The makeup of the components and the elements to be included, or not to be included, in a synthetic turf system are determined by the design, use and expected performance of the system.
Typically, the fiber used in synthetic turf is textured and/or non-textured polypropylene, polyester, polyethylene, nylon or other suitable performing hybrid or copolymer in tape form or monofilament.
Synthetic turf types: There are several different types of synthetic turf available. Differentiated by construction are the tufted or the knitted synthetic turf systems. Both systems are comprised of synthetic fibers with primary and secondary backing systems and a resilient shock-absorbing system. The shock-absorbing system can consist of infill, a padding system, or a combination of both.
Fiber: Typically, the fiber used in synthetic turf is textured and/or non-textured polypropylene, polyester, polyethylene, nylon or other suitable performing hybrid or copolymer in tape form or monofilament. Fibers should be compliant to ASTM guidelines for total lead content.
Perforations: Depending on the final construction of the turf system, the system may or may not be permeable to water. Perforations are typically required of fully coated system backings to provide adequate vertical drainage throughout the system.
Quality control: The synthetic turf systems builder’s quality control program should be evaluated with the system.
Warranty: All of the proposed warranty documents should be obtained and the content thoroughly reviewed to ensure adequate coverage is contained therein.
There may be blanket warranty coverage, or each party – vendor, supplier, manufacturer, installation and maintenance contractor – may provide separate and limited coverage that should be clearly defined. It should also be clear exactly who covers what, with special attention given to the coverage of the turf fiber as it relates to possible damage during the tufting, coating, installation and maintenance processes.
Maintenance: Maintaining a synthetic turf field is essential for optimum appearance, safety, playing performance and field longevity. A regular schedule of maintenance should include surface cleaning; debris removal; grooming; and infill replenishment, redistribution and decompaction. The maintenance procedures and equipment, as specified by the synthetic turf system builder and required for the system, should be evaluated during the selection process so the appropriate budget resources for manpower and equipment may be allocated.
Other considerations: The synthetic turf systems builder, without liability or legal responsibility for the base (unless the base is part of their scope of work), should perform an inspection of the field planarity base on to which the synthetic turf system is to be installed, and to examine the finished surface for required compaction, water permeability and grade tolerances. After any discrepancies between the required materials, application and tolerance requirements noted have been corrected, the owner’s representative (architect/engineer) should review and approve for compliance with documents. The acceptance of the base construction should be included in the certification for warranty validation.
Evaluation of system components
Drainage system: An efficient and effective underground drainage system is an integral component of a synthetic turf system, and is designed to carry away the water that percolates through the turf. The system chosen will depend on the use of the field, climate, amount of rainfall and other factors.
Components: The drainage system may include the synthetic turf, pad, base materials and collector pipes that collect and remove stormwater from the playing field. The design of the drainage system is dependent upon local conditions, climates and site constraints.
Drainage: The expected performance evaluation and the systems used should undergo an independent engineering analysis.
Base materials: The aggregate base on which the synthetic turf is installed provides a structurally sound foundation for field construction and a media for drainage of the field. The base materials are critical to the performance of the entire system and should contain the necessary components and characteristics to satisfy local conditions. A good geotechnical report will provide essential information for a firm and stable base for the synthetic turf. A base that is properly designed and constructed should give the owner several years of use and last through several turf replacements. The use of design professionals and builders with demonstrated expertise and success in the development of synthetic turf systems is highly recommended.
Shock-absorbing resilient underlayment systems: The shock-absorbing elements, as part of the overall synthetic turf system, should meet or exceed the performance of the design and specification.
In situ cushion layer (elastic layer pad): If included in the design, these cushion systems should be installed in place with specialized paving equipment.
Prefabricated cushion layers (pad): If included in the design, these cushion layers are a manufactured product comprised of rolls or tiles of resilient material installed under and occasionally adhered to the synthetic turf backing.
Infill materials: Infill materials are comprised of rubber, sand, elastomers, organics and/or other suitable materials or combinations thereof that are placed on top of the synthetic turf backing system and between the synthetic surface fibers. This is needed for resiliency as well as structural integrity and directional stability.
Field use demands must be considered when selecting a synthetic turf system.
Irrigation system introduction: The installation of a manual or automatic irrigation system can be considered for synthetic turf installations. Guidelines on whether synthetic fields are watered are determined by factors such as region, climate, turf material, player traffic type and level of games played. High field temperatures can prove challenging to players throughout warmer climates. Watering enables the field to be cooled. Field cleansing and sanitation can be improved with watering from an irrigation system, particularly in climates that experience very little rainfall for natural cleansing.
The synthetic turf system and all of its components should be resistant to moisture, rot, mildew, bacteria, fungus growth, ultraviolet ray degradation at all field locations, and meet local code and environmental requirements.
