Sod consists of pre-grown grass turf, harvested in rolls or squares, and laid directly onto prepared soil. For a successful, long-lasting lawn, it is necessary to remove all existing grass and vegetation before installation. Skipping this preparatory step creates an unstable foundation and jeopardizes the new turf’s ability to establish a healthy, deep root system. Proper removal ensures the new lawn has the best chance to flourish immediately.
Why Removing Existing Vegetation Is Essential
Laying new sod over old turf creates a sandwich effect that compromises the health of the new grass. The shallow roots of the freshly laid sod are blocked from reaching the underlying soil by the dense, matted layer of existing grass and its root system. This barrier prevents the direct root-to-soil contact necessary for the new sod to anchor itself and absorb moisture and nutrients effectively. Without this connection, the new turf will struggle to survive, resulting in a weak, patchy lawn.
The existing organic matter, whether alive or recently killed, acts as a competitor for water and nutrients. As the old grass decomposes beneath the new layer, it can generate heat, which prevents proper establishment of the new roots. This decomposing layer also creates air pockets and an unstable base. This instability will cause the surface to settle unevenly over time, transforming a smooth new lawn into a lumpy surface.
Old turf can harbor pests and diseases, which may immediately infect the vulnerable new sod. The dense thatch layer of the old grass also impedes drainage, causing water to pool and creating an environment favorable for fungal growth and root rot. Removing this layer eliminates these biological threats. This ensures the new sod is placed in a clean, stable environment, allowing its roots to penetrate the soil deeply.
Methods for Clearing the Area
Clearing the area involves actively killing and physically removing the old turf before soil preparation begins. One effective method involves chemical eradication using a non-selective herbicide, such as glyphosate. This systemic chemical is absorbed by the foliage and travels through the plant to the root system, ensuring the entire plant is killed.
After application, allow seven to ten days for the herbicide to fully work and the grass to completely die. Follow all label instructions, especially regarding safety and avoiding drift onto desirable plants. Once the existing turf is completely brown, it must still be physically removed, not tilled into the soil, to prevent issues associated with decomposing organic matter.
For mechanical removal, renting a sod cutter is the quickest solution, particularly for medium to large areas. This specialized equipment uses a sharp blade to slice horizontally beneath the turf, cutting the grass and a shallow layer of roots into manageable strips. These strips are then rolled up and removed from the site, taking the old root mass and thatch layer with them.
Soil solarization is a non-chemical option that uses heat from the sun to kill vegetation and weed seeds in the topsoil. This method involves mowing the grass short, watering the area, and covering it tightly with clear plastic sheeting to create a greenhouse effect. The edges of the plastic must be secured with soil to trap the heat. This process typically requires four to eight weeks during the hottest part of the year for success.
Final Soil Grading and Amendments
Once all dead grass and debris are removed, prepare the subgrade to ensure optimal root growth and drainage. The soil should be tilled to a depth of four to six inches to loosen compaction and improve aeration and water infiltration. Tilling allows the new sod roots to penetrate the soil easily and bond quickly with the underlying earth.
Before final grading, perform a soil test to determine the existing pH and nutrient levels. Turfgrass prefers a slightly acidic pH around 6.5, and amendments like lime or sulfur may be necessary to correct the balance. Incorporating a starter fertilizer, which is higher in phosphorus to encourage root development, and organic matter like compost into the tilled soil will boost fertility.
After incorporating amendments, the area must be finish-graded with a rake to ensure a uniform surface and proper drainage away from structures. The final grade should be approximately three-quarters of an inch below any sidewalks or patios to account for the thickness of the sod. Finally, the soil surface should be lightly compacted using a lawn roller. This removes air pockets and creates a firm seedbed, ensuring solid contact for rapid establishment.