The document discusses various types of irregularities in building structures that can compromise their ability to withstand disasters like earthquakes. It defines plan and vertical irregularities as classified by building codes. Plan irregularities include torsional issues from uneven mass distribution, re-entrant corners, discontinuities in structural elements, and non-parallel supporting systems. Vertical irregularities consist of abrupt changes in mass or stiffness between stories like soft stories. The document provides examples and solutions to avoid different types of irregularities in building design and improve structural integrity during disasters.