Exterior walls with a fire separation distance of less than 10 feet must provide what level of fire rating?

When exterior walls have a fire separation distance of less than 10 feet, building codes typically require these walls to provide a fire rating that is effective on both sides. This is necessary to ensure that if a fire occurs on one side of the wall, the fire's spread is mitigated and doesn't easily penetrate to the other side. The rationale behind this requirement involves the increased risk of fire exposure to neighboring properties or structures when they are in close proximity.

In essence, walls that are too close to other buildings must be robustly rated for fire resistance to protect both the structure itself and adjacent structures. This not only helps in preventing the flames from breaching the wall but also minimizes the chance of smoke and heat affecting the nearby property. A wall rated for one side would not provide sufficient protection in this scenario, as it could potentially allow flames and smoke to cross over to the neighboring side where an absence of protection could lead to further fire risk.