Sod offers an immediate green lawn appearance. While it might seem convenient to unroll new turf over an existing lawn, this practice is strongly discouraged and leads to failure. Successful sod establishment depends entirely on the new grass roots rapidly knitting into the native soil beneath. Skipping site preparation steps to save time results in a temporary lawn that struggles to survive.
Why Sodding Over Existing Turf Fails
New sod fails when laid over existing turf due to a lack of proper root-to-soil contact. The dense layer of old grass, thatch, and surface debris acts as a physical barrier, preventing the new sod’s roots from penetrating the underlying native topsoil. This barrier creates a shallow rooting environment, leaving the new grass unable to anchor itself or access deeper moisture reserves.
The existing grass also creates intense competition for resources. Its established root system aggressively consumes water and nutrients, effectively starving the vulnerable, newly laid sod. Furthermore, a thick layer of old, decomposing turf underneath the sod can lead to uneven settling, creating air pockets and poor drainage. These conditions foster disease and prevent uniform water absorption, quickly compromising the health of the new lawn.
Essential Site Preparation for Successful Sodding
Complete removal of the existing lawn is the first necessary step. This can be achieved by applying a non-selective herbicide to kill the old grass, followed by mechanical removal using a sod cutter to lift the dead turf.
Once the old turf is removed, the soil must be tilled to alleviate compaction and promote root growth. Tilling the ground to a depth of 4 to 6 inches allows the sod’s roots to easily penetrate and establish themselves in the subsoil. During this tilling process, incorporating organic material, such as compost, significantly improves the soil’s structure, enhancing drainage and increasing water retention.
The final step involves grading and leveling the area to ensure proper water flow. The soil surface should be fine-graded with a rake to remove rocks or large clumps and create a smooth, firm seedbed. Establish a gentle slope away from structures to prevent water from pooling and causing drainage issues. The finished grade should sit about one inch below surrounding hard surfaces, such as sidewalks or driveways, to account for the thickness of the new sod.
The Proper Steps for Laying and Securing New Sod
The process of laying the sod begins by dampening the surface slightly with water. The first roll should be unrolled along a straight edge, taking care not to stretch the turf. Subsequent rolls should be laid in a staggered or “brickwork” pattern to prevent long, continuous seams that are prone to drying out.
Ensure the edges of each sod piece are tightly butted against one another without overlapping. Gaps will not fill in naturally, as the sod tends to shrink slightly as it dries, widening any existing spaces. A utility knife is used to trim pieces to fit around curved areas, sprinkler heads, and edges.
After all the sod is laid, use a water-filled lawn roller to press the turf firmly onto the prepared soil. This action eliminates air pockets between the sod and the soil, which are a major cause of root desiccation. This ensures maximum contact for efficient water and nutrient uptake. The newly installed sod must be immediately and deeply watered to prevent the roots from drying out.