Ask an installer what sits under a playground lawn and the answers split quickly. Some owners treat the layer beneath the turf as a comfort accessory they can skip.
Others assume a thicker grass roll does the same work as a shock pad under artificial grass. Both assumptions fail at the same moment, when a child falls from the top of a frame. We have quoted enough of these builds to watch both assumptions fail at handover. We walk the mechanism first, then map where a pad is essential and where it is optional.
What Impact Attenuation Actually Means
Playground standards reduce the whole question to one property. Impact attenuation is what protective surfacing exists to deliver – shock-absorbing material in the use zone around equipment, per the CPSC Public Playground Safety Handbook. Falls are among the most common playground hazard patterns, which is why the handbook calls surfacing under and around all equipment crucial protection.
Why the Definition Matters
The handbook states the outcome plainly. A fall onto a shock-absorbing surface is less likely to cause a severe head injury than a fall onto a hard surface. Per the NPPAS surfacing brochure, more than 200,000 children need emergency room care for playground injuries each year. Those two lines explain why installers argue about this layer before anything else.
How a Fall Gets Managed
During an impact, the surface has a brief window to slow the head. G-max measures the maximum acceleration an impact produces, while the HIC score tracks how the acceleration builds and fades, per the ASTM F1292 official page. A pad does not make the ground soft. It lengthens the stopping distance, so the same energy reaches the body more gently.
Critical Fall Height: The Number That Drives the Match
Every pad is specified against a single number. Critical fall height is the approximate fall height below which a life-threatening head injury would not be expected. Matching then works in one direction – the surface rating must meet or exceed the tallest equipment on site. That logic is how surfacing fits into the wider playground safety picture, and it is why a shock pad under artificial grass is chosen before the turf itself.
The rating comes from laboratory testing of the turf-pad combination rather than the pad alone. ASTM F1292 describes a critical fall height test plus a separate installed surface performance test. The gap matters because compaction, weathering and wear can erode field performance over the years. The turf half of that pair is its own specification – the playground artificial grass page collects the roll-side options.
Note: pad thickness is matched to the equipment’s critical fall height, so taller structures need thicker pads. No thickness chart replaces the tested rating of the finished system.
What Happens Without a Pad, and What Grass Alone Covers
A lawn without a shock pad under artificial grass still looks finished on day one. The difference hides in the fall data, not the appearance. Child-safety bodies are blunt about natural grass. Safe Kids Worldwide lists grass, dirt and gravel among surfaces to avoid under play equipment. Per HealthyChildren.org, the pediatricians’ parenting site, grass may seem