Floor Structures
2011-09-16
A floor structure supports the weight of the occupants, furniture and items in the home. The first floor structure of many single family homes consist of a concrete slab on grade, prefabricated wood trusses, or framed with sawn or engineered lumber. The second floor of many two-story single family homes are constructed with hand framed wood members or prefabricated wood trusses. Trusses are also very commonly used for roof structures, which are covered in the prefabricated wood truss roof structure section.
Besides supporting the weight of the people and items in the home, a floor structure may also serve as a structural diaphragm. This is a structural component often orientated on a horizontal plane, which is stiff and strong enough to collect and transfer horizontal (wind, earth, etc.) loads. Exterior walls or roof planes orientated perpendicular to the direction of wind or other horizontal load transfer loads to the diaphragm (roof or floor structure). The diaphragm then transfers that load to shear walls, or walls that are orientated parallel with the horizontal load. Shear walls transfer the loads to the foundations. Thus the load path (from a horizontal load against a wall (or roof) to the foundation) is completed.
As with any structural component or system, problems may arise from improper construction, damage, or deterioration of a floor structure. Some common problems with floor structures and their causes are discussed in Common Problems and Diagnosis.