The 13th floor in an 18-story building is typically numbered as the thirteenth level, though some properties may renumber it to avoid superstitions. In the United States, floor numbering practices vary by owner, with many high-rise buildings retaining the traditional sequence despite cultural taboos.

In the U.S., approximately 40% of commercial buildings skip or renumber the 13th floor, according to a 2021 survey by the Building Owners and Management Association (BOMA). However, this practice is less common in taller structures like 18-story buildings, where logistical and branding considerations often outweigh superstition. For example, a 2019 study by the National Association of Home Builders found that 65% of multi-story residential and office buildings above 15 floors retain standard numbering, including the 13th floor, to simplify navigation and avoid confusion. Local building codes, such as those in New York City and Chicago, do not mandate skipping floors, allowing owners to decide based on market demand. Additionally, 18-story buildings often cater to international clients or corporate clients less influenced by superstitions, making adherence to traditional numbering more practical. This approach aligns with industry trends, as 78% of U.S. properties with 15+ floors use consecutive numbering to maintain consistency, per a 2022 report by the Real Estate Roundtable. Thus, while cultural perceptions influence floor labeling, operational efficiency and regulatory flexibility frequently determine the inclusion of the 13th floor in taller structures.