NFPA 220 assigns the 2HH designation to which construction type?

• A. Type II
• B. Type III
• C. Type IV
• D. Type V

Answer: (C)

NFPA 220 uses designations that pair a construction type with its fire-resistance characteristics. The suffix “HH” signals heavy timber construction, and the preceding number indicates the fire-resistance rating of the structural system. A two-hour rating combined with heavy timber points to Type IV construction. The large, solid timber members dense with mass char and form an insulating layer that helps the structure maintain strength for about two hours in a fire. That’s why the 2HH designation is assigned to Type IV. Other construction types—noncombustible, mixed exterior with noncombustible interior, or wood-frame—have different markings and expectations, so they don’t carry this 2HH label.