Which materials are not recommended for use in fire-rated walls?

Fire-rated walls are designed to resist the passage of fire and maintain structural integrity for a specified period. The materials used in these walls must conform to fire safety standards and provide the necessary fire resistance.

Wood is not recommended for use in fire-rated walls because it is a combustible material that can easily ignite and contribute to fire spread. Fire-rated walls typically require non-combustible or limited-combustible materials to effectively delay the spread of flames and protect the building's occupants and structural components.

In contrast, gypsum board, concrete, and steel are all materials that are commonly used in fire-rated construction. Gypsum board is specifically designed to have fire-resistant properties, concrete is inherently non-combustible and can withstand high temperatures, and steel can be treated or coated to improve its fire resistance. Therefore, using wood in fire-rated walls compromises their effectiveness and goes against building codes designed to ensure safety.