Choosing a fire-rated door assembly involves consideration of which primary feature?

When selecting a fire-rated door assembly, the primary feature to consider is the self-closing mechanisms. These mechanisms are critical because they ensure that the door closes automatically after being opened, which is essential for maintaining the integrity of the fire barrier. A self-closing door helps to prevent the spread of smoke and fire between different areas of a building, thus enhancing safety and compliance with building codes and fire regulations.

While design aesthetics, acoustic properties, and lightweight structure may be relevant in specific scenarios, they do not play as pivotal a role in the primary function of a fire-rated door. The self-closing mechanism directly contributes to the door's effectiveness in fire prevention and safety, making it essential for fire-rated assemblies.