What lies beneath: learn the pros and cons of a variety of surfacing solutions.

One of the most important aspects of providing a safe play environment is the installation of high-quality surfacing with proper impact attenuation properties. When installed correctly, safety surfacing greatly reduces serious injuries that can occur if children fall from the play structure.

We've come a long way since the mid-'70s, when it was not uncommon to find playgrounds with concrete or asphalt surfaces (with asphalt being the preference as it was "softer" than concrete). Unfortunately, serious injury was a regular occurrence, and both material providers and facility owners sought to provide a surface that was softer to help attenuate falls and reduce injury. At that time, sand and pea gravel were both readily available and inexpensive, and were generally accepted as a better alternative than the hard surfaces of the past.

However, sand became hard when wet, and was often polluted by animal waste. Both surfaces were easily thrown by children and were difficult to walk or run in. Then, with the advent of the Americans with Disabilities Act (ADA), the surfacing industry evolved again, as the product now needed to provide a firm, stable and slip-resistant footing for mobility devices to wheel across, which was not possible with either sand or gravel.

There are several industry-accepted playground surfaces available that provide the cushioning properties needed, as well as the firm stability required for the ADA. Because the industry is constantly experimenting, and new surface products are introduced on a regular basis, park and recreation managers should know the benefits and drawbacks of the most commonly accepted types of surfacing, in order to make the choice that best suits any play area.

It also helps to be familiar with two sets of federal guidelines: the U.S. Consumer Product Safety Commission's (CPSC) Handbook for Public Playground Safety (CPSC Pub. 325) and the U.S. Access Board's ADA Accessibility Guidelines for Play Areas, covering compliance under the ADA. According to these publications, playground surfacing must allow children to approach and enter the playground safely, as well as minimize the risk from falls.

When planning a play area, your playground manufacturer will calculate its "use zone." This zone includes all surfaces under the equipment, as well as the distance outside and around the equipment that a child may fall in the normal course of play. The use zone is the minimum area that surfacing should be placed in, though some play environments extend the use zone to increase the play area or enhance the surrounding environment. The depth of surfacing required depends on the height of the play equipment, and the type of surfacing used.

A critical fall height (CFH) is assigned to the components within the play area, and is defined as the "fall height below which a life-threatening head injury would not be expected to occur." The CPSC Handbook indicates recommended depths of materials calibrated to various fall heights. For example, nine inches of compressed wood chips will protect children falling from a height of 10 feet, while the same depth of coarse sand only protects from a fall height of four feet, less than half the distance. Although it may cost more, six inches of shredded rubber protects children from fall heights of 10 to 12 feet.

So what are the choices and benefits of each type? Surfacing can be divided into two groups: loose fill--such as wood fiber and rubber chunks; and unitary, or solid surfaces, such as bonded or poured rubber. Generally speaking, loose fill surfaces are less expensive, but may require more maintenance during the life of the product. They require adequate drainage, as well as containment borders to prevent migration outside the play area.

They should also be installed over an underlayment of geotextile fabric, to prevent mixing with the under surface and "grow through" of plant material. Choosing wear mats to lay on the surface in areas like the base of swings and slides, can help prevent displacement. Loose fill surfaces are also harder to keep clean, as trash can be mixed in and not easily noticed. Some may not provide adequate accessibility.

Solid or unitary surfaces provide excellent ADA accessibility. Unitary surfaces will not require topping off, and are easy to clean, saving maintenance costs throughout the life of the product. They do, however, require a higher initial investment than with loose fill surfaces. They must be installed over a prepared hard surface, like concrete or asphalt (or in some cases, crushed stone) and proper drainage is important. They must not be installed over grass or gravel. Unitary surfaces, because they are more unyielding than loose fill materials, may also result in more finger breaks after a fall to the surface.

So how do you choose what's right for your area? Jim Pryor, director of parks and recreation for Kernersville, N.C., says that they considered the initial investments, then chose bonded rubber surface product for their playground. Pryor adds, "We have used most all types of surfacing, and felt that the low maintenance associated with this product was well worth the initial investment.

We also let our community take an active role in the choices of equipment and surfacing, so we brought samples of the surfacing available to all our meetings, and bonded rubber won with 87 percent of the vote."

To help you make a surfacing decision, the following are the most widely accepted types of surfacing, and a basic summary of each.

