On Existing Grass
The existing grass needs to be removed, to a depth of 40 mm, or to the depth of the existing roots. The ground should be levelled and any soft spots filled with hardcore. The ground should be excavated to allow for the correct depth of construction so the grass finishes so the fibres are 20 mm higher than the finished surfaces edges.
Once the formation layer is firm, spread, level and compact 35 mm of sharp sand to the desired gradients. If the formation layer is ‘boggy’, more excavation and a 100 mm layer of hardcore maybe required. Please note that if the area to be surfaced is in a hollow, and the water doesn’t drain away, the addition of AGD grass and sand layers may not solve the drainage problem.
If laying artificial grass over tarmac playgrounds, or tarmac tennis courts you should fill any hollows with sand and cement. Remove any large weeds and if necessary spray the weed with a total trans-located herbicide. Artificial Grass can be laid directly over tarmac and fixed at the edges. When laying artificial grass over tarmac the grass can feel hard, so to avoid this a 10 mm shocksafe Play pad is laid under the artificial grass. This also helps rapid surface water drainage.
When laying over tarmac you will often come across inspection chamber covers, which will require access. We have several choices here, cut around the steelwork, exposing the cover. Stick grass to the cover (could peel off), cover the chamber and temporary fix the ground to the edges of the site, so the grass can be rolled back to gain access. With regards to standing water, sometimes it is possible to drill the tarmac 30-50mm diameter at one metre centres, backfilling the holes with pea shingle. (porosity of the sub base must be checked before drilling)
On Roof Tops
Often roof tops have water proof barriers that cannot be fixed to. The recommended way to fix artificial grass to roof tops, is to weigh it down. We do this by spreading 10 kg /m2of silica sand into the pile of the grass. Certain roof systems will require a separating membrane between the artificial grass and the waterproof system, we often use a geotextile membrane. (Terram 1000 or similar)
Over Existing Wet Pour
Artificial grass can be laid directly over existing wet pour. Any hollows or deep cracks should be filled with rubber crumb and binder. The perimeter of the artificial grass can be fixed using one of the various options.
Over Steep Mounds
Mounds should be constructed from MOT type 1 crushed stone shaped, levelled and compacted in 150 mm layers.
The surface of the stone should be covered in a 50 mm depth of C25 concrete screed, smoothing the concrete to gradual slopes.
Critical Fall heights on mounds – It is not possible to wrap a curved mound in shockpad to provide an overall enhanced critical fall height. Areas where a CFH is required should be designed to accept flat sheets of shock pad with a very gentle one dimensional curve at most. These areas can still be sloping.
Over Steep Slopes > 30 degrees
The existing grass should be removed, to a depth of 40 mm, or to the depth of the existing roots. The ground should be levelled and any soft spots filled with hardcore. The ground should be excavated to allow for the correct depth of construction so the grass finishes with the fibres 20 mm higher than the finished surfaces edges.
Once the formation layer is firm, spread, level and compact 35 mm of sharp sand to the desired gradients. If the formation layer is ‘boggy’, more excavation and a 100 mm layer of hardcore maybe required. If the slopes are steeper than 30 degrees, the sand layer may migrate down the slope. To avoid this, screed the slope with a week sand and cement mix (1:6), please note that the sand and cement screed will negate the critical fall height qualities.
It is essential that steep slopes have the timber anchor edge detail at the top of the slope. See ‘edge details’.
Artificial grass can be installed over decking. If the decking is laid with large gaps over 10mm, an additional shocksafe Play pad should be laid to bridge the gaps. The artificial grass can be fixed to the edges with 30 mm galvanised clout nails at 100 mm centres
It is very important that tree roots are not damaged and that the environment around the tree roots remains the same. Some trees have tree preservation orders (TPO’s) on them, so it’s critical the tree roots aren’t damaged which may affect the health of the tree. We would advise that when excavating around tree roots, photographs are taken at the various stages. There should be no significant alterations in levels (no greater than 100mm) and the surface material should be permeable to allow gaseous exchange and water to permeate through to the roots.
Artificial grass can in many cases be laid up to the base of the trunk and tacked down using small galvanised flat head nails.
Neil contacted The New Driveway Company because he wanted a new patio and artificial lawn area next to his hot tub.
New block paving driveway, gravel car park, Indian Sandstone patio for Ella and Sam in Wantage, Oxfordshire.
“They were punctual and worked tirelessly to complete the job.”
New permeable block driveway and installation of artificial grass.