As commercial development intensifies across Australia’s urban centres, the management of stormwater runoff has become a central focus of both planning and compliance. Expanding roof areas, car parks, and hardstand zones contribute to large volumes of impermeable surface, which can overwhelm local drainage networks, increase flood risk, and degrade water quality.
The solution isn’t just about adding more drains or detention tanks. Increasingly, councils and engineers are turning their attention to infiltration-based solutions that allow rainfall to soak back into the ground where it lands. One of the most effective and adaptable ways to achieve this is through permeable paving systems, such as TRUEGRID®, which integrate seamlessly into commercial sites to manage runoff at the source – from roof to road.
The Growing Challenge of Stormwater on Commercial Sites
Commercial and industrial properties generate some of the highest levels of surface runoff in the built environment. Between roof surfaces, access roads, storage yards, and parking areas, a typical development may be 80–90% impervious. During intense rainfall, this can create peak flows that exceed the capacity of local stormwater systems.
This excess runoff often leads to:
- Localised flooding in car parks and delivery areas.
- Erosion or sediment transport into drainage infrastructure.
- Pollution of downstream waterways from hydrocarbons and heavy metals.
- Increased maintenance and water treatment costs for councils and developers.
Under Water Sensitive Urban Design (WSUD) frameworks and the National Construction Code’s sustainability provisions, developers are now expected to reduce impervious coverage and improve on-site detention. This shift towards decentralised management – capturing and treating water where it falls – has made infiltration pavements an increasingly attractive option.
How Infiltration Pavers Manage Runoff
Unlike traditional sealed pavements, infiltration pavers are designed to mimic natural hydrology. Rainwater passes through the surface and into an engineered stone base below, which acts as both a load-bearing structure and a temporary detention zone. From there, water gradually infiltrates into the subgrade or can be directed to adjacent drainage features such as swales, rain gardens, or infiltration trenches.
The process is simple yet effective:
- Capture: Rainfall and roof runoff enter the permeable surface.
- Detain: The open-graded aggregate base temporarily stores water in its void spaces.
- Filter: As water passes through, suspended solids and hydrocarbons are filtered out.
- Release: Clean water infiltrates slowly into the subgrade, reducing flow volume and peak discharge.
According to TRUEGRID’s technical documentation, a typical base of 19 mm angular stone provides around 40% void space, equating to 0.4 cubic metres of storage for every cubic metre of aggregate. This means even moderate rainfall events can be managed entirely within the pavement structure, eliminating the need for additional surface detention basins in many projects.
TRUEGRID has the highest infiltration rate, often exceeding 20,000mm/hour per hour, followed by permeable pavers which have variable rates depending on material and joint width but Avg 9600 mm/hr per hour* . Permeable concrete can have high infiltration rates initially but can be susceptible to clogging, which can reduce its long-term performance. TRUEGRID, being an open-grid system filled with aggregate or grass, maintains high permeability by preventing clogging.
Infiltration rate comparison
| Feature | Permeable Concrete | Pavers (Permeable Interlocking Concrete Pavers – PICPs) | TRUEGRID |
| Typical infiltration rate | 7000 – 17,000 mm per hour | Variable, but Average is 9600mm/hr | Exceeds 20,000 mm/hour |
| Clogging susceptibility | High, which can reduce performance over time | High, which can reduce performance over time | Low, as the open grid structure prevents clogging |
| Mechanism | Water infiltrates through the porous concrete mix and joints | Water infiltrates through the joints between the pavers | Water infiltrates through the gaps in the open-grid structure, which are filled with aggregate or grass |
| Best for | Areas with moderate rainfall or where a more conventional appearance is desired | Areas where aesthetic variety is important | Areas with very high rainfall, high loads or a need to maximise water infiltration |
*source Comparing Two Methods of Determining Infiltration Rates of Permeable Interlocking Concrete Pavers – by Peter W.B.Nichols, Terry Lucke 1 and Carsten Dierkes
Integrating Roof Runoff into Pavement Systems
Modern infiltration paving systems can also be connected directly to roof drainage. By directing downpipes into the stone sub-base of the permeable car park or driveway, runoff from large roof areas can be managed naturally rather than piped to stormwater drains.
