Linear joint seals are passive fire protection systems designed to maintain the required building fire resistance across a separating element plus, if and where relevant, to accommodate a defined degree of movement. Linear joint seals can be found in walls, floors and in so called head of wall applications - joints between wall and ceiling or between wall and floor.

A fire resistant linear joint seal can be achieved by different approached:

Illustration showing double linear seal joint sealant

The most common way is to use a fire resistant joint sealant in combination with a standard PE backer rod. In this case only the sealant is usually required to provide fire resistance while the backer rod is
considered as sacrificial.

Linear Seal Backer Rod

An alternative approach is to use a fire resistant backer rod - typically based on an inorganic fire resistant material like mineral wool - and combine it with a standard joint sealant. In this case the fire resistance of the linear seal is provided by the backer rod and the joint sealant is used to accommodate limited movement, ensure water tightness and provide mechanical protection.

Linear Seal Foam

The third option is to seal the joint with a fire resistant expanding foam. This system is only recommended where the joints have very limited movement and are not exposed to water, UV radiation or mechanical impact.