Live loads are defined as those loads supported by the member that are not a permanent part of the structure. Live loads can vary in magnitude and location throughout the structure's lifetime. Examples of live loads are human occupants, furniture, vehicles, storage and snow.
Floor live loads for residential structures are normally 40 PSF. Floor live loads for commercial offices are typically 50 PSF. Roof live loads in non-snow regions are normally 20 PSF, with allowances for reductions dependent upon the governing building code. For roof live loads in snow regions please consult your local building code official. All roof live loads are assumed to act vertically upon an area projected on a horizontal plane.