Conveniently, this invention also relates to methods of resurfacing existing playing field surfaces with artificial turf surfaces and relates particularly but not exclusively to a method of resurfacing conventional "porous" surfaces such as brick dust, en-tout-cas, gravel or clay surfaces; more particularly, conventional porous tennis court surfaces. The invention also relates to playing field surfaces when resurfaced by the methods of the invention.

Artificial turf surfaces are favoured over conventional porous surfaces for reasons of care and maintenance and for reasons that the playing conditions of the artificial turf surfaces resemble those of natural grass surfaces. Currently, sand-filled artificial turf surfaces generally comprise a "carpet-like" covering which is "filled" with sand or similar material and is usually laid over a solid base; for example, concrete or asphalt. The turf material is water permeable to allow excess water to pass through the turf material and drain away. The invention is not however restricted to sand-filled artificial turf surfaces but includes any artificial or synthetic turf surface. If a porous surface is to be replaced by an artificial turf surface it is customary to remove the existing porous surface and to lay a concrete or asphalt or other solid base on which to place the turf material. In some cases it is possible to lay an asphalt or porous asphalt layer over the existing brick dust or en-tout-cas surface to provide a base for the subsequent turf material. In order for water to drain away, it is necessary for the underlying solid base to be sloped in some way. This

necessarily results in a sloped turf surface which is acceptable as playing surfaces for some games such as tennis, soccer, hockey, for example; but not necessarily a completely ideal playing surface. Furthermore, such sloped playing surfaces are not acceptable for the playing of a game such as lawn bowls where a flat level surface is required.

It is known, when preparing artificial turf playing surfaces to provide a permeable aggregate base placed over drainage trenches in a levelled earth area which is overlaid with one or more layers of a porous open graded asphalt mix. Such open graded asphalt mix surfaces permit water to drain through to the aggregate base and thus through to the drainage trenches. This type of playing surface allows for a flat level base to be laid over which the artificial turf material is placed. The method, however, due to the cost of the open graded asphalt mix, is quite expensive.

It is therefore an object of the present invention to provide a turf surface which overcomes or reduces the disadvantages or defects of prior art surfaces.

The present invention may therefore provide a surface comprising an artificial turf substantially flatly laid on a non-porous base wherein drainage means are provided in said non-porous base and/or between said turf and said base and also to a method of construction thereof.

The present invention may also provide a playing surface comprising an artificial turf substantially flatly laid on a non-porous base having drainage means formed therein such that water falling on the surface is directed to waste water drains. Preferably the base is formed of suitably reinforced concrete, asphalt or the like and includes drainage slots cut, as by a concrete saw in the base, to carry water to waste water drains. The waste water drains may be situated either within or beneath the base and thus within the vertical bounds of a playing area within the playing surface, or may be situated at some point outside the vertical bounds of the playing area of the playing

surface. The upper surface of the base may be sloped to facilitate drainage of water via the drainage slots or the upper surface of the base may be level and flat in which case the drainage slots are sloped to permit water to run towards the waste water drains.

In an alternative form of the invention, the upper surface of the base may be sloped and a plurality of moulded plastics material forms be provided to provide a level flat surface, including holes or slots to permit the passage of 0 water, on which the artificial turf is ultimately laid. The holes or slots may be disposed in any pattern or configuration in order to drain water from the turf as may be required.

Prior methods of replacing a porous surface with an 5 artificial turf surface are expensive because all loose material must be removed to ensure adhesion of the asphalt layer. Furthermore, artificial turf surfaces laid over concrete or asphalt surfaces suffer from the disadvantage that the playing surfaces are relatively hard and result in 0 greater fatigue and increase the likelihood of injury when compared to for example porous surfaces.

It is a preferred object of this invention to conveniently provide a method of replacing a porous surface with an artificial turf surface which overcomes or reduces ~ the disadvantages of known methods. The method is particularly applicable to resurfacing of existing porous tennis courts with an artificial turf surface.

Accordingly, there is provided a method of resurfacing an existing porous surface on a non-porous base ₀ having drainage means with an artificial turf surface which comprises laying an intermediate material over said existing surface and thereafter substantially flatly laying an artificial turf over said intermediate material.

Interposed between the turf and the base, the _ς intermediate material enhances drainage of the water or provides additional resilience to the surface, or both. Preferably the intermediate material and the artificial turf are individually or separately fixed to said existing porous

surface by way of fixing pins or pegs passing through the material and the turf into the existing surface.

Preferably any marking lines of the existing porous surface are removed and the playing surface levelled as required prior to the laying of the intermediate material and the artificial turf to ensure the latter is substantially flatly laid.

Depending on the relative porosity of the existing porous surface it may be necessary to provide a new drainage system in the existing porous surface to ensure that water falling on the artificial turf surface is adequately drained away. Preferably this can be achieved by first forming drainage trenches in the existing porous surface in a suitable pattern or configuration to drain water from the porous surface to an appropriate storm water or other waste water drainage system, inserting in said drainage trenches suitable drainage medium and then laying the intermediate material and the artificial turf over the existing porous surface.

