By Jerome Morningstar, Sof Surfaces

When specifying a safety surface, it is important to consider a system that provides ASTM F1292-04 test results that are a minimum of 20 percent better than the upper limit. By ensuring that your system performs 20 percent better, you are in effect building in a safety margin to compensate for future wear and tear on the surface. A surface producing results close to the upper limit is unlikely to remain in compliance over the long term.
Photos courtesy of Sof Surfaces

It is estimated that over 70 percent of playground injuries are due to falls to the surface. Unfortunately, and in spite of our best efforts, the very nature of children’s play makes falls to the surface inevitable. In light of this, protective surfacing options remain one of the most overlooked and under evaluated aspects of playground design.

Playground surfacing is as diverse as the equipment placed upon it. The many different types of surfacing available can be generally broken down into two main categories consisting of loose fill and unitary materials.

There are many loose fill materials in use today such as wood chips, pea stone, sand, bark mulch, rubber mulch and engineered wood fiber (EWF).

When shopping for a safety surface, the initial purchase price is an important consideration, but even more important is the actual cost of the surface projected over a period of years. More often than not, lower initial priced surfaces end up being the higher priced option in the long term due to extensive maintenance and replenishment costs.

The primary advantages associated with loose fill materials include the lower initial costs as well as the favorable initial impact attenuation ratings. The initial advantages however are limited by the generally high life cycle costs associated with regular maintenance and replenishment requirements needed to ensure that the surface remains in compliance with current safety standards.

The second category, unitary surfacing, consists of two major types of products including poured in place (PIP) and prefabricated mats or tiles.

Poured in place (PIP) surfacing is a dual density system consisting of a low density base course and a higher density top wear course. The poured in place system is mixed, leveled and finished on site by specially trained installation personnel representing the manufacturer.

The two key measurements are HIC (Head injury criteria) and GMAX, which is the measure of the maximum acceleration (shock) produced by an impact, both relating to the ability of the surfacing system to absorb impact or cushion falls. The standard allows for a maximum HIC reading of 1000 and a maximum GMAX reading of 200.

The second prevalent unitary surfacing option is prefabricated product supplied in a mat or tile form. These materials are generally made from a combination of recycled and virgin rubber combined with a polyurethane resin. Unlike poured in place that is field manufactured, this product is compression molded in a manufacturing environment prior to being shipped to the playground for installation.

Unitary surfacing offers many functional advantages including low maintenance and low life cycle costs. Since the material is unitary in nature, extensive maintenance is not required in order to maintain consistent fall protection and wheelchair mobility. Within the unitary category pre-manufactured product supplied in mat or tile form are seen to offer additional advantages involving cost consistency and durability.

In order to ensure that your surfacing product exceeds in the critical performance categories, the following questions should form an integral part of your product inquiry.

To ensure performance over the long term, it is important to look for a surface that has a minimum 10-year warranty to ASTM F1292-04 when tested on site. Mandating periodic field-testing is another way to monitor proper compliance.

1) Does the surface comply with current ADA standards?

One important component of an accessible playground is the surface. By default, most unitary surfaces automatically meet this requirement. Although some loose fill materials also meet the requirement, many others do not. Particular attention should be given to this requirement when investigating a loose fill option. Accessibility can be demonstrated by the manufacturer by supplying their test documents indicating compliance to ASTM F 1951.

2) Does the surface meet the latest standard for impact attenuation?

ASTM F1292-04 is the standard that applies to the impact absorbing properties of a playground surface. In a very general description, a hemispherical shaped head form is dropped onto the surfacing specimen which sends key measurements to a computer upon impact. The two key measurements are HIC (Head injury criteria) and GMAX, which is the measure of the maximum acceleration (shock) produced by an impact, both relating to the ability of the surfacing system to absorb impact or cushion falls. The standard allows for a maximum HIC reading of 1000 and a maximum GMAX reading of 200. In order for a surface to meet the standard, it must provide readings below these numbers at pre-specified heights and various temperatures.

Both categories of surfacing listed above should comply with the current standards provided they are installed to the manufacturer?EUR??,,????'???s specifications. Surfaces such a packed dirt, gravel and asphalt however do not meet the standard.

3) What test results did the surface achieve at the specified fall requirement?

Although ASTM F1292-04 states that a surface must perform under 1000 HIC and 200 Gmax, these readings are the maximum allowable limit. When purchasing a safety surface, it is important to consider a system that provides ASTM F1292-04 test results that are a minimum of 20 percent better than the upper limit. A surface producing results close to the upper limit is unlikely to remain in compliance over the long term. Every manufacturer should be able to provide you with a certified test report listing the ASTM F1292-04 results for their surfacing product.

4) How long is the surface guaranteed to meet the F1292-04 standard?

In addition to building in your safety margin as described above, it is important to carefully look at the warranty offered by the manufacturer. Test reports provided by the manufacturer are laboratory reports and do not necessarily take into consideration certain factors that may be unique to your site. It is very important to carefully evaluate the warranty. Some warranties are stated in very general terms when further analysis reveals that compliance to the F1292 standard is not covered.

5) How long is the surface guaranteed against defects in material and workmanship?

One of the biggest challenges for a surfacing manufacture is finding the balance between resilience and durability. The difficulty lies in manufacturing a product that is both soft enough to provide long term fall protection but also durable enough to withstand the wear and tear of typical playground use. To ensure that your surface has succeeded in meeting both requirements you should be looking for a minimum 10-year warranty against premature wear in addition to fall height compliance.