Engineered Wood Fiber

Not to be confused with wood chips, bark mulch or sawdust, engineered wood fiber is specifically ground to meet the needs of the playground industry. Generally one to three inches in length, the individual pieces of fiber knit together to provide acceptable access to mobility devices, in accordance with ASTM F1951. Sawdust and similar materials will not knit, causing the wheels of mobility devices to dig in and stick. Engineered wood fiber is one of the most common surfaces found on the modern playground.

Engineered wood fiber is one of the lowest initial investments, but will require additional investment over the life of the product. Regular maintenance is required to maintain consistent depths and attenuation properties because the product will both migrate and pack down as children run, scuff and play on it. In areas where heavy winds are common, it may even blow away. Engineered wood fiber is a natural material, and as such, is subject to the environment. It will decompose through time, requiring occasional "topping off" to maintain its intended depth. Also because it is a natural material, wood fiber can be subject to mold and fungal growths.

It is readily available and can be easily installed by a volunteer crew, which can save money when compared to hiring professional installers. It provides good drainage properties, as long as the grade and initial preparation of the site has been adequately addressed. "Drainage is the key to a successful wood fiber installation," says Jeff Robinson, the brand manager of Specialized Maintenance and Park Services for Mecldenburg County, N.C. "The better the drainage, the longer your fiber will last. Without adequate drainage, wood fiber will decompose at a faster rate, and can also float away."

Wayne Darcy from the Atlanta Parks Department agrees. He says, "As long as it doesn't wash away or get kicked away, wood fiber works well, as long as you keep it replenished and clean." Wood fiber also provides a natural, appearance to the play area. In cases where the budget is limited, choosing engineered wood fiber may allow you to invest a larger majority of your initial funds into equipment, rather than surfacing.

Poured Rubber

Also known as "Poured-in Place," this surface consists of two layers, a cushioning layer and a colored wear layer. Tiny rubber granules are mixed with a binder and poured into place at the site. This rubber surface offers a colorful, low-maintenance surface option, but will also incur one of the highest initial investments, and can surpass the cost of the equipment as a percentage of total budget. It must also be installed by a trained professional crew. However, during the life of your playground, it will require little maintenance, is not displaced during play, and is easy to clean, as trash can not mix into the product.

Poured rubber provides one of the best ADA-accessible surfaces too, providing an easy way for wheelchairs to roll over the surface. It also offers the most design options; colors can be mixed to produce varying hues, or laid side by side to create artistic patterns and graphic designs. Additional games, such as hopscotch and four square can be incorporated, adding additional play value. It will not decompose, but may be subject to vandalism.

It is also important to note the choices of binder; standard aromatic binders will "yellow" the overall appearance of the color, which is especially noticeable on lighter hues. To avoid this, be sure to specify an aliphatic binder. There is also a rubber curb that is available for containment purposes. Darcy says, "We have found that rubber curbing works well as a border. We've installed it around entire playgrounds, and have also used it in combination with small areas of rubber surfacing to stabilize problem areas, such as short slopes that connect play areas, even though we may use wood fiber as the main play area surface."

Bonded Rubber

A unitary surface that is rapidly growing in popularity, bonded rubber surfaces use recycled tires that are cleaned, then dyed in a variety of colors. Where poured rubber is a granular product, bonded rubber resembles a shred-in texture, but is similarly mixed with a binder on site before being installed. Also like poured rubber, this product must be installed by a trained crew, but in some areas, may provide a lower cost alternative to customers desiring a unitary surface, depending on the distance the product must be shipped. Repairs to the surface are less expensive than poured repairs.

After selecting this type of surfacing, Pryor thinks his town made a great choice. "Last time I was at the playground with my family, I saw a young girl fall from a climber onto her back and head. She popped right up, and went back to playing without shedding a tear. That made me feel very good about our choice."

Bonded rubber can be installed in a single color, or mixed together to create a subtle blended shade. It does not have the same graphic options as Poured-in Place, because the shred texture does not lend itself to precision graphic design. Bonded rubber is made of recycled tires, so it can also be considered environmentally friendly.