Preferably the drainage medium comprises a material dimensioned to conform closely to the dimensions of the drainage trenches. The material should permit water to percolate through the material to the base of the drainage trench and away to the storm water or waste water drainage system. One preferred such material comprises a convoluted semi-rigid synthetic plastics material which has some structural strength but can be formed in lengths of constant cross-section but be deformed or deviated along its length. That is to say, the material is capable of being bent slightly from a straight line to allow for slight deviations in the line of the drainage trench in which it is to be placed. The convoluted plastics material may be in the form of a randomly packed tape of plastics material formed into a length of constant cross-section. The material is preferably encased in a sleeve of geotextile material.

Alternatively, the drainage medium is formed of a plurality of strips or plastic material sheet deformed (in the manner of an egg carton) alternately in one direction

and then another such that adjacent deformations are in opposite directions. Strips of this material are also contained singly or in groups within a sleeve of geotextile material. The plastics material may be any convenient material such as polyethylene, polypropylene or the like.

One example of the intermediate material interposed between the turf and the base is a material which comprises a "trellis-like" formation of synthetic plastic material laths or slats. Preferably this material comprises at least two layers of synthetic plastic material laths or slats

10 disposed in criss-cross fashion one on top of the other with the laths or slats of one layer being at approximately right-angles to the laths or slats of an adjacent layer.

The cross-sectional configuration of individual laths or

15 slats may be of any convenient shape and be substantially uniform, but not necessarily completely uniform in cross-section. A purpose of the intermediate material is to provide a series of channels between the laths or slats of the lower layer adjacent the base, to direct water towards the drainage means such as slots, holes or trenches formed

20 in the base to facilitate efficient drainage. The intermediate material is therefore laid on the base such that the direction of the laths or slats or channels of the lower layer criss-cross with the drainage means formed in the base. The intermediate material may include, on its

25 upper layer or between its upper and lower layers, in the case of two layers, a layer or layers of a geotextile material to act as a filter to reduce the passage of particulate matters through the intermediate material and to

30 the drainage means which could otherwise become blocked or reduced in drainage efficiency by such matters.

_ In order that the invention may be more readily understood, preferred forms of turf surfaces according to the invention and a particularly preferred method of i _b_ resurfacing existing surfaces will now be described with reference to the accompanying drawings.

Figure 1 is one preferred form of the surface constructed in accordance with the invention shown in schematic partial perspective;

Figure 2 shows a portion of a tennis court, for example, resurfaced in accordance with the method provided by the invention.

Figure 3 shows an alternate form of drainage means for a surface according to the invention; and

Figure 4 shows yet another form of surface in accordance with the invention.

Referring to Figure 1, the playing surface 10 comprises, in the simplest embodiment, a base 11 of reinforced concrete material having a flat level upper surface 12. Drainage slots 13 are formed in the base 11 sloping from a point 14 at some point within the playing area of the playing surface, downwards to a drain 15 at some convenient point within, off or outside the playing area of the playing surface 10. A geotextile material 16 is disposed over the base 11 which is then covered by an artificial turf material 17 which may be in the form of a carpet of tufted synthetic or other suitable materials which may then be "sand-filled" as is known. The geotextile material 16 serves as a filter to prevent fine sand particles, or at least reduce the amount of fine sand particles from passing through to and reducing the efficiency of, drainage slots 13. It may be necessary to fix the material or materials to the underlying surface by means of adhesives or other fixing means such as pins, staples or rivets.

In a particularly preferred embodiment of the invention, there is disposed between the geotextile material 16 and the base 11, a plastics lattice material 18. The plastics mesh material 18 comprises two layers 19,20 of synthetic plastics material laths or slats disposed in criss-cross fashion one on top of the other with the laths or slats of one layer being approximately at right-angles to the laths or slats of the adjacent layer. It will be seen that water passing from the turf to the base passes through this lattice material 18 and is directed, by channels formed between the individual laths of the lower layer 20, towards the drainage slots 13. In an alternative arrangement, the

plastics lattice material 18 is covered by a further layer 21 of geotextile material on its upper surface. Additionally, a further layer of geotextile material 22 may be applied to the bottom surface of the plastics lattice material 18. The lattice material is not woven, but formed by bonding the upper and lower layers of laths or slats in a suitable manner. As described, the lower layer 20 then rests directly on surface 12 of base 11 and forms channels which can direct water falling on the playing surface towards the drainage slots.

In another preferred embodiment, a reinforced non-woven acrylic needle punched "felt" or other suitable fibrous material; for example, FILTRAM (Registered Trade Mark), is used in place of or together with the lattice material. It is appreciated that this intermediate material interposed between the turf and the base must lay substantially flat and must not cause any waves or ripples to form on the playing surface.

The slots 13 may be formed in the base 11 during construction or by means of a concrete saw after construction of the base. The slots are typically from about 2 to 6 millimetres in width but may be greater, and extend from any convenient point or points within the playing area to suitable drainage points either within or beyond the normal playing area covered by the turf.

Preferably, synthetic mesh material is placed on the surface 12 of base 11 to cover the slots 13 thus providing support to and stopping the turf material from sagging into the slots 13. The synthetic mesh material must be of relative dimensions of the slots, typically 2.5 millimetres and conveniently adhesively placed on the base.

