Rock gravel is an essential material for many landscaping projects. It consists of either stones or recycled concrete that is crushed down to different sizes. Rock gravel can be used to construct a foundation or as the surface for a casual patio or walkway. The best type of rock gravel to use depends on your project and the type of soil in your yard.
If you want to use gravel as inorganic mulch, pea gravel offers a soft, subtle backdrop. It ranges in size from 1/8 inch for small gravel and 1/2 inch for large. The rocks are round and smooth, and typically white, light brown or gray. You can also use pea gravel to backfill edging as a second barrier to wayward grass and weeds.
Decomposed granite is used to pave walkways, driveways and patios. This loose material is a mix of 1/4 inch stones and fine, sand-like powder. The material compacts to form a solid surface that doesn't scatter as easily as other types of gravel. The three main ways to pave with decomposed granite are to leave the material loose and tamp it, mix it with a stabilizer to decrease erosion, or coat it with a resin to join the stones into a hard surface.
Large, irregularly-shaped rock gravel is used to construct foundations for paved surfaces. The sharp edges allow these rocks to wedge together when you compact them with a machine or tamper. Compacted rocks enable water to drain through crevices while providing flexibility as the ground freezes and thaws, preventing frost heave surface damage. The typical size for foundation gravel is 3/4 inch.
River rocks are smooth and rounded like pea gravel, only larger in size and more expensive. They come polished or in a range of different colors. River rocks are a good choice if you are laying garden borders or spreading gravel over a secondary path. As a surface material, river rocks require a compacted foundation to prevent them from sinking, and edging to contain them.