Installing artificial grass requires more than simply choosing the turf material itself. The performance, appearance, and longevity of the synthetic lawn depend entirely on the materials placed underneath. These layers form the structural foundation that manages water flow, prevents settling, and provides a smooth surface for the synthetic fibers. A properly constructed base ensures the turf remains stable and drains effectively over many years.
The foundation beneath artificial grass is a multi-layered system designed to provide stability and functionality. Without this carefully prepared understructure, issues like pooling water, uneven surfaces, and premature wear can quickly compromise the installation. Understanding the role of each layer is important for ensuring a durable and aesthetically pleasing result.
Preparing the Subgrade and Initial Drainage
The first step in creating a lasting artificial lawn is preparing the native soil, known as the subgrade. This process begins with excavation, which involves removing all existing organic material, such as sod, roots, and topsoil, typically four to six inches deep, to make room for the new base layers. Removing this organic matter prevents future decomposition, which would otherwise lead to uneven settling and dips in the finished surface.
After excavation, the subgrade must be compacted to prevent shifting and settling once the base materials are installed. Using a plate compactor ensures the soil is dense and stable, providing a firm foundation. Failure to compact the subgrade adequately can result in a wavy, unstable surface over time.
Establishing the correct grade, or slope, for water runoff is also important. Even though artificial turf drains vertically, the base materials must be sloped slightly, usually at a minimum of one to two percent. This slight incline directs rainwater away from structures and prevents water from pooling within the base layers, which can lead to odor issues or premature degradation. Setting the proper slope at this stage guarantees effective drainage, as subsequent layers will follow the contour of the prepared subgrade.
Selecting the Structural Base Material
The bulk of the artificial grass foundation is the structural base layer, which must provide both stability and permeability. This layer is typically composed of angular crushed aggregate material, which locks together when compacted to form a strong, load-bearing surface. Suitable materials include Class II road base, crushed limestone, or crushed granite, generally installed at a depth of three to four inches.
The angular shape of the crushed rock is superior to rounded river rock or pea gravel because it achieves a much higher level of compaction and structural integrity. The material is often specified as “3/4-inch minus,” meaning the particles range from three-quarters of an inch down to fine dust. This mixture of sizes allows the smaller particles to fill the voids between the larger stones, resulting in a dense, solid layer that resists shifting.
Decomposed granite (DG) is another popular choice for the structural base, particularly in drier climates. DG is a fine aggregate that compacts exceptionally well, creating a very stable surface. While it provides excellent stability, it may not drain as quickly as a coarser crushed stone blend in regions with heavy rainfall. The entire structural layer must be dampened and compacted to achieve 90 to 95 percent relative compaction, ensuring a permanent foundation.
The Essential Finishing Layers
The layers placed directly beneath the turf serve specific functions related to weed suppression and surface smoothness. The first is a geotextile fabric, often referred to as a weed barrier, which is unrolled over the compacted structural base. This woven or non-woven material prevents native weeds and organic growth from pushing up through the base and into the turf backing.
The geotextile fabric also stabilizes the base by distributing weight more evenly across the surface, helping to prevent minor depressions or shifting. It is important to use a permeable geotextile rather than a non-permeable material to ensure water can freely pass through to the drainage layers below. While it is often called a weed barrier, its primary purpose is to provide separation and stability between the base and the final surface layer.
The final material applied is a thin layer of fine aggregate, sometimes called quarry dust or stone dust, spread over the geotextile fabric. This layer is usually only about one-half to one inch deep and consists of very fine material like decomposed granite fines or rock dust. The purpose of this fine material is to create a perfectly smooth, non-abrasive surface directly beneath the artificial turf backing.
The fine aggregate layer handles the final, precise contouring and eliminates any minor inconsistencies left by the coarser structural base. This final layer is lightly compacted and leveled to ensure that the turf lays flat without dips or bumps, maximizing its aesthetic appeal and functional performance.