Gravel is a versatile, inexpensive material used for a variety of landscaping purposes. Crushed gravel and pea gravel are two of the most commonly used kinds. Both are simple to work with but are best used in differed ways. Whether you're installing a patio or walkway over a bed of gravel, or mulching a sloped area, understand the differences to ensure stability and longevity of your landscaping.
The major difference between crushed and pea gravel is the shape. Crushed gravel is broken up pieces of rocks and recycled concrete. The pieces are irregularly shaped and range from 1/2 inch to 1 inch. The process of crushing the material reduces some pieces to a sand-like material that helps stabilise the gravel. Pea gravel is smooth, rounded rocks that measure 1/8 inch to 1 1/4 inches in diameter. Pea gravel is sourced from riverbeds and streams and is typically light brown, white or translucent.
Crushed Gravel Applications
For practical reasons, crushed rock is generally used below ground. The irregular shapes and sharp edges of crushed gravel allows the material to compact together snugly when tamped with a hand tamper or compactor machine. The result forms a hard base strong enough to support fence posts and the surfaces of driveways, walkways and patios. It's also flexible enough to allow underground water to drain and absorb tension to prevent frost heave damage. Decomposed granite is an exception as it is often used to pave walkways and driveways. The sand-like materials mixed with small pieces of granite soften the surface. Decomposed granite is applied loose or with a resin on top that joins the pieces into a solid surface.
Pea Gravel Applications
Unlike crushed gravel, pea gravel does not stabilise when compacted. Due to its smooth, round shape, pea gravel is not a good choice for a foundation because the rocks never settle. Above ground, pea gravel offers subtle texture as inorganic mulch. While pea gravel does not add nutrients to soil, it doesn't float away in heavy rains like large nuggets of bark mulch. Pea gravel is also used as backfill to reinforce stone and paver edging and spread over crushed gravel for a casual path as the smooth surface is comfortable beneath bare feet.
Both crushed and pea gravel are typically used because they are easy to work with and low maintenance. While pea gravel offers a water-penetrable surface and blocks weeds, its unstable nature means the rocks easily scatter. You must edge a pea gravel path to contain the pieces. Once installed as a base, crushed gravel should only require maintenance if the compacted layer is not thick enough to support the weight load of the surface. For instance, a walkway and patio calls for a 4- to 6-inch layer, but driveways require at least 8 inches.