To where should all exterior footings and foundation systems extend?

All exterior footings and foundation systems should extend beneath the frost line to prevent the effects of frost heave during the colder months. In regions with seasonal frost, the ground can expand and contract as it freezes and thaws. This movement can cause significant structural damage if footings are not deep enough to stay below the frost line, which is the depth below the ground surface where the soil temperature remains above freezing. Ensuring that the footings are placed below this line stabilizes the foundation and maintains the integrity of the building throughout various weather conditions.

While the water table and ground surface factors are important in construction, they do not specifically address the need for footings to prevent frost-related issues. Additionally, building at the property line is more about zoning and setbacks rather than the structural integrity of the foundation. Therefore, the requirement to extend footings beneath the frost line is a critical aspect of maintaining a safe and stable structure in any frost-prone area.