By: Dennis Frank (ISP GmbH - Institut für Sportstättenprüfung) – Institute Director and registered playground inspector per DIN SPEC 79161
One of the most important factors when constructing a new playground is to ensure that the correct surfacing is used. The first thing is to make sure that the fall protection surfacing does what it is meant to do and thus conforms to the requirements of the German version of standard EN 1176 part 1. This section defines the general safety and testing specifications as set out in the European standard that applies to play equipment and playground surfacing.
The standard stipulates that impact-absorbing surfacing must be provided across the whole potential impact area under all equipment with a free fall height greater than 60 cm and also under all equipment that can involve forced motion (such as swings, slides and carousels).
In addition to the standard loose filling materials (sand, gravel, mulch), other materials such as coloured wood chips, matting and seamless plastic surfacing are routinely used as fall protection surfacing. New impact-absorbing surfacing systems are continuously being developed. Surfacing made of infilled and non-infilled artificial turf and combined EPDM mulch products are increasingly becoming available and are also appearing on the German market.
There is a wide range of materials that can be used to construct fall protection surfacings. These materials can be classified in the following groups:
Group 1: Grass and topsoil
Group 2: Natural loose filling materials
Group 3: Other materials
When selecting the material, not only the purchase and maintenance costs need to be taken into account; the durability, sustainability and the potential effects that the environment can have on the material must also be considered. In the following, the characteristics of the various groups are reviewed in more detail.
Grass and topsoil: The maximum fall heights under which grass and topsoil may be used as surfacing are stipulated in table F.1 of German standard EN 1176-2008-08 ("Surfacing relative to permitted free fall heights"). In Germany, topsoil may be employed under equipment with a maximum fall height of ≤ 1.0 m while grass can be used under equipment with a maximum fall height of ≤ 1.5 m. The specification in the case of grass applies solely to Germany; in other European countries in which the standard is used the allowable maximum fall height for which grass may be employed as surfacing is only ≤ 1.0 m.
In general, the use of grass as fall protection surfacing in areas in which there is a maximum fall height of 1.1 - 1.5 m can be problematic as it is difficult to maintain the integrity and thus the impact-absorbing effect of sward where children's feet will be constantly scuffing it during play. The result of this effect can frequently be observed in the areas of swings, slides and carousels.
Although the initial acquirement costs of grass and topsoil are low, it must be borne in mind that this type of surfacing will require time-consuming upkeep by personnel, meaning that use of this surfacing will be associated with high outgoings for maintenance.
Natural loose filling materials: The second group in our review is that which is most commonly used in public German playgrounds. The group of natural loose filling materials includes minerals such as sand and gravel and the organic fall protection materials bark mulch and wood chips. As table F.1 of German standard EN 1176 shows, the stipulated grain size and minimum thickness of the layer determine with which maximum fall heights these materials may be used. For example, it can be concluded from the information provided in the table that the following minimum layer thicknesses of materials must be provided for the following maximum fall heights: sand with grain sizes 0.2 mm - 2.0 mm (without sediment or clay inclusions); wood chips with grain sizes 5 mm - 30 mm (mechanically shredded, no work processing materials, no bark or leaf inclusions); according to the standard, a minimum layer thickness of 200 mm of these loose materials must be provided for a maximum fall height of ≤ 2.0 m and a minimum layer thickness of 300 mm for a maximum fall height of ≤ 3.0 m. However, when calculating the minimum layer thickness, an additional minimum of 100 mm must be added to compensate for the abrasion effect during play (DIN EN 1176:2008 4.2.8.5.1). This means that where the maximum fall height is 2.0 m, a minimum layer thickness of 300 mm of these loose filling materials must be provided.
If the loose material exhibits variations with regard to grain size, grain size distribution or composition, the above table cannot be used to determine the relevant requirements with regard to maximum fall height. In this case, the material must be assessed and evaluated by an institute that has been accredited in accordance with the requirements of German standard EN 1177:2008.
