We have performed molecular dynamics simulations to determine the adsorption and diffusion activation energies of Si and C adatoms on the single stepped surfaces, S-A, S-B(n) and S-B(b), of SiC(001). We find that Si adatoms, unlike C adatoms, have to overcome a barrier at the step edge before it can diffuse from the upper to lower ledge. From an examination of C adatom diffusion events, we conclude that layer by layer growth is most likely when there are S-A type steps.