Safety Surfacing Introduction

The protective playground surface is often the most overlooked element of backyard playground safety. While approximately 80% of public playgrounds have some form of shock-absorbing protective surfacing under playground equipment, only 9% of home backyard playgrounds do, according to a 2001 playground injury study conducted by the U.S. Consumer Products Safety Commission (CPSC). The study found that, of the approximately 50,000 injuries per year associated with home backyard playground equipment, 69% of the injuries were a result of falls to a non-protective surface below the equipment.

The most common backyard playground surface options are grass and dirt, but neither surface offers adequate protection against serious injury due to falls, even falls that occur from 30 inches or less above the ground. Fractures of the arms and hands, and lacerations and contusions of the head and face are the most commonly reported injuries that result from a child falling from playground equipment to a non-protective playground surface such as grass or dirt as reported by the CPSC.

The good news is that there are number of protective playground surface options for the backyard playground that will meet the need for playground safety. As you might expect, playground surface options range in cost from affordable to expensive, and each option has its own list advantages and disadvantages. Weighing the positive and negative qualities of each type of playground surface material, as presented in this article, should allow you to choose the most appropriate playground surface for your backyard playground.

Critical Height of Playground Equipment

The first and most vital piece of information to know when considering different options for your protective playground surface is critical height. Critical height refers to the “maximum fall height from which a life-threatening head injury would not be expected to occur.” The critical height of your playground equipment equals the height (in feet) of the uppermost portion of your backyard playground equipment that is accessible to children. The protective playground surface you choose for your backyard playground should be installed with a depth that is appropriate for your equipment’s critical height.

The following table shows the critical height (in feet) for each of the loose-fill surface materials described in this article “when tested in an uncompressed state at depths of 6, 9, and 12 inches. The table also shows the critical height when a 9 inch depth of each material was tested in a compressed state.”

Material	Uncompressed Depth			Compressed Depth
	6 Inch	9 Inch	12 Inch	9 Inch
Wood Chips*	7 ft	10 ft	11 ft	10 ft
Shredded Bark Mulch	6 ft	10 ft	11 ft	7 ft
Engineered Wood Fibers**	6 ft	7 ft	>12 ft	6 ft
Fine Sand	5 ft	5 ft	9 ft	5 ft
Course Sand	5 ft	5 ft	6 ft	4 ft
Fine Gravel	6 ft	7 ft	10 ft	6 ft
Medium Gravel	5 ft	5 ft	6 ft	5 ft
Shredded Tires***	10-12 ft	N/A	N/A	N/A

*	This product was referred to as Wood Mulch in previous versions of the handbook.  The term Wood Chips more accurately describes the product.
**	This product was referred to as Uniform Wood Chips in previous versions of the handbook.   In the playground industry, the product is more commonly known as Engineered Wood Fibers.
***	This data is from tests conducted by independent testing laboratories on a 6 inch depth of uncompressed shredded tire samples produced by four manufacturers.  The test results reported critical heights which varied from 10 feet to greater than 12 feet.  It is recommended that persons seeking to install shredded tires as a protective surface request test data from the supplier showing the critical heights of the material when it was tested in accordance with ASTM F1292.

If the critical height of your backyard playground equipment is 8 feet, then your choices, according to the table above, would be 9 inches of compressed or uncompressed wood chips, 9 inches of uncompressed shredded bark mulch, 12 inches of uncompressed play sand, 12 inches of uncompressed pea gravel, or 6 inches of uncompressed recycled rubber mulch. Understanding some of the advantages and disadvantages of loose-fill surface materials should assist you in narrowing the choices to meet your specific needs.

Alternatives to loose-fill surface materials are rubber playground tiles, rubber mats, and poured-in-place playground surfaces. These options are available from a number of manufacturers who may use a variety of shock-absorbing materials. The manufacturers should be able to provide you with test data that shows the critical height for the protective surfaces they offer.

Loose-Fill Playground Surface Options

In general, loose-fill playground surface materials like wood chips, shredded bark mulch, pea gravel, play sand, and recycled rubber mulch are the most common choices for backyard playgrounds because they are affordable and easy to obtain from a local garden center or home improvement warehouse. Recycled rubber mulch can also be found in a variety of colors and sizes through internet suppliers.

Common Characteristics of Loose-Fill Playground Surface Materials

GENERAL:

• A retaining barrier of some kind is required to prevent the surface materials from becoming displaced due to active play or weather conditions.
• Loose-fill materials should never be installed on top of hard surfaces like concrete or asphalt.
• Good drainage beneath the protective surface is necessary.

ADVANTAGE:

• The initial cost of installing a loose-fill playground surface under your backyard playground equipment is generally low because the materials are easy to find and are relatively inexpensive.

