New Shock Pad Guidance Offers Insight Into Selection and Maintenance Process
By Dan Bond, CAE
With the rise in shock pad usage in synthetic turf sports field systems in North America, the Synthetic Turf Council (STC), the world’s largest organization dedicated solely to the synthetic turf industry, released the new Performance and Quality Guidelines for Shock Pads. These guidelines provide sports field managers, field specifiers and facility owners with objective measures when specifying a shock pad and comparing the minimum performance and durability of different shock pads.
These guidelines were drafted to compare the performance of different shock pads in an objective way, and, if appropriate, to allow the selection of a shock pad for a specific application. The document also specifies the minimum durability criteria to ensure that when a shock pad is incorporated into a synthetic turf system it will perform adequately for at least two lifecycles of the synthetic turf carpet. In having a shock pad incorporated into the synthetic turf systems, field managers should also ask about shock pads that have long warranties and can be recycled at the end of their useful life.
Shock pads typically come in two varieties. Pre-fabricated pads are factory made from foams, rubber or plastics and are transported to the field to be installed on a prepared field base. Insitu shock pads (also commonly referred to as elastic layers) are mixed onsite from a blend of binders (normally polyurethane) and elastomeric granules (normally recycled tire granulate). They are laid with a paving machine onto the prepared base. Shock pads typically range from 5/16 inch to 1.5 inches in depth, and are placed between the turf surface and stone base. For short pile carpets, the shock pad is typically laid on an asphalt base. In this guidance document, the STC encourages manufacturers of shock pads to have their products tested using the methods detailed, and include for certain properties minimum suggested guideline requirements.
The principal objective of a shock pad is to provide a permanent shock-absorbing layer within the synthetic turf system, which provides a minimum level of impact protection to athletes running and falling onto the surface, irrespective of the type of synthetic turf laid over the shock pad, or its condition. For sports where a true ball rebound is important (e.g. soccer, field hockey, tennis, etc.), a shock pad can also assist with controlling how the ball bounces. For short pile carpets, the shock pad can be a key contributor to providing impact attenuation (which is the measure of the shock-absorbing properties).
As performance testing for turf athletic fields has become more robust, shock pad usage has gained in popularity across North America. Shock pads are designed to assist in providing the sports performance and player protection properties that are required for the sport and athlete on the playing surface. They also aid the retention of these properties through the life of the playing surface.
In the goal of maintaining safe and durable playing surfaces, sports field managers are finding that installing a shock pad can supplement an overall maintenance program. However, it is important to note that shock pads do not replace the need for a maintenance program. For example, a shock pad can reduce the amount of infill compaction on the field, so the frequency between decompactions can be extended. For managers who choose a shock pad, many find that it provides uniform resilience, in addition to the resilience provided by the type of infill used in the synthetic turf system.
One of the challenges facing field managers is infill migration (when the infill within the synthetic turf system moves out of the system over time). There are many causes of infill migration, including heavily used fields, certain types of sports, turf fibre, pile height and even Mother Nature. On fields where infill migration frequently occurs, especially in high-traffic areas, the use of a shock pad can help achieve performance metrics. Additionally, for field managers who are looking at ways to reduce the amount of infill (and subsequent infill “splash” and migration from the field), a shock pad combined with lowering the height of the fibre pile and increasing the density of the pile itself can be an answer.
A number of different ways of measuring the impact attenuation properties of synthetic turf sports surfaces have been developed around the world. The international sports governing bodies for a number of sports have participated in the development of these test methods, have standardized on one procedure (ASTM F3189), and have incorporated them into their standards and regulations. The most commonly used test methods and standards have been incorporated into this guidance document, including from ASTM International and the international sports federations (FIFA, International Hockey Federation and World Rugby) and the STC.
It is very important for field managers to consider that a shock pad forms part of the synthetic turf sports surfacing system, and it is the performance of the total system that influences the athlete’s perception of a sports field. It also determines if it is providing the required levels of player protection and sports performance. Due to the different types of synthetic turf on the market, ranging from long pile (typically 1.5 inches to 2.5 inches) infilled surfaces that are typically used for football, soccer and rugby, to non-filled short pile surfaces (typically 0.5 inches) used for field hockey, there are many different shock pads, with differing performance characteristics available.
Some shock pads also offer multi-functional properties that are designed to assist in field performance. These include providing horizontal drainage and structural stability to the base, in a similar way to a paved asphalt layer. Poor drainage below the shock pad can cause pooling on the field, especially after heavy rainfall, or it can saturate and weaken the supporting materials in the aggregate base and subgrade. If you have questions, we recommend that you consult your field designer to determine whether a multi-functional shock pad is appropriate for your field. The STC maintains a list of field designers and architects in the STC Member Directory.
Other products, such as drainage cells, that are used in the construction of a synthetic turf field may also provide some characteristics of a shock pad. To meet the STC definition of a shock pad, however, these products should perform in accordance with the recommendations of these guidelines.
Dan Bond, CAE, is president and CEO of the Synthetic Turf Council (STC). Visit the STC website (https://www.syntheticturfcouncil.org) under the “Resources” tab to review the new shock pad performance guidelines.
Other STC Guidance Documents Available
STC offers other technical guidance documents that can aid sports field managers in the maintenance of turf fields. Technical guidelines include topics such as maintenance of infilled sports field, turf performance, guidelines for infilled fields, minimizing heat, turf performance and recycling/reusing/repurposing next stage turf. All are available on the STC website (http://www.syntheticturfcouncil.org) under the “Resources” tab.
Guidelines for Maintenance of Infilled Synthetic Turf Sports Fields
Also available in Spanish, these voluntary guidelines provide owners with objective maintenance guidance to augment, and not replace, the maintenance requirements and procedures of the company or companies providing the warranty for the field and the installation.
Guidelines for Synthetic Turf Performance
Also available in Spanish, these guidelines encourage periodic and voluntary testing to indicate the type of maintenance that should be implemented to maximize multi-purpose sports field performance. If a field is not performing within the desired range in critical test areas despite targeted maintenance, then the owner will know it may soon need to be replaced.
Suggested Environmental Guidelines for Infill
The purpose of these suggested voluntary guidelines is to provide owners, buyers and interested stakeholders an additional resource to better understand the environmental and toxicological considerations when evaluating the use of infill materials.
Guidelines for Crumb Rubber Infill Used in Synthetic Turf Fields
The purpose of this document is to provide producers, customers and the public with an understanding of what crumb rubber infill (CRI) is and how the industry manages its safety, purity and quality.
Guidelines for Minimizing the Risk of Heat-Related Illness
On a hot, sunny day, in addition to taking proper precautions to minimize their risk of heat exhaustion, heat stroke or other heat-related health complications regardless of the playing surface, those who play on synthetic turf should consider the practical risk avoidance strategies recommended in this STC guidance document.
Guideline to Recycle, Reuse, Repurpose, and Remove Synthetic Turf Systems
The goal of this document is to help the reader better understand the range of processes for identifying and managing the removal and disposition of a synthetic turf system once it may have reached the next stage of its useful life.