This invention concerns a recreational surface for games such as soccer and hockey for example and also horse-racing tracks for example.

The conventional surface for such activities as mentioned above is turf. Normal turf, whilst highly satisfactory under ideal conditions does have some serious disadvantages. In dry seasons or times of drought it can become very hard with risk of injury to falling players. In wet seasons it can become waterlogged making it unpleasant to use and very susceptible to damage. In very cold conditions it can become frozen and again hard and injurious.

Ideally a grass recreational surface for these purposes should be compliant under all conditions and never excessively dry or waterlogged.

It is an object of the present invention to provide a recreational surface of grass which overcomes the problems associated with conventional turf.

According to the present invention a recreational surface comprises grass growing on a coherent layer of compliant material having substantial voidage therein,

the roots of the grass penetrating the interstices thereof, and a free-draining substrate supporting said layer.

The layer may have a topping of particulate material, such as of sand or loam or a mixture thereof. This layer may have a thickness of up to 10 cm.

A bed of root-growth medium may be provided between said layer and the substrate. This bed may have a thickness of between 5 and 20 cm for example.

The layer may comprise rubber crumb bonded together with a suitable binder and may have a thickness of between 1 and 10 cm for example.

The binder may be a polyurethane resin.

The topping may be a filter sand and may have a thickness of 2 cm for example.

The grass may be grown from seed sown onto the layer or topping or provided by turves laid on the layer or topping.

The grass may be a perennial rye-grass or fescue.

In dry areas or areas prone to drought, a water retaining layer having distributed excess water drainage means may be provided above the substrate.

The water retaining layer may be defined by a layer of material from which water would ordinarily drain but supported on a water retaining membrane.

The layer of water retaining material may be said compliant material or said bed of root growth medium.

The water retaining membrane may comprise sheet material formed as a base layer with surrounding containment and distributed, elevated drainage means. The sheet material may be formed as a compartmented layer with compartments having a base and surrounding upstanding walls perforated above the base layer to form said drainage means. The sheet material may be of a plastics material such as polypropylene.

The membrane may on the other hand be formed in situ as by concrete construction, or may comprise sheet material draped over a prepared base with distributed, upstanding means perforated to provide the drainage means.

The water retaining membrane may be in the form of trays.

The water retaining layer may be a layer of water absorbing and retaining material such as peat, and this may comprise the bed of rooth growth medium.

The water absorbing and retaining material may be provided in the form of pre-formed plates of circular or other shape such that when laid in abutting relationship spaces therebetween can be filled with a material through which water can drain to form the excess water drainage means.

The water absorbing and retaining material may be located in trays having upstanding side walls.

The excess water drainage means may be provided in the walls of the trays at the top of the layer of water absorbing and retaining material.

The trays may be of rectangular shape having inwardly directed quarter-circular formations at their corners extending from the tray base to the top of the layer of water absorbing and retaining material and opening into the upper part of the tray whereby when four trays are positioned with abutting corners small stand- i es are formed.

There may be drainage holes in the base of the trays

Embodiments of recreational surface according to the invention will now be described with reference to the accompanying drawings, in which :-

Figure 1 is a cross-section through a first embodiment;

Figure 2 is a cross-section through a second embodiment;

Figure 3 is a section of the line III-III of Figure 2;

Figure 4 is a cross-section through a third embodiment;

Figure 5 is a section on the line V-V of Figure 4;

Figure 6 is a cross-section through a fourth embodiment;

Figure 7 is a section on the line VII-VII of Figure 6;

Figure 8 is a section like Figure 1 of a fifth embodiment;

Figure 9 is a cross-section through a sixth embodiment;

Figure 10 is a section on the line X-X of Figure 9;

Figure 11 is a cross-section through a seventh embodiment;

and Figure 12 is a section on the line XII-XII of

Figure 11.

In the first embodiment, there is a self-draining substrate comprising crushed stone 1 incorporating drainage pipes 2. This substrate supports a bed of root-growth medium 3, a coherent compliant self-draining layer 4 having substantial voidage therein and formed from rubber crumb, of 4-8 mm diameter bound by, say, 5-10% of a resin such as polyurethane or epoxy. The rubber crumb may be spread out after wetting with a liquid polymer and a catalyst, or a liquid catalyst may be spread over the crumb surface initially wetted with polymer to pass through the interstices to effect polymerization to join the crumbs into a coherent but compliant mass having substantial voidage therein.

Above the layer 4 is a topping 5 of filter sand or loam or mixture thereof which supports a grass surface 6 provided by sowing or turves. The roots of the grass penetrate the interstices of the layer 4.

Common to all embodiments remaining to be described is the provision of a buried water retaining layer with excess water drainage means.

In the embodiments of Figures 2 to 8, the water retaining layer is comprised by material through which water would ordinarily drain but supported on a water retaining membrane.

The membrane 11 comprises, in the embodiment of Figures 2 and 3, a sheet material of for instance polypropylene, which has been formed into a compart- mented layer with compartments 13 having a base 14 and surrounding upstanding walls 15 perforated at 16 above the base layer to form the drainage means 12. The upstanding walls 15 form containment for the water.

