafoam serves both to regulate the depth of the sealing slot required and ensures that the movement of the joint sealant is not restricted by three-sided adhesion.
The size of the back-up strip should be approximately 20% greater than the joint width and depressed sufficiently to provide the required sealing slot dimensions. Circular cord sections provide a convex face giving an optimum seal configuration, they also overcome any problem of twisting which can occur with square or rectangular sections.

Product Enquiry - Expandafoam

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