In Type IV construction, the thickness of wood roof decks is nominally at least ______ inches.

In Type IV construction, which is often referred to as "Heavy Timber" construction, the design and materials used prioritize fire safety while maintaining structural integrity. The wood used in the roof decks is essential to this construction type and is typically specified to have a nominal thickness of at least 2 inches. This thickness provides sufficient mass and fire resistance, which is characteristic of heavy timber construction.

The nominal 2-inch thickness serves to meet building code requirements and help ensure that the roof structure can accept loads while also providing enhanced fire performance compared to thinner materials. Thicker materials tend to resist ignition and slow down the spread of fire, which is a crucial safety consideration in commercial buildings.

Using wood roof decks with a thickness less than 2 inches would not align with the principles of Type IV construction, potentially compromising the structural and fire safety qualities that this construction type is designed to provide. Therefore, 2 inches is the correct thickness specified for wood roof decks in this context.