Construction and installation
Inspection: Synthetic materials should be inspected prior to installation for:
- damaged or defective goods
- missing goods or quantities
- correct fiber type
- correct turf pile height and weight
- proper tuft bind
- correct backing perforation diameter and spacing, if applicable
- materials out of tolerance with the specification
Subgrade preparation: The subgrade should provide a stabilized foundation upon which base materials and subsequent components of playing field systems will be installed.
Function: It should also provide the pitched surface on which stormwater is directed toward the active drainage system for evacuation.
Shape and compaction: Prior to placement of base materials, the subgrade should be shaped to an appropriate profile and compacted by proof rolling to obtain a firm, even surface. Compaction should be performed to achieve a minimum of 95 percent in accordance with ASTM D698 Standard Proctor Method. The appropriate moisture content must be maintained in the field subgrade to allow for optimal levels of compaction.
Subgrade (rough) planarity: The tolerances for the finished subgrade should not exceed .5 inch as measured by a 10-foot straightedge (13 millimeters in 3 meters). The use of laser-guided and controlled equipment is highly recommended for subgrade preparation.
Aggregate: Installation of the aggregate base should provide a close, evenly textured surface meeting the required tolerances.
The use of laser-guided and controlled equipment is highly recommended for subgrade preparation.
PHOTOS COURTESY OF THE SYNTHETIC TURF COUNCIL.
Construction: Extreme care should be taken to ensure that there is no disturbance to the subgrade and that there is no displacement of the soil separator.
Finish-grade planarity (surface tolerances): The use of laser-guided and controlled equipment is highly recommended for subgrade preparation. The local deviation of the finished surface of the base stone should not exceed .25 inch in any direction when measured beneath a 10-foot-long straightedge (6 millimeters in 3 meters).
Synthetic turf material production quality assurance/quality control: Testing of materials should be performed prior to shipment of product to the job site to avoid additional costs or delay. Testing to be conducted should be a provision in the agreement between the parties and may include pile composition, pile weight, total weight, pile height, tuft bind (without infill) and grab/tear strength.
Synthetic turf installation: All synthetic turf systems should be installed to provide stability that will prevent panels from shifting or bunching.
Seaming method: The synthetic turf panels should be securely fastened together for the warranted life of the system. These seams are typically glued or sewn, the method for which varies from system to system. Specialized synthetic turf systems that are periodically removed and replaced may have seams that are comprised of Velcro or other easily attachable materials. For tufted infill systems the gap between the fibers should not exceed the gauge of the tufting. For other synthetic turf systems the seam gaps should not exceed 1/16 inch (2 millimeters).
Edge anchoring: The anchor may consist of a concrete curb, a treated wood header, a composite material or a trench drain.
Inlaid lines and markings: For tufted systems, the gap between the fibers should not exceed the gauge of the tufting.
Temperature: The carpet should never be rolled or unrolled when frozen, which can cause cracking and irreparable damage to the secondary backing.
Infill material installation: Correct installation is critical to performance of these systems and should follow the manufacturer’s recommendations.
Environmental conditions: It is recommended that infill materials should be installed under dry field conditions.
Method of application: The equipment used for the application of the infill materials should erect the fiber, place the infill materials, and should incorporate a metering method to provide consistent distribution. The equipment utilized should not distort or displace any base materials or damage the system in any way.
G-max testing: G-max testing should always be performed by an independent testing company or lab.
It is recommended that a minimum schedule for ongoing testing be included and understood by the parties to be at least at the end of year one and at the end of year three. Testing thereafter is at the owner’s option. The G-max should be tested in accordance with the above schedule.
The synthetic turf industry is continuously improving the quality, performance, sustainability, and durability of its sports field systems. The Synthetic Turf Council (STC) provides free access to reliable and up-to-date guidance and tools for the selection, installation, maintenance, and testing of these systems on its website: www.syntheticturfcouncil.org.
These technical resources include:
- Suggested Guidelines for the Essential Elements of Synthetic Turf Systems, revised November 2011
- STC Guideline for Synthetic Turf Performance, published December 2011
- STC Guidelines for Crumb Rubber Infill Used in Synthetic Turf Fields, published October 2011
- Suggested Guidelines for the Maintenance of Infilled Synthetic Turf Surfaces, published April 2007
- Glossary of Terms for Synthetic Turf, published November 2011
The STC encourages field owners to engage the services of a design professional with proven synthetic turf experience. An experienced consultant can provide consulting, engineering and landscape architecture services that include master planning, design, budgeting, document preparation, permitting and on-site construction services.
The preceeding is excerpted from the Synthetic Turf Council’s Suggested Guidelines for the Essential Elements of Synthetic Turf Systems, revised November 2011. The full document, in addition to providing expanded guidance, also includes test protocols and typical reference specifications. Suggested Guidelines for the Essential Elements of Synthetic Turf Systems, revised 11/11
Rick Doyle is president of the Synthetic Turf Council.