a. Joist Loads. Joists usually carry a uniform load of materials and personnel. These are live loads. The weight of joists and floor is a dead load. Joists are spaced 16 or 24 inches on the center. Sometimes the spacing is 12 inches, but where such spacing is made necessary by the load, heavier joists should be used. In certain parts of the floor frame, to support heavily concentrated loads or a partition wall, it may be necessary to double the joists or to place two joists together (see Figure 1-16 ).

b. Joists and Sills. When joining joists to sills, be sure that the connection can hold the load that the jolt will carry. A joist resting on the sill and girder is shown in Figure 1-17 . This connection method is most commonly used because it provides the strongest possible joint. The method shown in Figure 1-18 a joist with ledger plates is used when it is not desirable to use joists on top of the sill. The ledger plate should be securely nailed to the sill and girder. If the joist must be notched, it should be securely nailed to the sill and girder. If the joist must be notched, it should not be notched over one third of its depth (to prevent splitting). Joists must be level when framed to girders. If the joist is not the same height as the girder, the joist must be notched (see Figure 1-19 ).

c. Joist Hangers. When it is desirable to have the joists and girders flush, the ends of the joists can be supported by joist hangers (see Figure 1-20 ). Joist hangers support joists at the girders. When joists are hung using joist hangers, the maximum headroom is obtained below the girder.