Decomposed granite (DG) is a natural, finely textured material resulting from the weathering and erosion of solid granite rock. It provides a rustic aesthetic that blends seamlessly into various outdoor environments. DG is often favored as an alternative to traditional paving materials for creating usable outdoor space.
Defining the Material and Its Characteristics
Decomposed granite is characterized by fine particle size, ranging from a sand-like texture up to three-eighths of an inch in diameter. This grading allows the material to compact effectively, creating a firm surface. DG color is determined by the parent granite’s mineral composition, featuring tones like buff, gold, tan, gray, brown, and red.
The material possesses a good degree of permeability, allowing water to drain through it and reducing surface runoff. This property makes it a desirable choice for sustainable landscape design. Decomposed granite is available in two main forms: the loose or natural material, which is simply screened fines, and a stabilized version. Stabilized DG includes a binding agent, often a polymer, which enhances durability and minimizes erosion under foot traffic or weather.
Diverse Applications in Outdoor Design
The versatile nature of decomposed granite allows it to be used in numerous ways to define and enhance outdoor spaces. One of its most common applications is in the creation of pathways and garden walkways. For these areas, stabilized DG is often preferred because the binder helps the surface remain firm and resistant to displacement, ensuring a smooth and durable path that does not track easily.
Decomposed granite also functions effectively as a permeable alternative to concrete or pavers for patios and gathering areas. Its natural look provides a softer aesthetic underfoot for outdoor dining or lounging spaces. When used as a ground cover, particularly in xeriscaping or drought-tolerant gardens, loose DG is spread over large areas to suppress weed growth. This layer also helps the soil below retain moisture by reducing evaporation, which is a beneficial practice in arid regions.
For areas that must support heavier loads, such as residential driveways or parking spots, decomposed granite can be successfully implemented. However, for vehicular traffic, stabilization and a robust sub-base preparation are requirements. The binding agent ensures the DG layer can withstand the shearing forces of tires and the weight of vehicles without rutting or excessive material loss.
Essential Installation and Maintenance Practices
Successful use of decomposed granite depends on proper installation, starting with thorough sub-base preparation. The underlying soil must be graded for drainage and compacted to create a stable foundation. Edging is necessary, using materials like steel, wood, or stone, to contain the DG fines and prevent migration into surrounding areas.
After preparation, DG is spread evenly, typically several inches deep. This layer is moistened and compacted using a plate compactor or roller to achieve firmness. Compaction locks the fine particles together, creating a hard, usable surface, especially with stabilized versions. Maintenance is minimal, usually requiring only occasional spot-raking to redistribute shifted material or refill low spots.