Soil leveling is the single most important factor for achieving a successful, healthy, and visually appealing lawn from newly laid turf. A smooth, consistently graded surface ensures the sod establishes itself uniformly, preventing the formation of dips that collect water or humps that get scalped by a lawnmower later on. This preparation stage dictates the long-term quality and low-maintenance nature of the final lawn. Proper preparation provides the new grass with an ideal foundation for root growth and nutrient uptake from the moment it is installed.
Preparing the Area for Soil Work
The first step in preparing the ground involves completely clearing the entire area of all existing vegetation and debris. This includes removing old grass, weeds, and any buried materials like stones larger than a matchbox, construction rubble, or roots. Thorough removal of plant matter prevents competition with the new turf for water and nutrients during the initial establishment phase. If existing weeds are extensive, a non-selective herbicide like glyphosate can be used, but a waiting period of several weeks is necessary before proceeding.
Once the area is clear, the soil must be loosened to a depth of at least 15 centimeters (about 6 inches) to alleviate compaction. Tilling or rotovating the soil allows for better air exchange, water penetration, and root development for the sod. At this stage, soil amendments should be incorporated, guided by a soil test to determine pH and nutrient deficiencies. For instance, a heavy clay base benefits from the addition of gypsum and sand to improve drainage, while sandy soil requires organic matter like compost. The goal is to create a nutrient-rich, well-aerated base that is slightly acidic, ideally with a pH between 6.0 and 7.5.
Setting Drainage and Bulk Soil Movement
Establishing the rough grade is the process of shaping the overall contour of the land to manage water runoff effectively. This step prevents water from pooling in low spots or running back toward structures, which can cause foundation damage. A slight slope away from any buildings is necessary, with a minimum grade being a drop of 1 to 2 inches for every 10 feet of distance (approximately a 1-2% slope).
To set this grade, use stakes and string lines to mark the desired height and pitch across the entire area. The string line acts as a visual reference, ensuring the soil movement follows the intended downward slope. This is the phase for bulk soil movement, where large quantities of topsoil are spread to fill major depressions or to raise the overall level of the lawn area.
It is often recommended to use a quality topsoil or a specialized turf underlay mix, such as an 80/20 sandy loam, to create a consistent layer of 10 to 15 centimeters (4 to 6 inches) after firming. This initial spreading of the soil is referred to as “rough leveling,” focusing on the large-scale contours. The rough grade must be maintained throughout the leveling process to ensure that all surface water drains away quickly.
Achieving a Smooth, Level Surface
After establishing the rough grade, the focus shifts to achieving the fine, uniform surface necessary for turf installation. This precision work ensures the sod will have maximum contact with the soil underneath, which is essential for rapid rooting. A landscape rake is used extensively at this stage to break up any remaining large soil clumps and to create a finely textured, even surface.
The process of “screeding” is the most effective method for final leveling, involving a long, straight board, often called a screed board or leveler. This board is pulled across the soil to shave down high spots and simultaneously deposit that excess material into low areas.
To eliminate subtle irregularities, the cross-raking method is employed, raking the surface in multiple directions—such as north-to-south, then east-to-west, and diagonally. Repeat the screeding and raking until the surface is uniformly smooth and free of undulations. The soil level should be approximately 20 to 40 millimeters (less than 2 inches) below any surrounding hard edges like sidewalks or patios to account for the thickness of the new turf.
Immediate Steps Before Laying Turf
Once the soil is finely graded, the surface must be lightly firmed to prevent excessive settling after the turf is laid. This can be accomplished by walking over the area in a crisscross pattern using small, shuffling steps, or by using a water-filled roller set to its lightest weight. The goal is to create a firm, yet not overly compacted, seedbed that provides a solid base for the sod without hindering root growth.
Immediately prior to installation, a starter fertilizer should be applied to the newly leveled soil. This specialized fertilizer contains a high concentration of phosphorus, the nutrient beneficial for stimulating strong and rapid root development. The fertilizer should be spread uniformly across the surface according to the manufacturer’s directions and should not be raked in.
The final preparatory action is a light watering of the soil to settle the surface and reduce dust. The soil should be slightly moist, but never saturated, as laying sod on overly wet ground can lead to compaction and drainage issues. This moisture ensures the sod rolls are placed directly onto a receptive, slightly damp bed.