We’re on the phone with the sales director of an Australian sustainable paving manufacturer, and she’s telling us that there is nothing specifically about permeable pavers in the National Construction Code (NCC) or Australian Standards.
This piece of information only highlights what Tori Newton from Stoneset mentioned earlier in our conversation – that despite the advances in permeable paving products, there remains a lack of awareness within the Australian AEC industry about what is available in a relatively small market.
“[Permeable pavers] have been well-designed and well-tested for 20 years,” Newton explains, “but building confidence in this paving method is taking a bit of time.”
Understandable, we think, considering the lack of set testing and the fact that permeable paving is not a legal requirement in the Building Code of Australia (BCA). Add to this the diversity of permeable paving products on offer, which range from fully permeable concrete and ceramic pavers, to solid paver products that rely on structural gaps for infiltration and various resin based products, and the task of developing a national standard becomes even more complicated.
SO WHAT? WE DON’T NEED PERMEABLE PAVERS
Unlike countries such as Germany, the UK and the United States, where “confidence in utilising this sort of design is very high” and therefore “specified in much vaster areas”, the use of permeable pavers is not as widespread in Australia, even though pavers themselves make up a large part of our landscape.
According to John Wells from Hydrocon, the reasons stopping architects and designers from specifying permeable pavers include a lack of awareness of the benefits of permeable paving; a lack of concern by authorities over the rapid increase of impervious surfaces; and an aversion to risk and liability issues in the specification of unfamiliar and new systems. He compares the existing industry mindset in Australia to the US, where the National Ready Mix Concrete Association highly encourages the use of poured in situ ‘pervious paving’, and the UK, where permeable pavers are part of the Sustainable Drainage Systems (SuDS) toolbox heavily promoted by the Precast Concrete Paving & Kerb Association.
“Germany is arguably the country most advanced in its adoption and support for permeable pavers (PP) through certification of product; state and local regulations favouring the use of PP for stormwater management; and incentives for property owners to install PP as a means of reducing off site discharge and improving ground water quality,” Wells adds.
Aquaroc by Belgard. Photo courtesy of Belgard Hardscapes
Referring to systems that allow air and liquids to pass through, the use of permeable pavers dates back to 1800s Europe, with the technology growing in popularity after World War II because of cement shortages. However, the Green Building Alliance notes that specific implementation of porous pavements only really occurred in the late 1960s to “promote percolation, reduce storm sewer loads, reduce floods, raise water tables and replenish aquifiers”. It is these quoted phrases that set permeable pavers a part from their standard concrete or asphalt counterparts.
As concrete, brick, tile, steel and other hard surfaces take over soil and dirt in our cities and suburbs, the chances of flooding, polluted surface runoff and erosion occurring increase. The traditional way to mitigate these problems is by ensuring the design of good surfacewater disposal and drainage systems, as is set out in the NCC – Damp and Weatherproofing section (Part F1). But permeable pavers also get the job done.
By absorbing and retaining rainfall and stormwater runoff, permeable pavers allow water to be infiltrated into the ground or directed to the nearest storm drain. Boral’s Hydrapave Permeable Paving solution, for instance, directs infiltrated water through small channels formed on the ends and sides of its concrete pavers, passing into a prepared sub-base.
“The water is then detained, filter treated and dispersed, discharged or redirected for re-use,” Mark Dell, National Sales and Marketing Manager of Boral Roofing and Masonry, says. Compare this to hard surface paving, which instead speeds up the flow of water, often carrying with it pollutants like debris, to creeks and streams when flash flooding takes place.
Right: Boral’s Hydrapave system allows water to infiltrate through 4mm deep vertical channels at each end of the 80mm thick concrete pavers, and into a prepared 50mm bedding course where pollutants are naturally filter treated.
The water is then dispersed into the sub base through a series of graded gravel layers, penetrating to the trees’ root systems through the pavement and via the specially prepared ‘structural soils’ beneath, to a final layer comprising a 50/50 mix of topsoil and 50mm diameter multi-faceted basaltic rock – used as a growing medium for new trees. Any excess water is drained away through an agricultural drain into the stormwater system by means of an agricultural drainage system.
Another similar paving system that slows the effects of local flooding, lowers the chance of erosion and acts as a filtration system, is Belgard’s Permeable interlocking concrete pavers (PICP). Installed with layers of stone or variously sized aggregate underneath, Belgard’s PICP mimics the way natural land absorbs water, effectively doubling up as a water management system.
Left: In the US, permeable pavers have spilled over from the commercial market into residential areas. Belgard’s Subterra PICPs, for example, offer the natural look homeowners desire while reducing flooding and improving local waterways.
These systems furthermore help reduce water demands, for example when installed over grassed areas. This means porous pavers can assist the growth and improve the health of mature trees near to the paved areas – important generally for the community, and for architects who have to respect preservation orders.
“Traditional residential and commercial paving systems do not allow for water to infiltrate the paved surface and therefore can shut off necessary water supply to tree roots,” Dell explains.
“When used in a suitable application, the benefits of permeable pavers are numerous, including channeling roof water run off to the sub-base to maximise water catchment,” he adds.
Take the largest permeable pavers project in North America as an example. After residents in a few neighbourhoods complained about heavy rains sending runoff and raw sewage into their homes and backyards, the city of Atlanta spent almost US$15.8 million replacing six miles of asphalt streets with permeable pavers. The project is not only set to resolve the unwanted surface runoff problem; it is also expected to provide up to 7.1 million gallons of capacity relief for areas impacted by flooding.