Such a compartmented layer could be assembled from moulded stiff sheeting and produced in pieces of any convenient size and laid out side by side to cover a large area such as a football or cricket pitch or a track such as a horse racing or athletics track or a

tennis court. There is no need to join or seal the edges together - adjacent pieces can be laid in abutting or overlapping fashion as desired - the joints will be arranged at the level of the top of the walls 15 and any gaps will simply represent additional excess drainage.

The membrane 11 is overlain with a coherent open cell, water permeable layer 17 which is compliant and which comprises rubber crumb e.g. of 4-8 mm diameter bound by, say 5-10% of a resin, such as polyurethane or epoxy. As illustrated, this mass extends above the performations 16 and tends to protect the same against becoming blocked over time.

The membrane 11 is laid on a mechanically stable and water permeable substrate 18 which comprises blinded stone and which includes piped drainage 19.

A topping 21 of planting medium which may comprise or include a substantial proportion of filter bed sand is spread over the layer 17, and sown with grass or laid with turf.

Such an arrangement affords an excellent sports surface which is not subject, or at least less prone than conventional sportsfield surfaces, to overall waterlogging and uddiness resulting from rainfall and

occasioned by poor drainage, or local waterlogging and consequential muddiness in high foot traffic areas, such as golf tees and goal mouth areas, which is due to soil compaction forming an impermeable mass. The new surface is resistant to excessive hardness due to baking of soil in hot, dry weather or by sub-soil bound water freezing during cold weather. Prolonged dry spells and excessive drainage and consequent lack of water retention no longer affect the surface, which is resistant also to loss of ground cover even under very heavy usage.

It will be seen that the arrangement is such that water is retained - even in dry weather, applied water does not all simply run to waste - but excessive water retention which would result in waterlogging is prevented.

Water trapped in the compartments 13 is available directly to the roots of the grass or indirectly through capillary action through the layer 17 into which the roots of the grass penetrate.

The configuration may be adapted to local conditions. In a hot, dry climate the ratio of water- retained volume to drainage rate is desirably high, while in a wet climate it is desirably low. This can be adjusted by designing wider and/or deeper trays and more or less drainage apertures.

Figures 4 and 5 illustrate a different arrangement in which the drainage means are provided in the form of concrete or plastic mouldings 31 which are simply distributed atop a blinded stone or hardcore sub-base 32 and overlain with a flexible plastics material sheet 33 constituting the membrane 11. Where the sheet covers the apertures 16 in the mouldings 31 it is perforated and may be retained by hammering in a close fitting pipe section 32. This arrangement is not compartmented and it may be desirable to incorporate a surrounding wall or simply raise up the edges of the sheet 33.

Figure 6 shows an arrangement in which the membrane is provided as a concrete layer 51 with emplaced mouldings 52 analogous to the mouldings 31 of Figures 4 and 5. Figure 7 shows this effectively in plan and illustrates also a surrounding retaining wall 53. Figure 8 shows an arrangement in which a concrete layer like layer 51 of Figure 6 and 7 has crossing ridges 71 which compartmentalize the arrangement and are provided with upper drainage holes 72.

In all the embodiments described thus far, a bed of sand or sandy soil or other root growth medium may be disposed between the layer 17 and membrane 11 as indicated at 60 in Figure 6.

In the remaining embodiments to be described the water retaining layer is comprised by a water absorbing and retaining medium.

In the sixth embodiment shown in Figures 9 and 10 the water retaining layer is comprised by pre-formed discs 110 of peat which are laid on a suitable substrate, such as crushed stone 111 incorporating drainage pipes 112 therein, in abutting relationship. The spaces between the discs 110 are filled with a material such as sand 113 through which water may readily drain into the substrate.

The water retaining layer is overlaid by a resilient permeable layer 116 which may be comprised by resin bonded rubber crumb for example as described above and a growing medium 114 such as soil or sand. The soil or sand is sown with grass 115 or the soil may be provided by turves.

In the seventh embodiment shown in Figures 11 and 12, the peat 110, growing medium 114 and permeable resilient layer 116 are disposed in trays 120 of plastics material.

The trays 120 are of square or rectangular shape and may be set down -onto any suitable substrate such as

that described in connection with the first embodiment. Excess water drainage means is provided by inwardly directed quarter-circular formations 121 at the corners of the trays 120 extending from their bases to the top of the peat layer and opening into the upper part of the trays. It will be understood that when the trays are positioned on the substrate with their corners in abutting relationship small stand pipes extending from the substrate to the top of the peat layer are formed.

The trays 120 have small holes 122 in their bases for additional drainage.

The trays are planted with grass and provide means for laying (in the fashion or carpet tiles) a turf surface onto a prepared substrate. Damaged areas of turf as on a golf tee-ing ground for example can be lifted and replaced. The lifted trays can be laid elsewhere for repair.

It is anticipated that in all the embodiments the grass surface will be "self-healing" in that even quite serious surface damage will not destroy the root matrix within the rubber crumb.

It will be appreciated that it is not intended to limit the invention to the above example only, many

variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof as defined by the appended claims.

Thus, for example, grass seed may be sown onto the surface of the rubber crumb and a sand dressing applied after germination.

Again, for example, the rubber crumb layer may include additives such as fertilizer and a rooting compound.