How far below the foundation should a trench extend?

The correct depth for a trench to extend below the foundation is 24 inches. This depth is commonly recommended to ensure that the trench is sufficiently below the frost line or any potential disturbances that could affect the stability of the foundation. Extending the trench to this depth helps prevent issues such as heaving or settling, protecting the structural integrity of the building. Furthermore, a 24-inch depth allows for any necessary adjustments related to drainage and utility installation, ensuring compliance with building codes and providing a secure base for the construction processes that may follow.