Concrete and steel framed floors with brick, clay tile, and concrete decking constructed in the late 1800s and early 1900s are described. Methods of documenting existing construction and condition of the structure are discussed. Procedures for calculating structural capacity and confirmatory load tests are presented. These types of floor systems have been found to have strength and stiffness greater than that predicted by simplified calculation due to composite action, connection fixity, and two-way action. A case study of in situ load testing of a flat clay-tile arch floor system and discussion of the measured behavior demonstrates these principles.