For a two-story slab-on-grade construction, what must the load-bearing capacity of the soil be, at a minimum?

In slab-on-grade construction, particularly for two-story buildings, it is crucial to ensure that the load-bearing capacity of the soil can adequately support the weight of the structure and its occupants. The minimum load-bearing capacity of the soil is dictated by both building codes and safety standards, which take into account factors such as the weight of the materials used and potential live loads from furniture and people.

A minimum load-bearing capacity of 3000 psf is required for a two-story slab-on-grade construction to ensure that the foundation can handle not only the static loads but also any dynamic loads that may occur during the building's lifetime. This capacity also allows for a safety margin to accommodate potential variances in soil conditions and moisture variations that could affect the soil's load-bearing ability over time.

Building codes tend to set this threshold as a standard to prevent structural issues that could arise from inadequate support. A higher minimum load-bearing capacity helps in ensuring the longevity and stability of the structure, especially against settling or shifting that can occur due to changes in soil conditions. Therefore, recognizing 3000 psf as the correct answer reflects a fundamental understanding of safety and construction standards for this type of building.