When planning a gardening or landscaping project, loam is often the preferred soil choice because it promotes robust plant growth. Loam is an optimal soil blend that balances essential properties like drainage, aeration, and moisture retention. Accurately determining the volume of loam needed prevents material shortages and unnecessary expense. This calculation requires careful measurement of your project space and an understanding of the units in which loam is sold.
Understanding Loam: Composition and Ideal Characteristics
Loam is a specific type of soil defined by its textural classification, consisting of a balanced mix of sand, silt, and clay particles. This composition is generally considered the best medium for supporting the majority of plant life. An ideal loam texture often approaches a 40% sand, 40% silt, and 20% clay concentration.
The larger sand particles create air pockets that promote excellent drainage and prevent waterlogging. Medium-sized silt particles help retain moisture and nutrients more effectively than sand alone. Fine clay particles bind to positively charged nutrients like calcium and potassium, making them available to plants. This blend allows loam to hold water for absorption while still allowing excess water to drain away, fostering strong root development.
Establishing Project Needs: Area and Required Depth
The first step in calculating your loam requirement is accurately measuring the dimensions of the project area in feet. For rectangular spaces, determine the length and width. If the space is irregularly shaped, divide it into smaller, measurable sections and calculate the area of each before combining the totals.
The required depth of the loam layer varies significantly based on the intended purpose of the soil.
Depth Requirements
- Topdressing an existing lawn: 2 to 4 inches.
- Building a new lawn: 4 to 6 inches to support deep grass roots.
- Vegetable gardens or raised beds: 12 to 18 inches for maximum root growth.
- Trees and shrubs: 12 to 24 inches for anchorage and nutrient access.
Calculating Total Volume and Ordering Units
Once you have the area dimensions and the desired depth, calculate the total volume of loam needed. Ensure all three measurements (length, width, and depth) are in feet before performing the multiplication (Length x Width x Depth). If the depth was measured in inches, convert it to feet by dividing the number of inches by 12 (e.g., 6 inches = 0.5 feet).
The resulting volume will be in cubic feet. Since loam is commercially sold by the cubic yard, divide your total cubic footage by 27 to determine the number of cubic yards to order. One cubic yard is equivalent to 27 cubic feet.
Adjusting for Settling and Wastage
The calculated volume represents the theoretical amount of loose material required, but it does not account for settling after delivery and spreading. Loam naturally settles and compacts once exposed to moisture and gravity, meaning the final depth will be less than the initial volume ordered.
To ensure you achieve the target depth, add a buffer to your final calculated volume. Landscaping professionals advise adding an extra 10% to 15% to the calculated cubic yardage to account for compaction and minor wastage. Rounding up to the nearest whole or half cubic yard is recommended.