Types of fundations used for steel-framed buildings were set out above. The type selected for pervailing soil conditions can affect the choice of superstructure. One common case is to use pinned bases in poor soil conditions because fixity wuold be expensive to achieve. Again, where provision must be made for differential settlement, buildings of simple design perform better than those of rigid design. If a monolithic saft or basement foundation is provided, the super structure can be designed independently of the foundation.