Permanent rubbery mats are typically installed over concrete or asphalt as a foundation. Loose fill, like wood chips or gravel, however, should never be installed on concrete or asphalt.
The Consumer Product Safety Commission has worked with the American Society for Testing and Materials to produce detailed guidelines for playground surface depths as well as equipment safety. Call the CPSC hotline, 800-638-2772, to request its Handbook for Public Playground Safety. Other sources of playground safety advice are the American Academy of Orthopaedic Surgeons (800-824-BONES or www.AAOS.org).
It's What's Underneath That Counts
The number one safety measure playgrounds need—but the majority lack—is a shock-absorbing surface under the equipment. No matter how well you supervise your child and how well the equipment is designed with safety in mind, occasional falls are inevitable. In fact, of the approximately 200,000 children treated in emergency rooms each year for playground injuries, about three-fourths were hurt in falls to the ground or onto other equipment. Falls often result in broken bones. Most serious are those falls that result in head injury.
Equipment with asphalt or concrete underneath can lead to serious head injuries if a child falls. Grass or dirt, while a little softer, can become hard-packed and dangerous, too. The safest alternates are loose-fill materials or cushioning mats. While these surfaces can't totally protect a child from getting hurt, they can reduce the severity of the injury.
The height of the play equipment determines how deep the loose fill underneath should be. Children falling from greater heights need more cushion in a fall. The CPSC-recommended depth is at least 12 inches for equipment in typical public playgrounds. If your backyard equipment is not as tall, you won't need it quite as deep. Detailed information on depth needed for the height of specific equipment is available from CPSC.
Some playgrounds have soft surfaces but they don't cover a wide enough area. The soft surface, or “fall zone,” under a swing, for example, should extend out twice as far as the height of the swing in both the front and the back. The “fall zone” under stationary equipment should extend at least six feet in all directions from the edges of the equipment.
If loose fill material is used, it must be maintained. This includes replacing the material as needed and raking, leveling, and sifting to maintain an adequate depth and to remove foreign matter. Good drainage underneath the fill is necessary to maintain the surface.
Tales from the Safety Zone
The Iowa-based National Program for Playground Safety issued a report in 1999 rating America's public playgrounds, and it gave them an average grade of C-minus. In the 31 states where playgrounds were studied, Delaware earned the highest rating—a B—and Michigan and Florida were worst with D-minuses. The researchers found that soft materials under the equipment was not applied to the right areas in 62 percent of playgrounds and wasn't deep enough in 56 percent of the cases, even though the CPSC guidelines have been in place since 1981.
Mulch and Chips
Shredded mulch and wood chips are popular loose fill surface materials because they are easy to obtain, easy to install, and inexpensive. A retaining barrier is required to contain the material, and the loose fill has to be replenished often because it decomposes and compacts. The disadvantage is that it is subject to microbial growth when it's wet. It also can conceal sharp objects such as broken glass.
Sand and Pea Gravel
Sand and pea gravel also are inexpensive and easy to install. Maintenance is required similar to mulch and wood chips. Disadvantages of sand are that it can blow into children's eyes and can become hard-packed when wet. Kids also can track it out of the intended area, making regular replacement necessary, and of course there's the danger of it being used as a litter box by cats and other animals. Gravel can be hard to walk on. If it gets thrown onto walkways, it can cause falls.
Mats and Tiles
Rubbery mats and tiles come in a variety of synthetic materials and require little maintenance. They don't hide sharp objects or animal waste as loose fill can. The disadvantage is that mats cost a lot more initially and require professional installation.