This “roof-to-road” approach creates a unified, on-site infiltration network that:
- Reduces total stormwater volume and flow rate.
- Recharges local groundwater.
- Improves pollutant removal through filtration and biodegradation in the sub-base.
- Helps developments comply with council on-site detention (OSD) and stormwater quality objectives.
TRUEGRID® systems are particularly suited to this application because their modular design allows for flexible integration with site drainage and civil layouts. Roof downpipes can be connected through simple dispersion pits or perforated pipes laid within the aggregate base, distributing inflow evenly and preventing concentration of water at a single point.
Why TRUEGRID® is Effective for Commercial Applications
TRUEGRID® permeable paving systems are engineered from 100% recycled high-density polyethylene (HDPE) and feature a patented S-Flex joint system that provides both strength and flexibility. The system delivers high compressive performance – over 8,000 psi when filled while remaining fully permeable.
This combination makes it ideal for commercial settings such as:
- Retail centre car parks.
- Distribution and logistics yards.
- Mixed-use developments.
- Business parks and industrial driveways.
- Public access and council car parks.
TRUEGRID’s PRO PLUS S-Flex 48 model, for example, has been successfully used in heavy-vehicle applications from crane accessways to warehouse parking and flood-prone sites. The system can be filled with clean, angular gravel for industrial projects or used with turf infill in landscaped public spaces.
Because the grids interlock and can be hand-installed without machinery, construction time is significantly shorter than traditional pavements, reducing disruption for operating businesses.
Environmental and Regulatory Advantages
From a compliance perspective, TRUEGRID® supports WSUD and council stormwater policies in several measurable ways:
- Runoff Reduction: The infiltration base detains rainfall, lowering post-development discharge rates to pre-development levels.
- Water Quality Improvement: Filtration through gravel and soil removes suspended solids, hydrocarbons, and metals before infiltration.
- Heat Island Mitigation: TRUEGRID® promotes air circulation and reduces thermal build-up compared to asphalt or concrete.
- Sustainability: Each installation diverts post-consumer plastic waste from landfill, contributing to circular economy outcomes and GECA-certified environmental compliance.
These benefits make permeable paving one of the most versatile stormwater management tools available for urban development, particularly where space constraints limit the use of traditional detention infrastructure.
Case Study: Integrating Infiltration at Source
At NRMA Turtle Sands Holiday Park in Mon Repos, QLD, the design team faced strict environmental requirements within a protected wetland zone. Conventional asphalt roads were rejected in favour of TRUEGRID® permeable pavers laid directly on the sandy subgrade. The system managed roof and surface runoff naturally through infiltration, maintaining the area’s hydrological balance while providing durable access for vehicles and service trucks.
This project illustrates how a well-engineered permeable surface can achieve both functional performance and regulatory compliance in environmentally sensitive locations.
Designing for Long-Term Performance
When specifying infiltration pavers, proper base preparation is essential. TRUEGRID® recommends:
- A geofabric separator to prevent fine soil migration.
- An open-graded stone base (ASTM No. 57 or equivalent) for optimal infiltration and detention.
- Periodic vacuum sweeping or pressure cleaning to maintain permeability.
With correct design and installation, permeable pavements can deliver a service life exceeding 25–40 years with minimal maintenance – comparable to, or better than, traditional pavements.
Conclusion: Building Smarter, Cleaner Commercial Sites
The integration of infiltration pavers represents a fundamental shift in how commercial developments manage stormwater. By capturing runoff directly at the surface and returning it to the soil, developers can reduce infrastructure costs, meet council WSUD requirements, and create cooler, cleaner, and more sustainable sites.
TRUEGRID® permeable paving systems provide a proven framework for this new generation of water-smart design. From roof to road, they connect durability with environmental performance – helping Australian businesses and councils build infrastructure that works with nature, not against it.
