Artificial grass infill refers to the granular material, often a specialized sand or rubber, that is swept into the synthetic turf fibers after installation. Selecting the correct infill is a major decision that influences the long-term functionality, aesthetic quality, and performance characteristics of the finished landscape.
Why Artificial Grass Requires Infill
The primary mechanical purpose of infill is to provide necessary ballast to the turf system. Without this added weight, the synthetic grass is prone to shifting, wrinkling, or developing ripples, especially with temperature changes. The granular material anchors the entire sheet to the sub-base, maintaining a smooth, taut appearance.
Infill material fills the space between the synthetic grass fibers, offering structural support to keep the blades standing upright. This prevents the turf from matting down or flattening under foot traffic, which helps to preserve the intended aesthetic of the lawn. Furthermore, the infill layer acts as a buffer, shielding the turf’s polyurethane or latex backing from harmful ultraviolet (UV) radiation.
A correctly installed infill layer also plays a significant role in improving the surface’s permeability. The granular material assists in directing water down through the turf and into the prepared drainage layer below, preventing pooling on the surface. This layer also provides a slight cushioning effect, which contributes to a more comfortable feel underfoot than the bare turf alone.
Different Types of Infill Materials
Standard infill is silica sand, which is readily available and offers a cost-effective solution. The high density of silica provides excellent weight and stability to the turf, making it a reliable anchor against movement. However, silica sand can compact over time, potentially stiffening the surface and reducing its ability to support upright blades.
Another common option is crumb rubber, often derived from recycled tires. This material is favored for play areas and sports fields due to its superior shock absorption and padding characteristics, significantly reducing impact forces. Crumb rubber is lighter than sand but is known to retain and radiate substantial heat, making the turf surface noticeably hotter in direct sunlight.
To mitigate some of the drawbacks of silica, specialized coated sands have been developed, such as those treated with acrylic or TPE polymers. These coatings prevent the grains from breaking down or compacting, maintaining better drainage and a softer feel over time. The coating also often allows for coloring, which can reduce the reflectivity and heat absorption of the infill layer.
For applications involving pets, zeolite infill is often recommended due to its unique chemical properties. Zeolite is a natural mineral that acts as a molecular sieve, effectively capturing and neutralizing ammonia gases produced by pet urine. This odor-absorption capability makes it a preferred choice for kennels or backyard pet areas, though it is less dense and provides less ballast than silica sand.
Calculating, Installing, and Maintaining Infill
Calculation
The required quantity of infill is directly proportional to the turf’s pile height and the intended usage of the area. A general guideline suggests applying enough material to cover approximately 60% to 80% of the blade length. For common medium-pile turf, the requirement often falls between 1.5 to 2.5 pounds of infill per square foot. Short-pile turf, typically 1 inch or less, requires less infill, perhaps only 1 pound per square foot. Conversely, high-traffic areas or long-pile turf may require up to 4 pounds per square foot to ensure maximum blade support and stability.
Installation
The most effective way to install infill is by using a broadcast or drop spreader to ensure even material distribution. Applying the material in small batches prevents uneven coverage. The infill should be applied when the turf is dry, allowing the granules to flow freely down to the backing layer. Immediately after spreading, the infill must be worked down into the base of the turf fibers using a stiff-bristled broom or a power broom. This process, often called cross-brushing, involves brushing against the grain of the fibers to open them up and allow the infill to settle deeply.
Maintenance
Infill maintenance primarily involves periodic replenishment, as some material can be displaced through heavy use or natural movement over time. Turf owners should plan to “top-off” the infill layer every 12 to 18 months, applying a light coat to maintain the required depth and prevent the blades from matting. Regularly cross-brushing the turf will also help keep the existing infill level and prevent compaction in high-traffic zones.