What is the fire-resistance time assigned to ½ inch gypsum wallboard membrane in an untested fire-resistance-rated assembly?

• A. 15 minutes
• B. 20 minutes
• C. 25 minutes
• D. 30 minutes

Answer: (A)

The fire-resistance time assigned to ½ inch gypsum wallboard membrane in an untested fire-resistance-rated assembly is based on its recognized performance properties in terms of preventing the spread of fire. Gypsum wallboard is widely used in construction for its fire-resistance features, and industry standards provide specific time ratings for assemblies that incorporate this material.

In this case, the assigned fire-resistance time of 15 minutes reflects the minimum performance expected from a ½ inch gypsum wallboard when utilized in such assemblies without additional testing. This means that the wallboard can provide effective protection against fire for at least 15 minutes, which is a critical factor for building safety and compliance with fire codes during occupancy.

The other options propose higher time ratings that are either typically associated with thicker gypsum wallboard or specific tested assemblies which have received greater fire-resistance ratings due to additional materials or configurations. Therefore, understanding the context of the material's performance helps clarify why 15 minutes is the correct answer in this specific scenario.