It will be seen that the inclusion of the plastics mesh material 18, in addition to providing assistance in drainage of the turf material 17, provides additional resilience to the synthetic turf playing surface thus tending to reduce player fatigue and/or the likelihood of injury. Further, the provision of the plastics mesh material 18 represents a novel method to resurface existing grass surfaces with artificial turf surfaces.

Referring to Figure 2, there is shown schematically and in cross-section alternative preferred resurfaced playing surfaces 110 in accordance with the invention. The "surface" which includes the drainage means of the surface includes an artificial turf material 111 as is known in the art, laid over an intermediate layer 112. This intermediate layer 112 is likewise comprised of a trellis-like material of a plastics mesh material comprising a plurality of synthetic plastics material laths or slats 113,114 disposed over the entire existing surface 115 being resurfaced.

Preferably the plastics mesh material is provided with a backing (not shown) of a suitable geotextile material either between the intermediate layer 112 and the turf material 111 and/or between the intermediate layer 112 and the existing surface 115. It may be also that the geotextile material may be incorporated between the layers of laths or slats 113,114 of the intermediate layer. The laths or slats 113,114 of the intermediate layer may be formed in the same way as those described with reference to Figure 1. The layers of laths or slats 113,114 are preferably formed by appropriate methods as are known and are integrally formed to provide distinct layers of laths or slats such that there are a plurality of channels 116 formed between successive lower laths or slats 114 and maintained in spaced relationship one with another by means of their attachment to the upper laths or slats 113. Further, should the condition of the existing playing surface 115 so require, stepped drainage trench 117 may be formed in the surface 115 to encourage drainage of water from point A to point B. The trench 117 terminates in main drainage trench 118 in which a suitable standard drain may be disposed. The stepped drainage trench 117 is preferably filled with individual draina e means 119, 120, 121 of varying sizes according to the stepped depth of the trench 117 at a particular point. The drainage means 119, 120, 121 comprise a convoluted plastics material as previously described. • The convoluted plastics material permits water to percolate to the bottom of the trench whilst the geotextile material prevents entry

of most materials which would otherwise reduce the efficiency of the drainage system by, for example, sedimentation. The drainage means 119, 120, 121 may be of standard sizes as for any other size as may be appropriate for the purpose.

Once such drainage means has been installed in the surface, the surface is levelled as is necessary and compacted as required. The intermediate layer is then laid and fixed to the surface by suitable pegs (not shown) which pass through the material and into the underlying existing court surface. The synthetic grass surface may then be laid over the intermediate layer and again fixed with sufficient pegs as is deemed appropriate.

In an alternative construction, shown to the left of Figure 2, the intermediate layer 123 comprises a grid of plastics material comprising a plurality of members 124 and cross members 125 disposed at approximately right angles and in the same plane. Once this intermediate layer is fixed to the surface as previously described with or without inclusion of a geotextile layer above or below the intermediate layer 123, the artificial turf surface 126 is laid as previously described.

Referring to Figure 3, there is shown a cross-sectional view of a modified form of playing surface 20 including base 21 and artificial turf (and other intermediate layers) 22. The drainage slots 23 direct water to drain 24 off or outside the playing area of the playing surface. Other slots 25 are cut to slope towards additional drain 26 embedded in the concrete material of base 21. The formation of the slots 25, by way of concrete saw, would also form appropriate slot 27 in the drain to allow entry of water to the drain. The drain 26 may be of any convenient material, such as, polypropylene pipe or other _^ readily available suitable material. Referring to Figure 4, there is shown a further embodiment of the invention, again in cross-section, wherein the playing surface 30, as previously includes a concrete base 31 and an artificial turf (and other intermediate

layers) 32. The concrete base 31 is formed with surfaces 34 sloping towards a central drain 33. The flat level base surface 36, on which the turf 32 is to be laid, is formed by placing, within the hollow or void 37 so formed, of moulded synthetic plastics materials formwork 35. This formwork 35 is designed to rest on surfaces 34 and includes drainage slots 38 in the upper face thereof to permit flow of water therethrough to sloping surfaces 34 and thus to drain 33.

The formwork 35 may be of any convenient configuration to suit the purpose for which it is to be used.

10

Whilst the invention has been particularly described with reference to artificial turf surfaces, it is equally applicable to the formation of a surface using natural turf which may be laid as is known in the art in

,_ place of the artificial turf described above. 15

It will be seen from the foregoing, that a flat sloping or flat level surface, particularly a playing surface, may be constructed which may be used in outdoor situations without the problem of formation of excess surface water areas due to the drainage system incorporated in the turf surface of the present invention.

Whilst a preferred method of resurfacing an existing porous surface is described hereinbefore, it will be readily apparent to those skilled in the art that many

- - modifications may be made to the invention as described with reference to the preferred features of construction and the preferred method without departing from the spirit of the invention disclosed herein.

The method of the invention is particularly suited

_ ₀ to resurfacing an existing brick dust or en-tout-cas tennis court surface with an artificial turf surface such as sand filled synthetic grass surface.

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