The Foundation of a Healthy Lawn
Whether you are filling in a massive sinkhole, building raised garden beds, or grading a new yard before laying sod, you need Topsoil.
Topsoil is the uppermost layer of the earth's crust (usually the top 2 to 8 inches). It is incredibly rich in organic matter, microorganisms, and nutrients. Beneath the topsoil is the "subsoil," which is mostly dense clay and rock where nothing will grow. If a contractor scrapes away your topsoil during construction and tries to lay sod directly on the hard clay subsoil, the grass will die within weeks.
Buying topsoil from a home improvement store in 40-pound plastic bags is incredibly expensive and physically exhausting. For any project larger than a few flower pots, you must order bulk topsoil from a landscape supply yard, where it is delivered in a dump truck and sold by the Cubic Yard.
The Types of Bulk Soil
When you call the landscape yard, you must specify what kind of soil you need based on your project:
- Fill Dirt: This is the cheapest dirt available. It is un-screened subsoil containing massive rocks, clay chunks, and zero nutrients. It is used exclusively to fill deep holes or change the structural grade of a yard. You cannot grow grass in it.
- Screened Topsoil: This is pure topsoil that has been run through a massive mechanical sifter (usually a 1/2-inch or 3/4-inch screen) to remove all rocks, roots, and sticks. This is the absolute standard for laying sod or seeding a new lawn.
- Garden Mix (50/50 Blend): This is a premium mixture of 50% screened topsoil and 50% organic compost. It is very expensive and is used exclusively for filling raised vegetable garden beds where maximum nutrient density is required.
How to Calculate Cubic Yards
Topsoil is a three-dimensional volume measurement. You must calculate the total cubic feet of your project area and convert it into cubic yards.
The Formula
- Measure the Length and Width of the area you are covering in feet.
- Determine your desired Depth in inches (e.g., you need 4 inches of topsoil to grow grass).
- Convert the depth into feet by dividing by 12. (e.g., 4 inches ÷ 12 = 0.333 feet).
- Multiply Length × Width × Depth(in feet) to find the Total Cubic Feet.
- Divide the Total Cubic Feet by 27 to convert to Cubic Yards.
- Add a 10% to 15% Settlement Factor. (Topsoil is very fluffy when dumped off the truck. After the first heavy rain, it will compress and sink significantly).
Cubic Yards = ((Length × Width × (Depth ÷ 12)) ÷ 27) × 1.15
Example Calculation
You are building three raised vegetable garden beds. Placed end-to-end, the total area is 20 feet long and 4 feet wide. You want to fill the boxes to a deep depth of 12 inches (1 foot).
- Convert depth to feet:
12 ÷ 12 = 1.0 feet - Calculate Cubic Feet:
20 ft × 4 ft × 1.0 ft = 80 cubic feet - Convert to Cubic Yards:
80 ÷ 27 = 2.96 cubic yards - Add 15% settling waste:
2.96 × 1.15 = 3.4 cubic yards
You should order 3.5 cubic yards of Garden Mix topsoil to perfectly fill the boxes.