What causes bare spots in the lawn may require some outside help to bring the grass back to health. Although grasses have runners above the ground from which the blades shoot, if the grass roots have died or been removed there is no way for the bare spot to fill on its own. Therefore, it is imperative to take on some steps that will help fix the problem faster. - Clean the bare spot area by removing any dead grass or debris and then adding about two inches of soil. - Apply new grass or sod with topsoil to fill the bare spots. - Spread compost around the bare spots and on the weakened grass around the spot. - Add topsoil on the entire spot to improve permeability and hold moisture for the growing grass. - Water the area to keep it moist while the seed or sod are growing. - Maintain a proper level of mineral nutrients to help the grass and soil thrive.