Sealing Firewalls

Select sealants that:

are compatible with their intended surfaces,

allow for differential expansion and contraction between dissimilar materials,

meet the requirements of the applicable fire safety code (e.g. thermal or ignition barriers), and

for use inside the pressure boundary select low volatile organic compound (VOC) sealants that meet independent testing and verification protocols

Select materials that:

adequately support applied load and are permanent air barriers,

meet the requirements of the applicable fire safety code (e.g. thermal or ignition barriers), and

for use inside the pressure boundary select low volatile organic compound (VOC) materials that meet independent testing and verification protocols

Install backing or infill in any gap or crack greater than 1/4"

Install rigid backing or infill for gaps or cracks greater than 3" using mechanical fasteners

Once installed, backing or infill will not bend, sag, or move

Remove any material from the sealing area that will prevent full adhesion of the selected sealant

Apply a continuous seal at all seams, cracks, joints, edges, penetrations, and connections of the firewall while applying sufficient pressure to push sealant into any gaps or cracks and contact any backing or infill material required

If firewall assembly is not monolithic (e.g., balloon framing, CMU, open chase, attic bypass, or with similar penetration through the attic floor plane), attic floor plane penetrations within the firewall assembly will be accessed through the firewall, fully sealed, and firewall surface restored to prevent current or future breaches of the firewall below the attic floor plane from establishing an air flow path to the attic space