15.04.2011 - Ausgabe: 2/2011

Synthetic turf – the everyday surface for training and league matches

By Michael Pülm (Dipl.-Ing.), Ingenieurbüro Richter GmbH

Technology and costs
Something that is unfortunately seen all too often on pitches: "Pitch closed". During unfavourable weather conditions, pitches can be used to a limited extent only – a pitch with an all-weather surface could at least help for regular training.

The state-of-the-art all-weather surface is a synthetic turf: it can also be played on and withstand all strains in rain and persistent humidity. For the football clubs, the question of the need for a synthetic turf does not arise, but the tiresome question about the costs and financing of this all-weather surface do. So what costs can be expected and to what extent can a club reduce the costs by providing its own services?
Now, the question about the costs is quickly asked, but not quite as quickly answered – akin to the question: "What does a blue car actually cost?"
A synthetic turf is not a special carpet, but a system consisting of several layers with special requirements and properties.
Here, the subsurface can be assessed with criteria of classic civil engineering – but with increased demands on the evenness and permanent water permeability.
The elastic layer must be regarded as a connection element between the supporting subconstruction and the actual surface made from synthetic turf. This layer made from rubber granulate and binding agents must guarantee a high level of impact resistance over a long period of time to protect joints and ligaments and to reduce injuries.
The "green carpet" made from synthetic fibres – the actual playing surface – is now placed on top. The fibres of this carpet determine crucially the football properties (rolling properties of the ball, ball reflection, etc.) of the sports surface. Even when used excessively every day, the fibres should – similar to the stalks of natural grass – stand up again as required. This requires supporting the fibres by their subconstruction (cross-section shape and material thickness), the density and arrangement of the fibres and by filling up the cavities between the individual fibres/fibre clusters.
As a rule, non-filled and filled systems are distinguished. The support of the fibres in a non-filled system is carried out via a narrow arrangement of fibres of different lengths, which means that a tight-knit, fluffy "carpet" is created. With non-filled systems, a lower layer made from quartz sand and a filling of rubber granulate on top are used.
Non-filled synthetic turf has been used increasingly over the past few years in Switzerland, in particular, but is not yet established in our country due to high investment costs. When comparing the two systems of filled/non-filled, however, not only the investment costs, but the later maintenance and repair costs must be taken into account in advance – providing that the most economical and not the currently "cheapest" system is to searched for.
Now, so far the following may have already become clear: synthetic turf is a system consisting of several cost-influencing factors that must be considered in a differentiated way. For this reason, it makes sense to first clarify the following questions when choosing a synthetic turf: Who uses the synthetic turf? Usage period per week? Type of usage? What are the circumstances of the position and environment? How should the edge areas of the pitch be fastened? What pitch dimensions are required?

The clarification of the above parameters can be carried out by the club/council without a major effort. To clarifiy and determine the main technical parameters, DIN 18035-7 and DIN EN 15330 should be applied in order to specify comparable parameters for a tender. But even then, some questions remain open in respect of the "carpet", because both the fibres and the filling material are offered by the manufacturers in a broad range. The following must be distinguished here: Carpet back (Supporting material (carpet back) and latex quality for gluing the fibres to the back).
Fibres (Type, base material, thickness, cross-section shape, Number of stitches, How many fibres per stitch, Length of the fibres, Length of the fibre over the filling, Surface weight (kg/m²)). Scattered granules (New or recycled material / Natural rubber products (rubber – SBR, EPDM, TPE, TPU, etc.) / Organic products / Grain size and shape / Bulk density / Filling height)

All above parameters have a direct impact on the quality, the longevity and ultimately on the costs. An intensive comparison and a requirement-compliant weighing up are mandatory here.
Back to the initial question: What does a synthetic turf actually cost? The answer is provided on the basis of a practical example.
Conversion of a hard floor to a synthetic turf with the following boundary conditions:
• Hard floor with concrete surface in accordance with DIN 18035-5
• The concrete surface is removed; the supporting layer below can still be used
• Upgrade of drainage and connection to the existing drains
• Profiling of the pitch surface (roof profile approx. 0.8%)
• Creation of a boundary lining (gutter stone) as circumferential delimitation for the synthetic turf
• Elastic layer d = 25 mm
• Synthetic turf surface type B in accordance with DIN 18035-7
- partly filled (rubber/sand)
- mono filament, straight fibre
- granules = TPE (no SBR)
• Training lighting exists – no need for action
• Pitch size 105 x 68 m = 7,140 m² + safety area = 7,630 m²
 

The costs stated in the Table are average prices from tenders in 2010. As regards construction costs, the high relevance of the elastic layer and the actual covering surface becomes clear. In total, these two functional elements make up about 84% of the total construction costs. It therefore makes sense to have a close look at these two elements and to consider various alternatives and variants – after all, the new synthetic turf should not only fulfil the requirements set out by the user, the economic framework conditions should also be observed.
And this takes us to the next question: can the tried-and-tested helpers of the club not put their joint efforts to performing part of the work themselves and thereby reducing the construction costs? As a rule, nobody should be stopped in their drive, as long as a clear delimitation is specified between the work of the commissioned construction company and that of the free helpers. The work of the construction company is carried out under a construction contract, which includes a time-limited fault liability. For this reason, it is important that the club does not perform any of the services stated in the construction contract – work on the actual pitch is therefore out of the question. Outside the synthetic turf, the option arises to pave paths, anchor barriers or fasten and design other boundary areas. Taking into account the materials required, own services can certainly save several thousand euros - but savings in excess of some EUR 10,000 seem unrealistic.
Summary

A synthetic turf offers very big benefits for the training and league matches of a football club. But before the new all-weather surface can be inaugurated, many factors and marginal conditions must be discussed, compared and noted. This allows reducing costs and still creating improved training and competition conditions.
The costs for a synthetic turf are comparable to those of a high-quality carpet surface for a living room. With a pitch size of nearly 8,000 m², however, this results in very high investment costs, which can be reduced by own services