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Grass Pavers

by editor

Long gone are the days of the quarter acre block of land where mowing the property took our valuable weekend time away from us. These days grass is a landscape feature. House blocks in new suburbs around Australia average 500sqm and in that space we have a house, we sometimes have a swim spa/swimming pool in the backyard together with an outdoor entertaining space.

In the front yard we are lucky if we have a garage for storage and the jet ski/pushbikes. Sometimes, we also have room for the boat/caravan. The lawn and driveway provide multiple car spaces and the lawn is ruined in the process.

Why lay a front lawn I hear you ask?
Councils require homebuilders/homeowners/commercial sites to have certain percentage combinations of hardscape and softscape for each property under its jurisdiction. The good news is that landscapers can install plastic permeable grid pavers for homeowners which are incorporated into grass so pedestrian and vehicular traffic can use it with little damage to the surface. Permeable grid pavers are designed to reinforce the ground they’re set into, giving the ground enough strength for it to be used as a driveway without incurring any damage from traffic.

They create cleaner urban spaces allowing rain and stormwater to infiltrate through infill gravel or grass to be detained below, reducing pollutants, promoting water quality, tree health and better urban environments.

The storm water passes through the load bearing surface and aggregate subbase that is selected, based upon the intended application and required infiltration rate. Runoff is stored in the stone aggregate subbase course/storage layer and allowed to infiltrate into the surrounding soil (functioning like an infiltration basin). Similar systems have been used in Europe for over 40 years so they will last for decades, and the better ones are made from recycled plastics.

The effective infiltration rate for the watershed can be changed by trapping the water in differing permeable layers and effectively changing the time of concentration in the catchment area.

One such Australian manufacturer and supplier in Queensland of an American designed product is TRUEGRID (www. truegridpaver.com.au), which is a honeycombed 3D grid-cellular system, made of 100% recycled HDPE plastic.

Rural areas often have muddy horse stables, which can now be replaced with permeable grid paving. They allow urine to drain and keep stables from becoming muddy and rutted.

More good news… because landscapers offer discounts for large volume jobs, it’s an opportunity to quote for the backyard as well so that the homeowners’ kids and dogs can run and play on the grass anytime, especially in ongoing wet conditions like we have recently experienced in many parts of Australia. An added bonus it that permeable grid paving stabilises soil, which in turn contributes to the healthy growth of lawn provided we use a sandy soil loam mix.

Businesses are preferring this method of creating trafficable areas because they can increase their building footprint on land saved by eliminating or reducing detention pits/ponds/basins and get a 100 per cent pervious drive-on surface with long-term, cost-effective benefits. Total costs are less than concrete and comparable with asphalt. Being able to park heavy vehicles, including coaches without damaging lawn, is hugely important for businesses wanting to add to or change the layout of parking spaces. One-hundred and fifty tonne is the maximum load, which is more than sufficient for most uses. Snow melts faster on the grid and there is less ice build-up. It can be easily ploughed, snow-blown or shovelled.

Another phenomenon not often addressed is the Urban Heat Island Effect, which occurs in cities and industrial sites that have consistently higher temperatures than surrounding areas because of greater retention of heat. This retention of heat is due to buildings, concrete and asphalt. Permeable Grid paving filled with gravel or grass reduces the absorbability of solar rays and thus helps cool the natural environment.

Another Australian supplier of this technology is www.geohex.com.au. The company uses 100% recyclable plastic in its manufacture; the product is totally non-toxic to humans, animals and plants; it can be laid in any weather; it can be cut to size; each piece nests neatly for efficient storage and transportation; its non-reactive to solvents, oils, chemicals and water; installation of it markedly reduces any maintenance costs; and it lasts for decades.

It’s worth noting that many councils in each state require approximately 15 per cent of a commercial property to be softscape. Detention basins cost thousands of dollars, but when you don’t have runoff because of the absorption of a working grass or other type of pervious paving system, you do away with the need for this big expense.

A leading supplier in NSW is www.grassreinforcement.com.au. If configured efficiently, rain will infiltrate the surface at over 20m/hr and there is no runoff. Generally speaking, 3D grids of grass paving are suitable for slopes of less than 11 degrees in gradient.

A large supplier of concrete grass pavers called TURFGRID with numerous distribution points in SA is www.australianpaving.com.

Crucial to your choice of material is its ability to provide a stable and continuous load-bearing surface throughout parking/ pedestrian areas.

Permeable concrete paving blocks, which have been available for years, are an option and grass works well with them.

Please note: Permeable paving is not recommended for slopes. Why? Water will only fill the pavers to the lowest elevation of the surface, and on a slope it could exit the paver through the lower end.

So, we grade the proposed site, lay a gravel of a size and a subbase to a depth determined by the future load, compact it, in need, we install Geotech fabric for any water pollution issues, edging restraints and irrigation.

Next, we spread a 30mm – 50mm layer of root zone mix consisting of sandy topsoil (70% coarse sand to 30% screened topsoil) over the base course layer and screed to level, but do not compact. Then place down our grass pavers (in the chosen style) and backfill the grid with a sandy soil loam mix for grass or groundcovers, or aggregates for commercial sites to save on any maintenance costs for many years. Please note: any aggregate mix should be plate compacted before use.

If installing grass pavers fill the panels with the same root zone mix as used for the bedding layer to 10mm above the top of the panels for consolidation. Use a plate compactor to consolidate the filling material into the pavers. Fill any voids that show due to this process with more root zone mix and leave filling material flush with the panels.

Broadcast the grass seed and add a light top dressing to provide adequate germination conditions.

Hydro seeding the area is a good option if your site is an acreage property, has uneven slopes or will benefit from erosion, dust, and/ or weed control. The hydroseeding process is used to plant seeds in a slurry or wet mixture of mulch, fertiliser, water and other soil amendments which we normally wouldn’t bother with. Better still, the mulch used in hydroseeding is heavy enough to weigh down the grass seed and create a protective blanket for all seasons as they germinate.

Grass-Cel www.grasscel.com) has been manufacturing its weight bearing porous paving blocks in Australia for over 40 years and continues to distribute them to all states of Australia. More good news… it’s 100% Australian owned and manufactured, it is the only product of its kind certified by Good Environmental Choice Australia. The company’s mission is to become the go-to source for sustainable paving and driveway systems. Do yourself a favour and check out their projects.

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