Commercial Building Inspector B2Floor ConstructionEasy
An inspector is evaluating the installation of a new wood floor system in a commercial building. The plans specify the use of fire-retardant-treated wood (FRTW) for the floor joists. Which of the following conditions is NOT permitted for the use of FRTW in floor construction according to the IBC?
- AIn roof construction where the FRTW is exposed to the weather.
- BIn areas where the relative humidity will not exceed 95%.
- CIn concealed spaces where the temperature will not exceed 150°F (66°C).
- DWithin 6 inches (152 mm) of the ground, exposed to weather.
Show answer & explanationAnswer & explanation
Correct answer: D. Within 6 inches (152 mm) of the ground, exposed to weather.
The IBC specifically prohibits the use of fire-retardant-treated wood where it is exposed to the weather, within 6 inches (152 mm) of the ground, or in interior applications where the relative humidity will be greater than 95%.
Why the other options are wrong
- A. FRTW is permitted in roof construction where it is NOT exposed to weather, but this option states it IS exposed, making it also a prohibited condition, however, the question asks for NOT permitted for floor construction, making C the most direct answer.
- B. FRTW is permitted where relative humidity will not exceed 95% for interior applications.
- C. FRTW is permitted in concealed spaces where the temperature will not exceed 150°F (66°C).
FRTW Limitations
Fire-retardant-treated wood has specific limitations on its use, primarily concerning exposure to moisture and high temperatures, to ensure its effectiveness.
- Not permitted where exposed to weather.
- Not permitted within 6 inches of the ground.
- Not permitted in interior applications with relative humidity > 95%.
- Permitted in concealed spaces up to 150°F (66°C).
Memory trick: FRTW fears the wet, the ground, and sun's direct fret.