A playground surface is whatever material lies under and around swings, slides, monkey bars, and other playground equipment.

Surfaces come in a broad variety of types, some more functional than others. Some meet national standards for safety and wheelchair accessibility; others do not (see table below). Playground surfaces also come in a broad range of prices, from about $2,000 to over $25,000 for an average-size playground (about 2,500 square feet).

The process of choosing a playground surface starts with determining a community's needs and resources. Some owner/operators may prefer the natural look of wood fibers, even if they have ample financial means; others may prefer more expensive poured rubber seamless surfaces that come in a wide range of colors. In all cases, surfaces should be certified by the International Play Equipment Manufacturers Association (IPEMA) to pass ASTM International standards for safety, purity, and wheelchair accessibility. Playground surface suppliers who have such certifications usually make them available to their customers.

Safety
Many sources state that playground-related injuries send 200,000 children to an emergency room every year. If visits to doctors are included, the figure rises to 500,000 injuries, according to the American Academy of Orthopedic Surgeons. More than half of these injuries result from falls to a playground surface, which can cause fractures, concussions, dislocations, and internal injuries. Recognizing these facts, many organizations, including the Consumer Product Safety Commission, have issued guidelines ("Public Playground Safety Checklist") and standards for playground surfaces. Nevertheless, there are still many facilities that do not meet these requirements.

Testing methods and standards
ASTM International has issued what it calls the "ASTM Standard Specification for Impact Attenuation of Surface Systems Under and Around Playground Equipment," which is known by its numerical designation, F1292. This standard accounts for both the deceleration of the head during impact and the length of time the head takes to stop moving. The test simulates the impact of a child's head hitting the surface from various heights of the playground equipment. Details available at ASTM.org.

Accessibility
A successful playground surface must be soft enough to cushion falls; it must also be firm enough to meet the requirements of the Americans With Disabilities Act (ADA), which means it must offer easy mobility for children in wheelchairs. Meeting these dual objectives limits the number of types of surfaces that can be considered by responsible playground owner/operators. ASTM International has developed test method F1951 to evaluate compliance with the Americans With Disability Act (ADA).

As the table makes clear, some surfaces commonly used do not provide adequate protection from the effects of falling, or may not offer adequate wheelchair access. The American Academy of Orthopedic Surgeons states, "Soil, packed dirt, grass, and turf are not recommended for surfacing." A thick layer of lush green grass, moist from recent rains, may seem soft enough. But in practice the grass wears away and either turns to mud in wet weather or dries to a hard crust in dry weather.

A Popular Solution
Judging by the number of installations, the most popular low-cost manufactured surface that meets national standards for safety and wheelchair accessibility is "engineered wood fiber." It is called "engineered," because the wood is mechanically shredded into sizes and aspect ratios determined by a series of specified sieves, through which the final product must pass. In addition, the finished product must meet ASTM International standard F2075, which tests for various properties, including size, particle aspect ratio, and the presence of toxic chemicals and tramp metal. In use, the wood fibers knit together to form a mat that is springy enough to meet ASTM F1292 for impact attenuation, yet firm enough to meet ASTM F1951 for wheelchair access.

Engineered wood fiber is made from biodegradable virgin wood, rather than used wood such as recycled pallets Used wood may contain staples and other foreign matter and should never be used for a playground surface. Engineered wood fiber should not be confused with wood chips or bark, which tend to be larger pieces of random shape. Engineered wood fiber is sometimes referred to as "mulch," but this is a misnomer, since, according to the Oxford American Dictionary, mulch is "a material (such as decaying leaves, bark, or compost) spread around or over a plant to enrich or insulate the soil."

Engineered wood fiber is available in a complete system that includes a geo-textile fabric to separate the soil from the wood fibers and a roll-out drainage system that assures a playable surface, even after a rain.

One reason for the popularity of engineered wood fiber is its low cost - $2.00 to $3.00 per square foot installed. (On a square-foot installed basis, shredded rubber costs $5.00 to $7.00; rubber tiles, $9.00 to $12.00; and poured-in-place (PIP) seamless rubber surfaces, $9.00 to $15.00.)

Despite its many advantages, engineered wood fiber does have certain issues. Since the material is loose, it can be scuffed away from the bottom of slides or under swings. (Special rubber wear mats are available to prevent this problem.) Also, a wood fiber surface tends to compact over time and needs to be topped off every two to three years, depending on how hard a playground is used.

Other Surfaces
Poured-in-place (PIP): is typically a one-piece, seamless EPDM rubber surface, usually about 3/8" thick, which is placed over a layer of cushioning from 1" to 5" inches deep, consisting of rubber particles bound together with a polyurethane binder. The surface comes in a wide range of colors and even mixtures of colors. Striking effects can be achieved, especially when the color is chosen to work with the colors of the play equipment or adjacent buildings. At considerable cost, this surface can also be configured as colorful designs. A typical poured-in-place playground surface meets national standards for safety and wheelchair accessibility.

On the downside, the sun's rays and power washing may cause PIP colors to fade and degrade after a few years. Contrary to common opinion, a PIP surface is not maintenance-free. Removing debris, such as soda caps, dirt, and cigarette butts, has to be factored into ongoing costs. Its longevity varies and is often a function of the installer's skill. But its main disadvantage is high cost, relative to engineered wood fiber.

ATP rubberized unitary surface. ATP stands for Aliphatic Thermoplastic Monomer. Based on new technology, this surface also meets safety and accessibility standards. It consists of a layer of almost-spherical rubber particles, about one-sixteenth of an inch in diameter, which are chemically bound by a color-fast binder. This surface, in turn, is bonded to a layer of Engineered Recycled Foam (ERF) to absorb shock. The colors are vibrant, and they will not fade from the sun or power washing. As with PIP, its main disadvantage is high cost. But this limitation is somewhat offset by long life: Data from Europe and the U.S. indicate these surfaces have a useful life of at least 10 years.

Shredded rubber. Finding alternate uses for used tires has become an increasing burden for many municipalities. One use is to shred the tires to a particle size of about 1" by 1/8" and then use the loose particles as a playground surface, which absorbs shock effectively and meets the ASTM F1292 standard.

But there are certain drawbacks. The material moves around in a playground as children play, creating an uneven surface that is not wheelchair accessible. Wear areas under swings and at the base of slides are particularly prone to scuffing out. When this occurs, the thickness of the shredded rubber surface may not be enough to cushion falls from originally specified heights. There is also a risk of fire. Only a small number of such fires are reported each year, but they are apt to be extremely hot and may not respond to conventional fire-fighting equipment. When this occurs, the playground equipment above the surface may be totally destroyed.

Sand and gravel: The extent to which these surfaces meet safety standards depends on the exact type and depth of the material used. When sand is wet, the surface becomes hard and unyielding (think of walking along the beach at the water line). In such a condition, the ability of a sand surface to absorb impact is seriously compromised. Neither sand nor pea gravel meet the requirements of the Americans With Disabilities Act for wheelchair accessibility. Based on these prohibitive limitations, authorities agree that sand and pea gravel should never be used as a safety surface in playgrounds.

Role of IPEMA
The International Play Equipment Manufacturers Association (IPEMA) provides a third-party certification service enabled by appointing a testing laboratory to determine if a particular surface conforms to ASTM standards F1292, F1951, and F2075. IPEMA's seal on a provider's document is clear evidence that the covered material has met these tests. Owner/operators should request a copy of this certification for their own protection. Note that some suppliers do not offer proof of certification and that mere membership in IPEMA does not mean that a particular supplier's material has been certified. A list of certified suppliers can be found on their website.