These construction features are tested for fire spread from below, but NOT from above.

These construction features are tested for fire spread from below, but NOT from above.

• A. Floor Joists
• B. Floor Insulation
• C. Vertical Assemblies
• D. Floor Assemblies

Answer: (D)

The test focuses on how fire moves through the floor–ceiling boundary when the fire starts below and tries to reach the space above. Floor assemblies are the complete system between levels (including floor boards, joists, ceiling finish, and any insulation) and are evaluated by exposing the underside to the fire to see whether heat and flames penetrate upward into the room above. This “from below” orientation reflects basements or crawlspaces fires trying to invade the living space. Other items like floor joists or floor insulation are individual components, not the full assembly being tested for that upward-fire-spread path, and vertical assemblies test fire behavior in a different orientation (through walls), not the floor boundary. Therefore, floor assemblies are the construction feature tested for fire spread from below, but not from above.

The test focuses on how fire moves through the floor–ceiling boundary when the fire starts below and tries to reach the space above. Floor assemblies are the complete system between levels (including floor boards, joists, ceiling finish, and any insulation) and are evaluated by exposing the underside to the fire to see whether heat and flames penetrate upward into the room above. This “from below” orientation reflects basements or crawlspaces fires trying to invade the living space. Other items like floor joists or floor insulation are individual components, not the full assembly being tested for that upward-fire-spread path, and vertical assemblies test fire behavior in a different orientation (through walls), not the floor boundary. Therefore, floor assemblies are the construction feature tested for fire spread from below, but not from above.