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Structural irregularities are not uncommon to encounter in buildings due to the issues that can arise from the coordination of the plan layout, aesthetics, space planning, and other details involved in completing any building configuration. Data from past earthquakes demonstrated that buildings with irregularities have performed poorly and suffered greater damage when compared with buildings having regular configurations. In regular structures, the seismic demands imposed on the structure by the ground motion generally tend to be well distributed which leads to the dispersion of energy dissipation and damage. However, for irregular structures, the seismic demands tend to concentrate in the zone of irregularity, resulting in major damage and failure of structural elements in these zones. The actual load paths may differ from those in the design analysis due to these irregularities. This updated guide based on standards from the 2021 IBC and ASCE/SEI 7-22 explains the impact of building irregularities on structural design with detailed examples of how to analyze and design for different types of buildings in Seismic Design Category B & D.