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What are the Different Options for a Backer Rod?

May 05, 2021

Backer rods can take the form of round and flexible lengths of foam. They act as a backing in joints or cracks in order to assist with controlling the amount of sealant used. A backer rod also functions as a back stop. For the purposes of achieving an optimal fit, numerous sizes/diameters are created to match the size of the joint being sealed. Apart from shape, it is important to consider the different versions of foam cell structures that exist: closed cell, open cell, and bi-cellular. Each option makes a crucial difference surrounding irregular joint application, the desired flexibility within the joint, and the chosen sealant.

Alcot Plastics Ltd. fulfills the backer rod needs of our clients, and can supply a variety of other products for business or personal use.

Closed Cell

This type of foam is recognized based on the cells, which are completely enclosed by its walls and do not interconnect with other cells. Based on the properties of this material, it will not wick moisture, allowing it to be suitable for joints where water or dampness can build up. Sealants for example will have an easier time sticking to closed cell backer rods because of their bonding surface area.

Open Cell

Backer rods in this category can easily compress and take on their original state due to unrestricted air movement. The flexibility they possess allows them to easily conform to sealing applications, and limiting the depth of the sealant is also achieved.


Foam with a bi-cellular construction is well-suited for specialty applications, in which standard backer rods would not be suitable. They are ideal in the case of irregular joints, where self-leveling and flowable sealants are used.

Browse our website and contact us today for more information on our backer rod selection and how Alcot Plastics Ltd. can fit your requirements.