Leveling an uneven yard corrects drainage issues, eliminates tripping hazards, and improves the overall usability of the space. Achieving a smooth, level surface requires careful calculation to determine the exact volume of material needed, followed by proper material selection and application techniques. Understanding the geometry of the area and the nature of the fill material are the first steps toward a successful project.
Selecting the Proper Soil
The depth of the void determines the appropriate leveling material, which falls into three main categories: fill dirt, topsoil, and sand. Fill dirt is essentially subsoil, composed of clay, sand, and rock, containing very little organic matter or nutrients, making it unsuitable for plant growth. Its dense nature makes it the ideal choice for filling deep voids or changing the grade, providing a stable base that resists settling.
Screened topsoil, the uppermost layer of earth, is rich in organic matter and nutrients, which is necessary for establishing new grass or garden beds. If the leveling required is shallow—typically less than four to six inches—and the area will support vegetation, topsoil is the preferred material for the surface layer. For minor leveling of an existing lawn, a mix of topsoil, compost, and fine sand is often used for topdressing, which improves drainage and smoothness. The material chosen should always be clean and screened to ensure it is free of large debris, roots, or contaminants.
Determining Existing Surface Dimensions
Accurately calculating the required volume begins with determining the area’s dimensions and the average depth of the low spots. Start by measuring the length and width of the area to be leveled in feet, which provides the square footage of the project. For irregularly shaped spaces, dividing the area into smaller, manageable squares or rectangles simplifies this initial measurement.
Determining the depth needed requires establishing a consistent reference plane using stakes and string lines. Drive wooden stakes into the ground around the perimeter of the area, then tie a taut nylon string between them. A small line level attached to the string ensures the line is perfectly horizontal, creating a consistent height reference across the entire section.
Measure the distance from the taut string down to the existing ground at multiple points within the work area, especially at the deepest depressions. These measurements identify the varying depth of the fill required. By averaging these depth measurements, or by calculating the volume for several smaller, uniform sections, a reliable average depth for the entire area can be established.
Calculating Soil Volume Requirements
Once the length, width, and average depth are known, the volume of material is calculated using the formula: Length × Width × Depth. Since all three dimensions must be in the same unit, convert the depth from inches to feet by dividing by 12 (e.g., three inches becomes 0.25 feet). This calculation yields the volume in cubic feet.
The resulting volume is in cubic feet. Because soil is sold by the cubic yard, this total must be converted by dividing the cubic footage by 27, as there are 27 cubic feet in one cubic yard. This final figure represents the estimated volume of material needed.
Account for compaction, as the loose material will settle when spread and tamped down. Fill dirt and topsoil require additional volume to compensate for this loss of air space. Adding a safety margin of 10 to 20 percent extra material is recommended to ensure enough material remains to achieve the desired final grade after compaction.
Preparing the Site and Spreading the Fill
Before placing any new material, clear the existing area of debris, large rocks, and organic matter to prevent future settling or decomposition. If the existing soil is heavily compacted, lightly loosening the surface with a rake or tiller can help the new fill material bond more effectively. For larger fills, the material should be brought in and spread in uniform layers, known as lifts, which should not exceed four to six inches in loose thickness.
Compacting each layer individually creates a stable, long-lasting surface that resists future settlement. Compaction is most effective when the soil is at its optimum moisture content (damp but not saturated), meaning the soil holds its shape when squeezed without releasing water. A plate compactor or roller should be passed over each lift until it is firmly packed before adding the next layer.
For the final layer, a long, straight edge, such as a two-by-four board, can be used as a screed to scrape the material across the surface, ensuring a perfectly flat finish. This technique smooths out minor inconsistencies and eliminates small bumps or depressions. The goal is to achieve a consistent grade that slopes slightly away from any structures, typically at a rate of one to two percent, to promote proper drainage and protect the foundation.