What is the required thickness for fire blocking when using wood panels?

• A. 1-inch thick
• B. 5/8 inch thick
• C. 23/30 seconds thick
• D. 3/4 inch thick

Answer: (C)

Fire blocking is a barrier placed in concealed spaces to slow or stop the spread of fire and smoke between compartments. When wood panels are used for this purpose, the code prescribes a minimum thickness that provides enough mass and rigidity to stay intact and function effectively under heat. The required thickness is 23/30 inch, which is roughly 0.77 inch, essentially just under three-quarters of an inch. This thickness helps the panel resist heat transfer and retain its shape long enough to hinder flame movement through cavities. In practice, using wood panels close to 3/4 inch thick and installing them at the specified intervals with proper fasteners ensures the blocking performs as intended. If other materials are used, the thickness requirements can differ per code, so always verify the current code edition for the exact values.