Many homeowners choose the ease and convenience of sod when installing a new lawn or reestablishing an older one. Preparing soil for sod installation can be a long process that takes as long or longer than installing the sod itself; it involves removing all existing grasses, tilling the soil, adding soil amendments or topsoil, rough grading the yard, tilling again, then draining and installing sprinklers prior to final level grading. Fortunately, a property's existing soil is often good enough for sod installation, and many homeowners choose to lay sod directly over grass.
Kill any weeds that exist in the current yard. Apply a specialized weed killer or a glyphosate-based herbicide. Glyphosate-based herbicides also kill grass, but the sod will cover the existing grass; wait until the herbicide is no longer active in the soil to lay sod.
Raise the height of any sprinklers or drainage pipes. Calculate the final height of the new lawn, including the height of topsoil and the height of the sod panels, then use that value to determine how much to raise the hardware.
Mow the existing grass as short as possible. Rake the yard to remove any clippings, leaves or large foreign debris such as rocks or sticks.
Apply a 2- to 3-inch layer of topsoil. Sod needs loose soil to establish its roots. Apply a high phosphorus fertilizer with a 1-2-1 ratio on top of the topsoil. Smooth the topsoil and fertilizer with a lawn roller.
Lay the sod within 24 hours of purchase. Normal sod installation techniques should be used when laying sod directly over grass.