Differentiate thickness coverage from coverage uniformity.

• A. Coverage uniformity measures depth at a point; thickness coverage ensures even distribution across the area.
• B. Both terms refer to the same concept.
• C. Only thickness coverage matters.
• D. Thickness coverage measures depth at a point; coverage uniformity ensures even distribution across the area; both are required for performance.

Answer: (D)

Thickness coverage refers to how deep the coating is at a specific location, while coverage uniformity is about how evenly that coating is spread across the entire area. For fireproofing to perform as rated, you need the required thickness at measured points and you also need that thickness to be consistently distributed across the surface. If you have the right depth at one spot but areas nearby are too thin, the protection can fail. Conversely, you could have a uniform laydown that never reaches the required thickness anywhere, also failing the rating. So both aspects matter: the depth at a point and the even distribution across the area.