What is the minimum width of a foundation for a two-story light frame house built on clay soil?

The minimum width of a foundation for a two-story light frame house built on clay soil is typically determined by the load-bearing requirements and the characteristics of the soil. Clay soils can be susceptible to expansion and contraction based on moisture content, which can impact the stability of a foundation. When constructing a foundation in these conditions, a wider footing is generally recommended to distribute the loads more evenly and prevent settling or cracking.

A 12-inch width offers enhanced stability and load distribution, which is critical for supporting the weight of a two-story structure, especially in clay soils that require more robust support due to their variable nature. This wider foundation helps ensure that the building is secure and less likely to experience issues related to soil movement.

In contrast, narrower foundations like 6 inches, 8 inches, or 10 inches might not provide sufficient support in clay environments, particularly for a structure that has significant vertical loading like a two-story home. Therefore, the choice of a 12-inch width aligns with best practices in building codes that prioritize safety and structural integrity in challenging soil conditions.