PLAYGROUND
Playground mulch depth: what the CPSC handbook requires
Playground surfacing is the one place where mulch depth is a safety specification rather than a gardening preference. The U.S. Consumer Product Safety Commission sets it in the Public Playground Safety Handbook (Publication 325), and the rule is not a range you get to choose from.
The rule, quoted
From the handbook's loose-fill notes:
"Never use less than 9 inches of loose-fill material except for shredded/recycled rubber (6 inches recommended). Shallower depths are too easily displaced and compacted."
So there are two numbers, and which one applies depends on the material:
- Shredded or recycled rubber: 6 inches recommended as the floor.
- Everything else loose-fill — sand, pea gravel, wood mulch, wood chips: never less than 9 inches.
Depth is set by fall height, not by the equipment size
The handbook's Table 2 gives the minimum compressed depth of each loose-fill material against the fall height it protects to. One row that matters for rubber buyers: the handbook lists 9 inches of shredded or recycled rubber as protecting to a fall height of 10 feet. The compressed depth is the number that counts — the handbook is explicit that the depths shown assume the material has been compressed by use and weathering and is maintained at the stated level.
That word "compressed" is the part people miss. You do not order 6 inches of rubber and expect 6 inches to still be there in August. Loose-fill settles, and the handbook says directly that loose-fill surfacing requires frequent maintenance to ensure surfacing levels never drop below the minimum depth.
Where the material disappears fastest
The handbook names the spots: areas under swings and at slide exits are more susceptible to displacement, and it suggests impact attenuating mats in those places to reduce it. It also suggests marking equipment supports with a minimum fill level, so the original depth can be seen and restored rather than guessed at.
Two more requirements sit alongside depth: the perimeter of the playground should contain the loose-fill material, and good drainage is essential — standing water reduces the surfacing's effectiveness and leads to compaction and decomposition.
The material warning mulch buyers need
The handbook carries a specific warning about wood mulch: mulch containing chromated copper arsenate (CCA) treated wood should not be used, and mulch where the CCA content is unknown should be avoided. That rules out some recycled-wood products for playground use regardless of how much you order.
Ordering to a depth, not to a bag count
Once you have the depth and the area, the volume is arithmetic: cubic feet = square feet × depth in inches ÷ 12, and cubic yards = square feet × depth in inches ÷ 324. For the 6-inch rubber minimum over a 484 sq ft area that is 484 × 6 ÷ 12 = 242 cubic feet, or 8.96 cubic yards.
Bag counts need the bag volume as well, because playground rubber is sold in smaller bags than garden mulch — commonly 0.8, 1.25, 1.5 and 2 cubic feet. The playground mulch calculator does that arithmetic with the bag size included, and the rubber mulch calculator covers the garden case where you are not working to a fall-height requirement.
What this page does not tell you
It does not choose the depth for you. Fall height comes from your equipment and its installation height, and the handbook's Table 2 is the source to read the material-by-material figures from directly. This page quotes the handbook's stated minimums and maintenance rules; it is not a substitute for reading it, and it is not a safety certification of any product you buy.
Source
- U.S. Consumer Product Safety Commission, Public Playground Safety Handbook, Publication 325 — loose-fill surfacing notes and Table 2. Quote and rules above checked against the publication text.
Related reading: How deep should mulch be — the garden depth question, which has a different answer and different sources.