The transformation of America's playgrounds has been slow and steady, influenced greatly by European playground design concepts. The greatest driving force, however, is concern for child safety. Industry guidelines now recommend different levels of surface thickness, depending on the "fall height" of playground equipment, which is essentially the maximum height from which a child could fall.

Meeting—or exceeding—the suggested guidelines should be a high priority because falls are the leading cause of injury on the playground. The statistics are staggering: As many as 70 percent of all injuries and 90 percent of serious injuries on the playground are related to falls, according to the U.S. Consumer Product Safety Commission (CPSC). Studies have shown that the risk of injury can be minimized by simply restricting height levels of playground equipment to age-appropriate levels and maintaining the appropriate thickness and shock absorption of surface materials.

On the playground, you initially get to choose between two types of surface: loose fill like wood chips, pea gravel, sand, shredded recycled rubber and other, similar materials; and unitary surfaces, which include poured-in-place surfaces and rubber tiles.

While the initial affordability of "loose-fill" options can be alluring, they can also pose some problems. They are more easily displaced, which can create a safety hazard, and thus require more frequent maintenance. In high-traffic areas like the slide runout and underneath swings, the surface can be displaced fairly quickly. This affects compliance with safety recommendations regarding surface thickness in relation to fall heights.