Loose Fill Rubber

Loose fill rubber is a surface that is also made of ground tires. (Be sure to choose certified material created specifically for the playground industry, to prevent the presence of steel belt particles.) Loose fill rubber provides one of the most superior fall attenuation ratings of all surfaces; installed at a 6-inch depth, it can attenuate a fall height of 10 feet. It is easy to install, and can often be done by a volunteer crew, saving money over professional installation. As it is heavier than other loose fill options, it is less likely to blow away in windy conditions. Loose fill rubber does not compact over time, and will not decompose, which reduces the need for top offs. As it is non-organic, it is not ideal for microbial growth. It is available in a variety of colors, making it unique among loose fill options.

Robinson says that although they have used primarily wood fiber during the past several years, they are making a move toward loose fill rubber as their primary surface choice. "With 90 playgrounds in our system, we were looking at a budget figure of $100,000 for replenishment and maintenance of our wood fiber. We tried loose fill rubber in several playgrounds, and found that it does not decompose or require the regular maintenance of wood fiber, and will save us a great deal of money over the life of the playground." Robinson also says to consider the life of the playground, and not just the initial investment--loose fill rubber could be more economical than wood fiber.

Rubber Tile

Playground surface tiles are considered unitary; once they are installed, they provide a single smooth surface. They are environmentally friendly, and are made of recycled rubber.

Tiles are often used for indoor playground environments, as they offer the benefit of a unitary surface, but do not need to be mixed or poured on site.

Tiles can be installed in a single color, or varied to produce checkerboard, hopscotch or other interesting patterns. The method of installation generally requires a professional crew, but skilled volunteer installation may be possible. There is some variation between manufacturers on installation, some tiles lock together; others are simply glued to the undersurface. Like most unitary surfaces, tiles must be installed over a hard surface like concrete or asphalt.

When making your final choice, it is important to consider the needs of your play area. Initial budget investment, accessibility, maintenance throughout the life of the playground and overall appearance are all important considerations. Your playground company is a great source of information on the cost of each type as it relates to your unique project.

For more information, check out the following Web sites:

* Guide to the ADA Accessibility Guidelines for Play Areas: www.access-board.gov/play/guide/intro.htm

* ASTM Guidelines: www.astm.org

* CPSC Handbook for Public Playground Safety: www.cpsc.gov/CPSCPUB/ PUBS/325.pdf

* National Playground Safety Institute: www.nrpa.org/nspi

RELATED ARTICLE: A quick look at surfacing solutions.

Wood Fiber

Advantages

* low initial cost

* ease of installation

* good drainage

* less abrasive 

* less attractive to animals vs. sand

* attractive appearance

* readily available

* less finger breaks vs. unitary rubber

Disadvantages

* holds moisture

* can combine with dirt (becomes dirty)

* decomposes over time

* depth reduced from use (kick-out)

* can be thrown at children's eyes

* subject to mold, mushroom growth

* hides trash, excrement, broken glass, etc.

* spreads easily outside contained area

* subject to theft by neighbors for plants

Poured Rubber

Advantages

* low maintenance

* easy to clean

* consistent shock absorbency 

* material not displaced during play

* good footing

* best ADA surfacing

Disadvantages

* initial cost very high

* must consider drainage

* subject to vandalism (high cost to replace)

* rubber may peel

* more finger, arm and lower leg breaks

Bonded Rubber

Advantages

* low maintenance

* easy to clean

* consistent shock absorbency

* material not displaced during play

* good footing

* good for ADA surfacing

* repair much less expensive vs. Poured

Disadvantages

* initial cost high

* must consider drainage

* subject to vandalism

* children will pick or pull up pieces

* more finger, arm and lower leg breaks

Shredded Rubber

Advantages

* ease of installation

* has superior shock-absorbing capability

* not ideal for microbial growth

* less abrasive

* less attractive to animals

* does not deteriorate over time

* long shipping lead time

* less finger breaks vs. unitary rubber

Disadvantages

* can be flammable 

* may soil clothes

* may melt in home dryers

* depth reduced from use (kick-out)

* can be thrown at children's eyes

* may be swallowed

* hides trash, excrement, broken glass

* spreads easily outside contained area

* subject to theft by neighbors for plants

Rubber Tiles

Advantages

* low maintenance

* easy to clean

* consistent shock absorbency

* material not displaced during play

* easy to replace a damaged tile

* good for ADA surfacing

* can be installed indoors

Disadvantages

* initial cost higher

* must consider drainage

* subject to vandalism

* more finger, arm and lower leg breaks