The quality of an artificial turf installation depends entirely on the preparation and materials placed underneath the turf itself. Synthetic turf requires a robust, engineered foundation to maintain its appearance and function. This base provides the necessary stability to prevent sinking or shifting, and the permeability required for efficient water drainage. A properly constructed base layer ensures longevity by allowing rainwater to filter through quickly and preventing uneven settling.
Preparation of the Existing Ground
The initial step involves removing all existing organic material by excavating the area to a specified depth. Homeowners should remove existing grass, roots, and debris down to approximately two to four inches. This depth accommodates the new sub-base materials and maintains the desired finished height of the turf surface. Organic matter, if left in place, will decompose over time, leading to voids and uneven settling beneath the new lawn.
Once the area is cleared, the native soil remaining must be properly graded. This involves creating a slight slope, usually around two percent, to direct water away from nearby structures or property lines. Compacting this native soil layer with a plate compactor stabilizes the ground before any new material is introduced. This prevents the underlying earth from shifting or settling, which maintains the integrity of the entire system.
The Essential Sub-Base Layer
Directly on top of the compacted native soil, a structural sub-base layer is placed, serving as the primary support and drainage mechanism. This layer uses crushed aggregate materials chosen for their angular shape and ability to drain freely. Common choices include Class II Road Base, decomposed granite, or a “3/8-inch minus” blend. The angularity of these materials allows them to interlock tightly when compacted, providing superior stability.
This sub-base should be installed three to four inches thick for most residential applications. The material is spread evenly and thoroughly wetted before being compacted with a heavy plate compactor. Achieving a high compaction density, often specified around 90 percent, may require applying the material in multiple two-inch lifts. This layering creates a dense, rock-hard foundation that will not sink under foot traffic or shift.
The porosity of this compacted aggregate layer allows rainwater to filter vertically and horizontally away from the surface. Without this sub-base, water would collect on the native soil, leading to hydrostatic pressure and poor drainage. This aggregate foundation provides the stability and permeability necessary for a durable, long-lasting surface.
Geotextile and Permeable Barriers
Permeable geotextile fabric provides separation and weed control. This non-woven, synthetic material allows water to pass through freely while preventing the migration of fine soil particles. It is most often placed directly over the compacted native soil before the aggregate sub-base is added. This acts as a barrier, preventing the sub-base material from sinking into the softer earth below.
A second layer of geotextile is sometimes placed over the compacted sub-base aggregate just before the turf is rolled out. This secondary placement serves as the primary weed barrier, blocking potential weed growth toward the turf backing. The geotextile physically inhibits plant roots while ensuring the drainage capabilities of the base layers remain uncompromised.
Permeable drainage mats are specialized barriers used in areas with clay soil or drainage issues. Placed directly beneath the turf, they feature a three-dimensional structure that creates an air gap. This structure allows water to flow rapidly across the area, enhancing the rate of water removal.
Optional Components and Edging
Several optional materials can be incorporated to enhance the installation. Edging materials are frequently installed around the perimeter to contain the aggregate base and provide a clean, finished line. Containment can be achieved using materials such as flexible plastic bender board, metal edging, or a concrete curb. The edging material is positioned flush with the final turf height, ensuring a smooth transition.
Shock-Absorbent Pads
For areas intended for children’s play or where additional cushioning is desired, a shock-absorbent pad can be placed directly on top of the compacted sub-base. These pads, often made from recycled foam or rubber, are designed to absorb impact and improve the fall height rating of the surface. While not necessary for structural stability, these layers increase comfort and safety.
Crushed Fines or Sand
A final, thin layer of crushed fines or fine-grade sand is often applied to the compacted sub-base just before the turf is installed. This material, such as granite dust, is used as a final screeding layer to smooth out minor imperfections. This fine layer ensures a uniform surface, preventing small bumps or divots from being visible through the turf.