What is the minimum fire-resistance rating for nonbearing exterior walls in Group M occupancies with a separation distance of less than 5 feet?

In determining the minimum fire-resistance rating for nonbearing exterior walls in Group M occupancies (which include mercantile establishments), the applicable building codes specify that when the separation distance from property lines or adjacent structures is less than 5 feet, nonbearing exterior walls must be designed to provide adequate fire protection.

The requirement for a 2-hour fire-resistance rating reflects the need to protect against potential fire spread from nearby properties. This level of fire-resistance is crucial because in closer proximities, structures face higher risks in case of a fire. A 2-hour rating is deemed necessary to ensure that a fire originating in one building does not easily spread to an adjacent structure, providing a sufficient barrier to protect life and property.

Higher ratings, such as 3 or 4 hours, are typically reserved for more hazardous occupancies or situations where additional protection is justified due to increased fire load or proximity to other structures. Therefore, for Group M occupancies within less than 5 feet of another building, the established requirement is a fire-resistance rating of 2 hours, striking a balance between fire safety and construction practicality.