A permit is not required for retaining walls that are what height or less?

The correct answer is based on the provisions outlined in the International Residential Code (IRC) regarding retaining walls. According to the IRC, a permit is typically not required for retaining walls that are less than 4 feet in height. This regulation helps streamline the construction process for smaller, less complex projects, minimizing the administrative burden on builders and homeowners.

When retaining walls are over this height threshold, they present greater engineering challenges, such as increased lateral earth pressure and potential drainage issues. These factors can affect the overall stability and safety of the structure, thus requiring a higher level of scrutiny and potentially a permit to ensure compliance with safety and construction standards.

In summary, retaining walls that are 4 feet tall or less do not necessitate a permit, as this height is generally considered safe and manageable without the need for extensive oversight or structural calculations.