Event organisers and clubs seeking to protect grass surfaces from rutting or erosion due to heavy use often find a sound solution in turf reinforcement products. Generally, the reinforcement systems consist of polyethylene meshes that are rolled out over cut grass and then pinned to the surface or cell structures that go into the grass.
Keeping the ground porous but durable, they also help to retain the natural aesthetics of the area. These systems are often preferred to hardstanding, which speeds up the flow of water into rivers and can contribute to local flooding.
Selection of the most suitable product depends on a variety of factors, including the softness of the ground and whether it is required for temporary or permanent use. The appeal is the fact that the grass can withstand much heavier use, with very little disruption to the site during installation.
It is important to stress that turf reinforcement systems will not overcome areas liable to flooding or that hold water - here, remedial drainage work is often the only solution prior to installation.
For pedestrian safety, some systems cannot be used until the grass has grown through because this helps to ensure that the reinforcement is thoroughly secured and the surface less slippery. When immediate pedestrian access is required, a geotextile covering is often recommended because it does not become muddied from frequent use.
Where local authorities, large estates or clubs are looking to provide overflow parking, vehicle and pedestrian tracks, cycleways, stabilisation of grass verges, soil-erosion protection or disabled access routes, turf reinforcement systems ensure that the grass is strong enough to cope.
Tenax UK offers a range of products including GrassTrack, which can provide temporary access over muddy ground, making it ideal for use at outdoor events, concerts and exhibitions. An added advantage is that each GrassTrack roll, which is 1.9m wide by 20m long, can be hosed down after use, rolled up and re-used.
Providing dual-purpose use for either vehicles or pedestrians, when the black geotextile is on the ground, with the 15x15mm high-density polyethylene green mesh on top, the system allows access by cars and lightweight vans.
Alternatively, for safe and clean pedestrian access over turf, GrassTrack can be laid with the geotextile at the top. Quick and easy to lay, the product is simply secured to the ground by U or J fixing pins.
Based in Essex, Perfo supplies tiles specifically designed to be top-applied. All are made from recycled plastic, thereby offering an environmentally-friendly solution.
Tiles are clipped together on top of the grass and then compacted in using either a roller or rammers.
Perfo sales director Chris Barcus says: "This makes our system different from other grids on the market, which are usually designed to be buried."
He adds: "For many overflow-parking projects, installation costs and time are key factors, often dictating whether or not the project will be feasible. Our tiles can be installed quickly and driven on as soon as they are pressed into the ground."
For softer ground and applications where vehicles will be manoeuvring, the company supplies Perfo-AK Anchor tiles. With a semi-enclosed top structure, this prevents the resurgence of mud from below the tiles. The 300x300mm tiles have a deeper profile, which means they are compacted some 75mm into the grass for good stability.
Secured by large ground anchors, the surface will withstand heavy loads up to 60 tonnes per square metre, depending on ground conditions and preparation. Perfo tiles are UV and frost resistant, and resistant to oil, solvents, salt water and most acids. Non-perforated white tiles for marking purposes, such as parking bays, are also available on request.
Preparation includes cutting grass as short as possible and levelling out undulations using topsoil or a sand/soil mixture. The ground should be soft enough to ensure that the sections can be compacted into the surface easily and completely.
Carpettime reports that the majority of its turf reinforcement products are supplied to landscape gardeners. The company's Turf Reinforcement Mesh can be used by pedestrians or wheeled vehicles. It should be installed a few months prior to planned use, enabling the grass to grow into the mesh to help establish a stable surface.
The polymer mesh is simply rolled out and laid on top of the cut grass and secured with metal or plastic pegs. Alternatively, if a new area is being created, it can be incorporated at the laying/grass-sowing stage. This mesh binds with the grass to create a protective layer beneath the surface, and can also be used to provide a permanent solution to reinforcing grass verges and embankments.
Also available from Carpettime and three to four times as thick as the reinforcement mesh, Grass Protection Mesh is a heavy-duty polyethylene grid with an open structure, allowing grass to grow through and water to drain away.
The wavy structure provides increased traction and a slip-resistant surface, making it ideal for car-parking and tracks.
The standard product is 11mm thick and will support vehicles up to 7.5 tonnes - the 14mm-thick premium will withstand eight tonnes per axle imposed load.
For optimum results when sited in a permanent location, the grass should be allowed to grow through and intertwine with the mesh for several weeks. However, this product can be driven on immediately for temporary parking.
Offering permeable ground reinforcement solutions across a wide range of applications, Gridforce has a choice of five paver options. Manufactured from low-density polyethylene, they provide high compressive strength combined with flexibility and resilience.
The pavers can be used in temperatures as low as -35 degsC and as high as 85 degsC. Uses include footpaths, car parks, tree-root protection, grass-verge reinforcement and emergency fire access routes. The product is normally laid on a free-draining stone base, eliminating the requirement for pipework and returning storm water to the water table. Depending on ground conditions, a reduced-dig or no-dig solution may also be offered.
This interlocking system eliminates the need to pin the pavers together, and they can be easily cut with a hand or power saw. The cells can be filled with stone or soil, and then grass seed sown.
Strengthening grass paths
At the sensitive site of Burgh Castle, south west of Great Yarmouth, Tenax GP-Flex 1800 was used to protect and reinforce grass paths.
Tenax UK consultant Keith Barsby says: "This project was successful because the right mesh was chosen for the job. Good installation is also paramount and Giles Landscapes did a really good job."
The grass was cut and the ground levelled with a 50/50 mix of sharp sand/soil before a grass seed mix was applied. GP-Flex was then rolled out, fixed by metal pins and covered with a layer of sharp sand/soil.
Each roll is 2x20m and the bicoloured green-and-brown flexible material allows easy installation. The grass quickly established through the mesh to provide a stable surface for pedestrian and wheelchair access.
For optimum results, the company suggests laying in early spring to early autumn. This allows the grass to grow through and the root mass to establish and interlock with the mesh filaments.
Importantly, it is ideal for use at visitor attractions because the system is slip-resistant and, with its high-tensile strength, can cope with the machinery likely to traffic these areas.
Grass seed selection
Together with the most suitable reinforcement material, grass seed is a vital element to consider.
Where severe stress is placed on the leaf structure, the mixture recommended by Rigby Taylor, which supplies Top Green seed, is 20 per cent hard fescue, 25 per cent chewings fescue, 25 per cent slender creeping and 25 per cent strong creeping red fescue and five per cent browntop bent.
Chewings provide the tufted density, with the bent creating a sound rhizomatous base. This sward is dense with good year-round colour.
For verges and picnic areas, the company suggests perennial ryegrass should make up 45 per cent of the mix, with 35 per cent slender creeping and 20 per cent strong creeping red fescue. Providing rapid establishment, this mixture is hard-wearing.
Year-round parking for council
Southend Borough Council selected GrassProtecta supplied by Fiberweb Geosynthetics for its East Beach car park to strengthen grass subject to wear and rutting.
The council needed a product that would eliminate these problems and maintain a natural grassland finish. This project also needed to be sympathetic to the coastal surroundings.
Ruts were levelled with soil and seeded. Rolls of green GrassProtecta (Heavy) were laid out to relax then cut to size prior to pinning. It is supplied in 2x20m or 1x10m rolls made from partly recycled UV-stabilised polyethylene polymer.
Regular watering ensured that the existing sward and newly-sown seed established through the mesh within weeks. This created a strong intertwined surface layer ready for use as a car park.