Impact area and critical fall height (EN1177)

How to calculate the area on a playground which should be covered with safety flooring because a child might fall on it (impact area)?
How to define a critical fall height according to EN1177 standard on various types of playground surfacing (rubber flooring and loose fill materials)?
In this entry you will find the answer to these crucial questions, particularly for those who plan a playground or a play area, no matter if it’s for private or public use.

Let’s start with the rules regarding critical fall height.
Safety flooring is required for equipment with a critical fall height higher than 0.6 m, according to the European Standard EN 1177 (in the UK known as BS EN 1177). However, even for these areas under 0.6 m, some protective surfacing should be laid. On the other hand, the maximal fall height on a playground is 3 m, meaning that free height of a fall from any place on a playground should not exceed 3 m.

Rubber granulate surfacing


Fall height on a playground covered with safety tiles

Image courtesy of photostock /

Rubber granulate tiles or wet-pour surfaces have to be individually tested (HIC tests) to obtain critical fall height values. The manufacturer is obliged to inform what critical fall height specific products have and, if requested, present a corresponding certificate.

Loose fill materials

For loose-fill materials the critical fall height has been determined by EN 1177 standard. One has to bear in mind that loose-fill materials have to be suitable for use on children’s play areas. Another factor which has to be taken into account is the material loss, caused by the wind and playground users. Because of that, loose materials have to be periodically replenished. Another condition is that the minimal depth of the loose fill material is 30 cm.

Material Comments Layer depth Max. fall height
grass the use of the grass surface should be monitored and maintained; areas of wear should be strengthened; a depth test of 150 mm must indicate few stones / hard objects left to each country 100 cm
wood chips 5 – 30 mm particles (no bark or leaves; no wood-based materials) 30 cm 200 cm
40 cm 300 cm
bark 20 – 80 mm particles (chopped bark from conifers) 30 cm 200 cm
40 cm 300 cm
sand 0.2 – 2 mm particles (washed; without silt or clay) 30 cm 200 cm
40 cm 300 cm
gravel 2 – 8 mm particles (round and washed; without silt or clay) 30 cm 200 cm
40 cm 300 cm

Another common-sense safety requirement as to the surfacing which EN 1177 also emphasizes is that playground surfacing should have no entrapments, sharp edges or projections.

Calculating impact area

Impact area is the area which can be hit by the falling user, in other words minimum space around equipment on a play area. This area should be free of obstacles in the falling space as well as covered with impact-absorbent safety surfacing, sufficient for the given critical fall height.

How to calculate how big this area should be? Use these simple rules to design a safe play area, no matter if it is going to be in your backyard or on a schoolyard.

  • areas under 0.6 m critical fall height → no legal requirement, but 1 m from the equipment is a common-sense practice,
  • areas up to 1.5 m critical fall height → 1.5 m from the equipment should be covered with safety flooring,
  • areas over 1.5 m critical fall height → use this formula: 2/3 fall height + 50 cm

For example, a climbing equipment with a critical fall height of 2.2 m should be secured with fall-attenuating surfacing, not only underneath but also in the area of 1.95 m from the edge of the equipment (2/3*2.2m + 0.5m = 1.95 m).

For rocking euipment or swings, please see the European Standard EN 1177, as these requirements are clearly defined. Moreover, manufacturers of playground equipment often provide the details about the critical fall height and impact area, so ask your manufacturer in case of any doubts.

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