“There is a lot of runoff from urbanisation over time and water runs off quicker off of paved services than green surfaces. So basically, this provides a green solution to our stormwater runoff,” Todd Hill, Director of Environmental Management for Atlanta’s Department of Watershed Management, told Atlanta’s NPR Station in 2015.
Permeable paving systems also work to counter urban heat island effects. Through a process called the wicking effect, water that is soaked into the ground via these porous pavers evaporates during subsequent periods of hot or fine weather, which cools the air and lowers surface and ambient temperatures.
Despite the advantages of specifying permeable pavers and the fact that it offers best practice in terms of sustainability, there is one catch:
“The installation of permeable paving requires a large amount of sub-grade work,” Dell says, “which generally makes it a more expensive solution than traditional paving systems in terms of installed system cost.”
Tori Newton agrees, noting that Stoneset proclaims to be “the best” sustainable paving option, not the cheapest.
This presumed high cost of installing permeable pavers, combined with no or minimal regulations and a natural aversion to trying something new, is manifested in the obvious lack of local projects that employ porous pavers. For instance, when we reached out to a few Sydney and Melbourne practices inquiring about their notable public projects, somewhat certain that permeable pavers would have been used (however minimal), we received responses saying the contrary was true.
It probably doesn’t help that the belief that permeable pavers have higher maintenance requirements still exists. Hydrocon’s John Wells says that early cases of permeable pavers relying on gaps for infiltration clogging have led to some inertia in the use of the product. Meanwhile, a 2009 paper by Professors from the Centre for Water Management and Reuse at the University of South Australia; School of Civil and Environmental Engineering at UNSW, and a researcher at the CMAA acknowledges that PICPs are generally perceived to retain up to 90 percent of solids suspended in the water infiltrating pavements. The paper specifically points to studies that confirm the infiltration capacity of test pavements “decreases as the amount of oil, grease and fine organic and inorganic matter accumulates within the gravel, filling the drainage openings”.
However, it goes on to note that these problems are economically and readily resolved by using conventional street sweeping equipment. It furthermore states that since PICP construction in Australia began in earnest about 10 years ago, most pavements using such systems have performed well over time without being subject to any systematic maintenance.
CAN’T STOP, WON’T STOP
In spite of the multiple studies proving the benefits and low maintenance requirements of permeable pavers, any claims of the goodness of existing products are somewhat delegitimised by the lack of national or state legislation, national standards of planning policies. Yet, the slow uptake of porous paving does not mean no uptake at all, with practices such as Place Design Group and the Brisbane City Council specifying a resin and stone product on all new street tree planting in the Brunswick Street Mall project. Nor has the lag slowed down manufacturers’ drive to innovate and develop new products, such as Stoneset’s Sudstech Porous Paving solution.
To be released later this year, Sudstech is a high performance resin bound porous paving solution that drains water effectively through its layers, thereby eradicating standing water. Fully compliant with the requirements of Sustainable urban Drainage Systems (SuDS) to better manage water runoff in urban areas, the product is BREEAM accredited and CRE tested; impervious to tree root intrusion and cracking, and comes with a ten year porosity guarantee that combats flash flooding. It is also extremely low maintenance, and is expected to remain porous throughout its life.
The primary difference between Sudstech and earlier incarnations of the product is that it is produced to be even more environmentally friendly; with a unique system of resin bound aggregate over recycled car tyres.
Stoneset Sudstech Porus Paving Solution
Another newly introduced product in Australia is Hydrocera, a permeable ceramic paving product by Hydrocon that has already been used successfully in Japan and Hong Kong. Coming in 10 colours and a range of sizes, Hydrocera boasts a superior finish and is ideal for CBD, suburban shopping centre, apartment and public infrastructure developments. The product’s first specification and installation project is at Fitzgibbon Chase, an outer suburb of Brisbane.
2300sqm of Hyrocera pavers in 19F Brown were used for the transformation of the former Kai Tak International Airport runway to the Kai Tak Runway Park in East Kowloon, Hong Kong. The Kai Tak airport runway was previously known as ‘Runway One Three/Runway Three One’ in the aviation industry, and the numbers ‘13’ and ‘31’ have reappeared on the permeable paved area of the park. Hydrocera is marketed as Ecosystem Tile in Japan and China.
It is also important to acknowledge that local government authorities are starting to require permeable paving as a condition of Development Approvals (DA), especially where the proposed impermeable footprint exceeds the specified permeable/impermeable ratio. This means that even while there are no such requirements for porous pavements in water, environment or building regulations, some property owners will need to install permeable driveways or footpaths to meet the soft to hard landscape ratio. Moreover, an increasing number of councils – and the Australian government in general – are concerned about tree protection, which has an indirect impact on the use of permeable pavements.
Although permeable pavers are not a legal requirement in the BCA, there are some guides that dictate best practice for such products. These include AS 4455 – Masonry Units and Segmental Pavers and the Concrete Association of Australia (CMAA) guidelines if you are specifying concrete permeable pavers.
The CMAA further provides ‘Permpave’ and ‘Locpave’ software to enable for hydrology and hydraulic design of the pavement, sub-grade, base, bedding layer and paver thickness. This includes data from the following documents:
Specification guide – Concrete segmental pavements T44
Design Guide – Concrete segmental pavements T45
Detailing guide – Concrete segmental pavements T46
Breaking load and slip resistance are other important benchmarks to watch out for when choosing your next permeable paving product.
AquaRoc by Belgard Hardscapes
Hydrapave by Boral