A playground should always have some type of protective surfacing under and around the play equipment. There are many types of protective surfacing options to choose from. Wood mulch is one type of loose-fill surfacing material that is appropriate for use on playgrounds. The U.S. Consumer Product Safety Commission (CPSC) has published recommendation guidelines to ensure optimal playground safety.
Mulch should be placed under and around all play equipment where a child’s feet leave the ground. This includes climbing walls, slides, swings, monkey bars, etc. Play equipment that involves the child standing or sitting at ground level does not need protective surfacing. These include such play structures as sand boxes, play houses or activity walls. Loose-fill materials of any kind are not recommended for playgrounds intended for use by toddlers.
The most critical function of protective surfaces is to prevent head injuries as a result of falls from heights. The ASTM F1292 Standard Specification for Impact Attenuation of Surface Systems Under and Around Playground Equipment provides a rating service for different types of surface materials. These ratings are based upon an approximation of the maximum fall-height that would not cause a life-threatening head injury. Each wood mulch manufacturer should provide data on the ASTM F1292 rating for their product.
The potential fall-height (in feet) from the highest play surface is necessary to determine the depth (in inches) of mulch required. Nine inches of wood mulch will protect a fall from 7 feet.
The CPSC recommends installing layers over the top of hard surfaces. The first layer over the hard surface should be 3 to 6 inches of gravel for drainage purposes. The next layer recommended is a geotextile cloth, followed by the top layer of wood mulch.
All loose-fill materials will compress over time. Wood mulch is especially susceptible to compression due to weathering and decomposition. Mulch will compress a minimum of 25 percent over time, so the initial depth of mulch should include compensation for this eventual reduction. If the playground requires 9 inches of mulch, then 12 inches should be used.
Containment & Displacement
Wood mulch is prone to being tracked out of the playground area and into neighboring areas. The playground should provide a perimeter that allows for containment of the mulch. Areas under swings and slides are the most likely areas to suffer from displacement of mulch. Special maintenance is needed to ensure that these areas maintain adequate mulch depth.
To increase the longevity of mulch, proper drainage is critical. Poor drainage speeds decomposition and increases compaction.
Wood mulch should not be CCA-treated wood. CCA is a combination of copper, chromium and arsenic that is used to preserve wood. It is not recommended for use in areas involving direct contact with children.