This comprehensive guide focuses on the importance of base stiffness and base connections, along with the potential impact of foundation settlement on steel portal frames. Clause 126.96.36.199 of BS 5950: Part 1 provides guidelines on the stiffness of the base of a column, and the base stiffness should be treated as a beam stiffness. Other base support options, such as vertical and horizontal support options of rigid, free, and spring stiffness, are also discussed. Foundation settlement can have a significant impact on the bending moments of a frame, and isolated settlement can be more damaging than overall settlement. The article also provides an example of a triangulated roof truss supported by semi-rigid bases and highlights the benefits of analyzing with nominally pinned bases. By following the guidelines outlined in the article, designers can model and analyze base connections accurately and minimize the impact of foundation settlement on a structure’s bending moments.