Joint Sealing Sealant Passive Fire Protection Article

Sika provides comprehensive solutions where fire resistant construction is required such as commercial, public and residential buildings, steel structures and others. Fire resistant sealants, fillers and backing materials for linear seals as well as solutions for penetration seals enable safer buildings and infrastructure to be built. Passive fire protection applications for compartmentations can be divided into the following three main groups: linear joint seals, cavity barriers, penetration seals.

Linear Joint Seals

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 wall and floor.

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

PE backer rod and fire resistant sealant
Image: PE backer rod and fire resistant sealant

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

Fire resistant silicone sealant for linear seals in walls and floors
Image: Fire resistant backer rod and standard joint sealant

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.

Fire resistant expansion foam
Image: Fire resistant expansion 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.

Cavity Barriers  

Cavity barriers are passive fire protection systems similar to linear (floor-) seals but wider that standard joints in most cases.

Cavity barriers typically can be found between floor slabs and curtain wall facades or in wide gaps within a building. Such cavity barriers are designed to avoid the spread of fire from one floor to the other which is one of the major threats when highrise buildings catch fire.

Fire Resistant Cavity Barrier

Service Penetration Seals

Service penetration seals are passive fire protection systems designed to maintain the fire resistance of a building element or section – wall or floor – where services such as cables, cable trays, pipes or ventilation ducts pass through them.

The vast number of different building materials and different services and the types of penetrations that can be required, leads to a wide variety of different solutions for sealing around these service penetrations. The result is that for most of these penetration sealing applications, several alternative solutions, with different systems and products can be used – if the combination has been tested.

One of the challenges with sealing around penetrations is that certain services (e.g. combustible pipes) will melt in the event of a fire, which results in even larger apertures that must be closed immediately. For this type of application, expanding intumescent materials are usually a very effective solution.

Fire Resistant Penetration Seal Illustration
Passive fire protection in the floor with Sikacrete - Expanding Intumescent Material Illustration

What Can Influence the Fire Resistance of a Building Element?

The following parameters have an influence on the fire resistance of a building element and hence of its classification. Therefore it is crucial to know all relevant details to select the right product.

  • Types of involved building material e.g. concrete/steel
  • Element orientation: horizontal (floor) or verticall (wall)
  • Element thickness
  • Joint dimension (width, depth)
  • Joint configuration: Single seal exposed/unexposed, double seal
  • Expected joint movement
Christian Voellm

Christian Völlm
Corporate Market Development Manager
Target Market Sealing & Bonding
Sika Services AG