By Ing. Robert Terp, head of the specialist field of playing, sport and leisure time equipment, generally sworn legally certified expert for sport facilities, playgrounds and swimming baths, technical inspection agency, TÜV AUSTRIA SERVICES GMBH
It is beyond dispute that along with its aesthetic appearance, grass also has other very positive properties and it is for this reason that it is still so popular with playground operators, especially in rural areas, as a covering surface for playgrounds today.
When considering the economic benefit, this must be separated from other factors such as availability, appearance, influence on children and the surrounding environment, effect on choice of games played, maintenance possibilities and its suitability as an impact-absorbing floor under playground equipment.
To start with a short review of the, already superseded standards, in Austria and Germany, where only the impact-absorbing properties of grass are taken into consideration:
Developments over time
In Austria the preceding standard to the playground equipment standard EN 1176/EN1177 was the ÖNORM S4235, last version dated 1990. The guideline values given at that time for the required surface covering in dependence on fall height, were derived from results of tests carried out according to the testing methods given in this standard (HIC). As guide value for an acceptable fall height onto turf / dense grass, a height of up to 2 metres was given. The German standard DIN 7926, which was also valid at that time, also quoted this height.
Although the publication of EN 1176/1177 in 1997/98 brought no changes to the basic testing methods for fall protection flooring used in Austria, the testing requirements were changed. The often quoted Table 4/EN1176 gives only a fall height of ≤ 1000 mm as critical height above a grass surface. The Euro-standard EN 1177 defines this figures with regard to maintenance requirements, but also states that grass can be used without testing for equipment up to this height.
In contrast to Germany, where national legislation determines the maximum fall height on grass as ≤ 1500 mm, in Austria there are no national laws defining the requirements on impact-absorbing playground floor coverings and their approval with regard to fall heights. The EN 1176/EN1177 was and remains the evaluation benchmark, even for court cases.
Peculiarities of grass as fall protection in Austria!
As reaction to the radical change in critical fall height dictated by the standard, at the end of the last century an agreement of the technical inspection agency TÜV Austria was drawn up. This was undertaken as a cooperation between all those involved from the aspects of safety, manufacturing and operation. This agreement, which also allows for fall heights of up to 1.5 m in some cases (as in Germany), is based on tests as per EN 1177.
Over the years however, the general opinion in Austria has accepted that grass is generally suitable for playground equipment with a fall height of up to 1.5 m.
Contrary to this opinion, the values of Table 4/ EN1176 still apply and can only be deviated from in justified cases. It is also stated in this article of the standard that for fall heights above 1 metre, the impact-absorbing properties of grass are dependent on the local climate, which naturally varies greatly throughout Europe. The agreement drawn up in Austria has already taken this factor into consideration and even recorded consequences to be expected for deviation.
Conclusive and decisive however, is always the actual fall protection properties at each site according to application of testing methods as per EN 1177. Why should other rules apply for grass than for other fall-protection materials?
The local conditions (substrate, climate, maintenance) are decisive for the actually existing critical fall height, which must be higher (or at least the same) as the maximum fall height of the playground equipment.
Continuous practical tests on-site, also taking international trends regarding fall-protection mechanisms into account, have provided interesting findings. On the one hand, critical fall heights of more than 2 metres as per EN 1177, have been determined, on the other hand, optically intact turf surfaces have even proven unsuitable for fall heights of up to 1 metre. In some cases, for example, the substrate was unsuitable to support the impact-absorbing action of the grass which grows perfectly well even on brick chippings!
Grass: When and when not!
The suitability of turf as fall-protection floor should be evaluated locally and separately for each playground on the basis of a risk evaluation carried out by an expert. The maximum fall height from playground equipment should not be more than 1.5 metres. As a basis, especially the following points should be taken into consideration during the evaluation, as this also applies for turf surfaces with fall heights of up to 1 metre:
• Is the expected user-frequency of the playground low or high?
• Are some pieces of playground equipment subject to intensive use?
• Depending on the climate conditions – Austria includes both high-alpine areas and the low-lying Pannonian Basin – must regular drought be expected or is sufficient irrigation ensured?
• Can a sustained, unchanged impact resistance be expected due to the ground structure? Is it possible, for example, that stagnant water can collect?
• Can ground structures, roots, etc. disturb the impact-absorbing capabilities?
• Can sufficient maintenance be expected so that an intact turf structure can be maintained and no bare areas form?
Summary
Grass definitely has good qualities for use as a playing surface. From a point of view of fall protection, even for playground equipment with a fall height below 1 m or up to 1.5 metres, however, marginal conditions must also be taken into consideration. The latest findings regarding injury mechanisms following impact on fall-protection flooring, should be enough to remind users that children should not be exposed to unnecessary playground risks.
Even if evaluation of playground equipment, the conditions under which it is used and the structure of the ground make grass as fall protection seem suitable, care must be already taken during planning, to evaluate whether sufficient maintenance of the turf can be guaranteed to ensure efficient fall protection.
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.
