What Is Permeable Paving and How Does It Work?
As the name might suggest, permeable paving is a type of paving that allows rainwater to seep through to the ground below. Fresh, clean water soaks back into aquifers and groundwater supplies having been filtered as it passes through. An environmentally responsible choice, permeable paving stops the rainwater from draining off into stormwater drains or onto your neighbour’s properties.
How permeable paving works
Permeable paving is porous, meaning that instead of water pooling on top of or running off your pavers, water seeps through. Water percolates, such as it would in a coffee pot, through the paving to a cleansing layer of gravel. The gravel then acts as a natural filter, clearing the water of pollutants.
Permeable paving works by handling rainwater and reducing the pressure on ageing, overloaded drainage systems. It does this in two ways, either by helping rainwater to disperse quickly into the ground or by holding onto it and letting it seep out gradually.
Why is permeable paving needed?
During periods of dry weather, heavy metals, hydrocarbons, oil, rubber, fertilisers, pesticides, detergents and other pollutants build up on your pavers. When it rains, these pollutants end up downstream in rivers, where they damage wildlife habitats. In heavy downpours the speed this might occur can be quite rapid, causing flash flooding, erosion and great levels of damage. With permeable paving, the amount of pollutants entering the water cycle and the amount of water is minimised.
If you’re about to embark on a driveway, patio or any other paved surface and you want to do it the most environmentally sensitive way, talk to us about natural stone paving.
As well as reduce pollutants, permeable pavers:
- Reduce overall irrigation demand
By allowing water to seep into the ground, the direct and surrounding areas will need much less man-produced irrigation. This will save you money and reduce the amount of water used for your everyday irrigation needs.
- Reduce local ambient temperature
Permeable surfaces that are light in colour help to reflect the sun and heat and reduce the local ambient temperature. This improves the health of your surrounding vegetation and improves air quality.
- Control erosion
In areas with loose soil and heavy rain, permeable paving can be used to retain soil and prevent erosion. Serious damage can be done to lawns, gardens and outdoor living spaces if runoff and erosion are not properly addressed and controlled.
- Reduces peak rates of discharge
Permeable paving helps to re-establish a more natural hydrological balance and reduces runoff volume by trapping and releasing precipitation into the ground instead of allowing it to flow into storm drains and out to receiving waters as effluent. This same process also reduces the peak rates of discharge by preventing large, fast pulses of precipitation through the stormwater system.
Why doesn’t every home have permeable paving?
While there are many benefits to permeable paving there are factors that have pushed pause on permeable paving becoming mainstream in Australia. These include:
- Lack of knowledge
Unlike countries such as Germany, England and the United States, Australia doesn’t “need” permeable paving. These countries push hard for permeable paving, making it a requirement in some places. In Australia, it’s down to personal choice and many architects and homeowners simply don’t know enough about the benefits of permeable paving.
The installation of permeable paving requires a large amount of sub-grade work which generally makes it a more expensive solution compared with traditional paving systems. Many people fear that permeable paving comes with higher maintenance costs too, but this is debatable. Oil, grease and fine organic and inorganic matter can build up within the gravel, filling the drainage openings, but regular sweeping will reduce this risk.
Permeable pavers aren’t as strong as traditional or asphalt pavers and if you put consistent pressure on them the pores of the paving can collapse. For this reason, permeable paving isn’t recommended for highways and high traffic roads or for driveways where heavy loading vehicles park. Driveways for standard vehicles are fine.
Permeable paving has many applications, most commonly:
- low-volume pavements
- residential roads and driveways
- parking lots
- low-water bridges
- well linings
- tree surrounds
- walls (including load-bearing walls)
- swimming pool decks
- commercial and industrial environments
- water harvesting
There are also many types of permeable paving, all of which are used for different purposes:
- Porous asphalt is used on highways to remove excess water.
- Single-sized aggregate (commonly known as loose gravel) is seen in very low-speed applications such as driveways or pathways.
- Natural stone is used for its beauty, durability and function. The effect lends itself to an old-world, hand-crafted look that meets modern and environmental standards.
- Plastic grids allow for a 100% porous system and can help reinforce gravel driveways, parking lots, and fire lanes. Plastic grids can also be planted with grass.
- Porous turf can be used for areas with occasional parking, such as stadiums or churches.
- Permeable interlocking concrete pavers are individual units that can be laid out in an interlocking grid pattern, with grass or small stones filling in-between spaces. This type of paving is popular in public areas due to its architectural appeal.
- Permeable clay brick pavers are similar to interlocking pavers but are composed of fired clay.
- Resin-bound paving is a mixture of a clear resin and aggregate, used for areas with pedestrian and vehicular traffic, including walkways, driveways, and parking lots.
- Bound recycled glass porous pavement is a mixture of post-consumer glass with resins and binding agents and is appropriate for both pedestrian and vehicular traffic.
- Wood mulch is highly permeable but will require regular maintenance and topping up from time to time.
For general advice about outdoor paving, contact the expert team at Armstone.
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