Permeable paving is becoming a more and more common type of water-sensitive urban design (WSUD) asset used to meet infiltration and pollution reduction targets. It is one of many types of WSUD asset types, designed to better manage stormwater, reduce flooding risks, and improve water quality.

By allowing rainwater to filter through the surface into the ground, permeable paving supports groundwater recharge and reduces pressure on stormwater systems. Since 30% or more of a city is impervious, permeable paving is critical in reducing volumes and pollution.

This blog post explores what permeable paving is, the types available, how to maintain it effectively, and a real-world example from Melbourne, including costs.

Types of Permeable Paving

There are several types of permeable paving systems, each with its unique structure and benefits:

Porous asphalt – Looks similar to traditional asphalt but has air voids to allow water to pass through.
Permeable concrete – A cement-based material with reduced fines, creating larger void spaces.
Permeable recycled aggregate – Replaces aggregate with a recycled tyre or plastic product, also with reduced fines, creating larger void spaces and supporting a more circular economy approach to city design.
Interlocking permeable pavers – Concrete or clay units with gaps filled with small stones to aid infiltration.
Plastic grid systems – Lightweight plastic grids filled with gravel or grass, ideal for overflow parking and access roads.

Maintenance example

Over time, permeable surfaces can become clogged with sediment, reducing infiltration rates. Regular maintenance is essential to keep them performing effectively. Cleaning typically involves the use of a regenerative air vacuum or high-pressure water cleaning combined with suction to remove trapped sediments from the surface and the voids beneath. This process restores the permeability and prevents water pooling or runoff issues.

In Melbourne, our WSUD maintenance team at Wave Maintenance recently cleaned three different streets with permeable asphalt, using a combination of methods. The cleaning process took three days (so approx. one day per street) and restored infiltration rates significantly (research shows it can increase by a factor of 100). The cost was approximately $1 to $5 per square metre per year, depending on the degree of clogging, sediment load, and accessibility. Accessibility is the greatest issue in cleaning permeable paving (due to residents parking on or near the surface you want to clean), and the ongoing need for water. We used approximately 2,000 to 3,000 litres of water for this cleaning process of three streets, which isn’t much, but presents logistical challenges.

For large municipal projects, economies of scale can lower the per-square-metre rate, but for smaller private projects, the rate may be slightly higher due to setup and mobilisation costs.

Conclusion

Permeable paving is a smart, sustainable choice for urban environments, but it requires ongoing care to remain effective. Understanding the types available, maintaining them, and budgeting for maintenance ensures they deliver their full environmental and functional benefits.

Cleaning permeable paving more regularly would be easier, and probably cheaper, than avoiding this maintenance, and would also allow the surface to infiltrate more water. Access is the main impediment for more efficient maintenance, particularly in residential streets.