If your lawn is showing signs of distress, with high and low spots in the expanse of grass, you can repair the lawn by evening it out. Adding topsoil to existing lawns is called "top dressing." It involves adding fine topsoil to the entire grass area and spreading it out evenly.
Determine how much topsoil you need to cover your lawn. Find the total square footage of the lawn by measuring its length and width and multiplying these numbers. If you have a great many low spots, add the approximate square footage of the low areas to your square footage measurement.
Buy 2 cubic yards of topsoil for every 648 square feet of grass. This will enable you to lay down 1 inch of topsoil. The topsoil should be fine in texture; grass may not grow through large clumps of soil.
Fill the wheelbarrow with topsoil and dump the topsoil onto the lawn.
Use the rake to spread the topsoil into a 1-inch-deep layer over the grass. Keeping the topsoil at 1 inch will replenish the soil and still allow the grass to grow through it.
Continue adding topsoil to the lawn and spreading it until you have added a 1-inch layer to the entire lawn.
Repeat steps two through five the following year to finish top dressing the lawn.