North Carolina Building Contractor License Practice Exam

What is the minimum compressive strength required for concrete foundation walls at 28 days?

1. 3000 psi

2. 2500 psi

3. 4000 psi

4. 5000 psi

The correct answer is: 2500 psi

The minimum compressive strength required for concrete foundation walls at 28 days is typically 2500 psi in many building codes, including the guidelines followed in North Carolina. This strength is considered adequate for a variety of structural applications, particularly in non-load-bearing situations or where the walls will not experience significant stress from the surrounding soil or additional loads. Choosing 2500 psi reflects the goal of achieving a balance between structural integrity and cost-effectiveness when constructing foundation walls. Strengths greater than this, such as 3000 psi, 4000 psi, and 5000 psi, may be specified in certain situations where higher load capacities are required, such as for heavy structures or in areas subjected to aggressive environmental conditions. However, the 2500 psi standard represents the baseline requirement to ensure that the concrete can adequately support typical residential or light commercial foundation structures.