Laying sod correctly in your yard will take several days in all. You’ll need to remove all old sod, vegetation and debris on the site, and ensure the area is ready to lay sod. Whether or not you add topsoil will depend on the amount of rich soil you already have at the area and what you want to do for grading.
According to the University of Rhode Island Landscape Horticulture Program, grass roots go down 5 to 6 inches deep. If the topsoil layer of your lawn isn’t thick enough, the grass won’t be able to root properly. After you remove all the vegetation from the area, you’ll need to rototill the existing 4 to 6 inches to loosen and break up soil. Sod needs direct contact with the soil to grow best.
If you don’t already have the sod on-hand, contact your sod company to ask them how much soil they leave on their sod pieces. To determine if you need more sod, you’ll need to compare the thickness of the soil line on your sod with the surrounding surfaces such as driveways and sidewalks, notes the All About Lawns website.
For example, if your sod has a soil thickness of 2 inches, you’ll need to grade the area so that it is 2 inches below the surface of sidewalk.
Don’t just put the new topsoil over the existing soil, mix it up with a tiller to integrate the nutrients throughout. It’s difficult for sod roots to grow through distinct layers of soil. Keep in mind that loose soil settles, so 6 inches of loose soil will eventually settle down to 5 inches.
JB Instant lawn suggests that if you do need to bring in topsoil, introduce at least 3 inches of new soil and then integrate into the existing soil. If you don’t need three inches of soil over the entire area, consider using it elsewhere in your yard, or grading the area away from your home by creating gradual slopes. Not only do gentle slopes help with drainage issues, but they also add visual interest to the lawn.