An introduction to FM 4411 ‐ Approval Standard for Cavity Walls and Rainscreens.
Until now, there have been no industry standards that fully addressed the interior fire risks associated with cavity wall and rainscreen wall construction. Even tests required by the current building codes, such as NFPA 285, do not fully evaluate the internal fire risk and fire spread of cavity and rainscreen walls – risks such as hot work, grinding sparks, and electrical shorts.

This new standard published in late 2016 helps to mitigate the risk against fires due to the air gap in concealed wall spaces.

FM Approvals created FM 4411 because existing tests may not determine fire risk adequately. While testing is required by Building Codes, these Codes are focused on life safety – to get the people out safely ‐ and then the building can burn down.

FM Global and FM Approvals are focused on property loss prevention – which goes hand in hand with life safety: get the people out and prevent property damage. As the property insurer, FM Global requires a much higher level of fire performance than Code. Unlike small scale tests, FM testing is correlated to large scale fire tests that simulate actual fire conditions.

Consider a common fire scenario: Ignition occurs in a cavity wall, spreads within the cavity and leads to roof fire in attic. No sprinklers or smoke detectors are provided in the attic. The building is a total loss.