DISADVANTAGES:

• Over time, loose-fill materials can become compressed, thus decreasing their protective abilities.
• Recommended depths can be compromised when active play or windy conditions displace the loose-fill materials.
• Debris such as broken glass, nails, and other sharp objects which can cause injury can be easily hidden by loose-fill materials.
• Continuous maintenance is required to maintain proper depth and to remove debris. Maintenance can include raking, sifting, grading, and leveling.
• Periodic renewal or replacement of loose-fill materials is necessary, which can be time consuming and costly. The exception to this is recycled rubber mulches – see below for more detail.

Wood Chips and Shredded bark mulch

ADVANTAGES:

• Wood chips and shredded bark mulch are less abrasive than play sand.
• Animals are less likely to foul wood chips and shredded bark mulch.
• Wood chips and shredded bark mulch are attractive.

DISADVANTAGES:

• The protective ability of wood chips and shredded bark mulch is reduced in rainy, humid, and freezing weather conditions.
• Over time, wood chips and shredded bark mulch will become pulverized, compacted, and will decompose.
• Wood chips and shredded bark mulch can develop fungus and mold when wet.
• Insects are attracted to wood chips and shredded bark mulch.

Pea Gravel

ADVANTAGES:

• Pea gravel will not pulverize and decompose.
• Mold and fungus growth is not generally an issue.
• Animals and insects are less attracted to pea gravel.

DISADVANTAGES:

• Pea gravel can be difficult to walk on.
• The protective ability of pea gravel is reduced in rainy, humid, and freezing weather conditions.
• Pea gravel can be a falling hazard if displaced from the playground area to a nearby hard surface (sidewalk, decking, or patio, for example).

Play Sand

ADVANTAGES:

• Play sand will not pulverize and decompose.
• Mold and fungus growth is not generally an issue.

DISADVANTAGES:

• Play sand can be difficult to walk on.
• The protective ability of play sand is reduced in rainy and humid weather conditions.
• Animals are attracted to sand unless it can be covered when not in use.
• Play sand sticks easily to shoes, clothing, and skin.
• Play sand can scratch floor surfaces if tracked inside.

Recycled Rubber Mulch

ADVANTAGES:

• Recycled rubber mulch does not generally need to be replaced or renewed each year. Many manufacturers claim that rubber mulch can last approximately 50 years without needing replacement. Check with recycled rubber mulch suppliers for any guarantees or warrantees that may be available.
• Rubber mulch tends to be cleaner and less likely than other loose-fill materials to produce dirty clothing, hands, and shoes during active play.
• Does not cause scrapes, scratches, or splinters from falls.
• Animals and insects are not attracted to rubber mulch.
• Mold and fungus growth is not an issue.

DISADVANTAGES:

• Recycled rubber mulch may need to be raked periodically to maintain appropriate depths in high traffic areas.
• Colors on recycled rubber mulch may fade over time.

Other Protective Playground Surface Options

Rubber Tiles, Rubber Mats, and Poured-in-Place Surfaces

Rubber tiles, rubber mats, and poured-in-place surfaces are initially more expensive surface options than loose-fill materials, but they usually require very little maintenance over time. To determine whether one of these options would be more cost effective than a loose-fill material, consider how many children might potentially use your backyard playground equipment and for how many years. Larger families, for example, may prefer to pay more on the front end for a surface that will be easier and much less expensive to maintain over many years of active use.

ADVANTAGES:

• No means of containment is usually necessary.
• Surfaces are wheelchair accessible and easy to walk on.
• Displacement of materials is not an issue, so the protective ability of these surfaces remains consistent even in high traffic areas.
• Surfaces require very little maintenance over time and are easy to clean.
• Debris such as broken glass and other sharp objects which can cause injury are not easily hidden in these surfaces.
• Animals and insects are not attracted to the surface materials.
• Mold and fungus growth is not an issue.

DISADVANTAGES:

• The area under the surface usually requires special preparation. Contact the manufacturer or supplier for details.
• Surfaces may require professional installation.
• Rubber tiles may curl and cause tripping if not installed correctly.
• Some surfaces may be damaged by frost.

Conclusion

No protective playground surface of any type or depth can prevent all injuries. Nonetheless, installing a protective playground surface as the foundation for your backyard playground equipment is essential for improving playground safety. The most appropriate playground surface for your needs is up to you, but whatever choice you make will be a significant step toward protecting the children who use your playground equipment from serious injuries due to falls to the surface.

Sources:

CPSC Document #323. “Home Playground Safety Tips.”
CPSC Document #324 “Outdoor Home Playground Safety Handbook.” 2005.
CPSC Document #1005. “Playground Surfacing Materials.”
CPSC Report. “Home Playground Equipment-Related Deaths and Injuries.” July 2001.
CPSC Report. “Special Study: Injuries and Deaths Associated with Children’s
Playground Equipment.” April 2001.

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