While loose filling materials have the advantage of being relatively inexpensive to acquire, surfacings made of these materials are not cheap to maintain. For example, a sand-based fall protection surface will need to be turned over and sieved annually to free it from undesirable contaminants. Bark mulch rapidly decays, meaning that it needs to be regularly replaced in order to retain the required minimum layer thickness.
Perhaps the main disadvantage of loose filling materials is that they need to be cleaned daily to remove extraneous matter such as excrement, glass shards, cigarette ends and syringes, the presence of which is difficult to detect and thus requires considerable effort. Surfacings in which soiling becomes extreme will need to be replaced completely, something that might even require temporary closure of the playground.
Other materials: The third group represents a vast variety of materials ‒ "Other materials and layer thicknesses". These include loose filling materials with grain sizes that do not meet the requirements stipulated for natural filling materials and the extensive group of synthetic fall protection surfacings, such as plastic surfacings and tiles that are installed in-situ. These two subgroups constitute the major proportion of all synthetic fall protection systems that are employed.
The permitted maximum fall heights are determined by the material structure and thickness. In-situ installed systems generally consist of an impact-absorbing base layer made from PUR-bound SBR-rubber granulate with a more firm upper layer made from PUR-bound EPM granulate. Fall protection tiles, on the other hand, consist of one or two layers of various materials, such as SBR or EPDM granulate, and are available in a range of colour finishes and forms. The thickness of these systems determines the maximum fall heights for which they may be used. They also provide the widest range of options when it comes to playground design.
German standard EN 1176 does not provide standardised stipulations for the corresponding fall heights in connection with these systems. Here the shock-absorbing properties must be determined in terms of the HIC value per German standard EN 1177:2008 by a testing institute accredited in accordance with German standard EN ISO/IEC 17025. The critical fall heights and the corresponding required thicknesses for each system must be individually determined and documented in a test report per German standard EN 1177:2008.
Synthetic fall protection systems are comparatively expensive to acquire; the actual cost will be determined by the materials used and the maximum fall heights for which they are to be installed. At the same time, the maintenance costs are relatively low in comparison with those associated with the two previous groups. Most synthetic systems have a smooth surface finish so that soiling in the form of loose leaves or rubbish can be rapidly removed.
Main factor
The fall protection surfacing systems of the groups described above differ with respect to cost, necessary minimum thickness and the cleaning and maintenance required. However, the most important factor associated with these surfaces is their ability to provide good shock absorption; in other words, if used as surfacing in a playground, they must be able to adequately cushion the impact of a child falling from equipment and thus prevent that child from incurring critical, life-threatening injuries. The impact-absorbing capacities of materials can be determined in the form of their HIC value as specified by German standard EN 1177:2008.
Suitability
When selecting a fall protection surfacing, the factors of safety-relevant shock absorption properties, acquirement and maintenance costs need to be considered, but it is also important to take into account suitability. Not all the materials described are suitable for use in all situations. Sand is not an appropriate material to use in a retail centre while synthetic fall protection tiles would be out of place in a playground located in a natural forest area. Other factors that are relevant are the possible indirect maintenance and consequential expenses. For example, sand used as a fall protection surfacing can be transported as soiling into schools and classrooms or can act as an abrasive and increase the wear and tear to the equipment. Such potential consequential costs need also to be evaluated when deciding which fall protection system to use in a particular context.
Conclusions
In most cases, the fall protection system that can be considered to be 'appropriate' in any given situation will represent a compromise. It is primarily essential to ensure that the system retains its protective properties and that the risk of the impairment of these by external factors is reduced to a minimum. But an optically attractive combination of equipment and fall protection surfacing is necessary if children are to be encouraged to use a playground.
Image: ISP GmbH - Institut für Sportstättenprüfung
Children and youngsters rushing here and there, screams of pleasure, high spirits and laughter ‒ as soon as a trampoline park opens its gates, it takes no time at all until the visitors arrive.
Fall protection surfaces vary in terms of cost, minimum installation thickness and cleaning and care requirements. It should be noted that the most important property of these surfaces is the safety-related shock absorption. This is the surface's ability to reduce the impact energy that occurs when a child falls from a piece of play equipment. It prevents a critical, even life-threatening, injury.
