Two features are observed to be important in the homoepitaxial deposition of 50 monolayers on Pd(100) and Cu(100) at 80 K. First, a fourfold hollow site that is missing one or more of its four supporting atoms on the surface (i.e., an overhang site) can be stable. This increases the surface roughness by allowing defects in the growing surface. Second, multiatom rearrangements occur during growth. These events decrease the local surface roughness by filling deep holes in the surface. Neither of these two features is included in currently used kinetic growth models.