Decomposed granite (DG) is a fine, granular material produced by the natural weathering of granite rock. This process breaks down the parent material into a mix of small, angular gravel pieces and a finer, sand-like component, giving it a distinctive texture. DG is a popular choice for landscaping projects due to its natural appearance and permeability, commonly used for creating patios, garden paths, and recreational areas.
Quick Answer Standard Coverage Rates
The coverage area of one cubic yard of decomposed granite depends entirely on the depth of application. One cubic yard is a fixed volume of 27 cubic feet. Landscaping projects often standardize on common depths to achieve proper stability and function. For a finished depth of 2 inches, one cubic yard of DG covers approximately 162 square feet, suitable for aesthetic applications or light-use pedestrian pathways. The 3-inch depth is often considered the minimum necessary for a stable pathway that handles regular foot traffic, covering about 108 square feet per yard.
Calculating Coverage for Specific Depths
For projects requiring a depth other than the common 2 or 3 inches, a precise calculation is necessary. The goal is to convert the desired depth from inches into feet to maintain consistent units. To perform this conversion, the depth in inches must be divided by 12. For example, 4 inches converts to 0.33 feet (4 divided by 12). Once the depth is in feet, the potential square footage coverage is found by dividing the total volume (27 cubic feet) by the depth in feet.
The mathematical formula is: Square Footage = 27 / (Depth in Inches / 12). If a project requires 1.5 inches, the calculation is 27 / (1.5 / 12), meaning one cubic yard covers 216 square feet.
How Compaction and Density Affect Volume
Real-world coverage will be slightly less than the mathematical calculation due to compaction. Compaction is the necessary process of mechanically pressing the material to increase density and create a firm, stable surface. During installation, DG is spread in thin layers and compacted, often achieving 88% to 95% of its maximum dry density. This process causes the loose volume to shrink, resulting in a 10% to 20% loss in volume. The final compacted depth is what matters for durability, requiring the initial uncompacted volume to be greater.
The initial moisture content also influences the DG’s density and ease of compaction. Material that is too dry will not compact effectively, while overly saturated material may become difficult to work with. Therefore, it is recommended practice to order approximately 10% more material than the pure volume calculation suggests to account for settling and minor waste during installation.
Required Depths Based on Project Type
The required depth of decomposed granite is determined by the intended use and the expected level of traffic. Different project types demand specific minimum depths to ensure long-term stability and resistance to rutting or erosion. A pedestrian pathway seeing light foot traffic can use a compacted depth of 2 to 3 inches, which provides a suitable walking surface. For high-traffic patios or areas where heavy furniture rests, a greater compacted depth of 3 to 4 inches is recommended to prevent shifting and depressions.
Projects involving heavier loads, such as driveways or areas designated for light vehicular traffic, require a robust foundation. These applications specify a compacted DG layer of at least 4 inches, often installed over a deeper base layer of road base material. Proper edging, such as metal or concrete borders, is also necessary for all applications to contain the DG and maintain the required depth.