- Allow water to filter through the driveway, carpark or path surface into the local soil to increase soil moisture and sustain adjacent vegetation.
- Decrease excess stormwater runoff.
- Stormwater management solution when no underground drainage system exists.
- Avoid downstream drainage system upgrades
- Support maintenance of predevelopment runoff rates and/or more natural hydrological cycle.
- Reduce stormwater ponding on surface of carpark, road or footpath.
- Reduce need for stormwater pits and pipes (and associated cost) while providing improved pedestrian accessibility.
- Provide protection for trees – water infiltration and soil aeration.
Design tipsTIP 1 – Geofabric between bedding course and base layer almost redundant
If ratio of diameter of bedding layer to base course layer aggregate is less than 1:10, then no geofabric is required between the layers.
Why? The materials are close enough in size, ensuring that migration of smaller bedding course material into the voids of base course does not occur.
TIP 2 - To avoid clogging of permeable pavers
Ratio of contributing impervious areas to permeable paving area – no greater than 4:1
TIP 3 – Avoid recycled concrete basecourse
Why? The limestone leaches out of the material and clogs the system.
TIP 4 – Always install an edge restraint or a concrete kerb
TIP 5 – When design is close to a footing or structure
ensure no water enters the subgrade by:
- ensuring a minimum 1% grade of pavement to draw the water away from the structure/wall
- installing an impermeable liner that redirects water away from the footing.
TIP 6 – Use permeable paving to protect significant trees
even if the tree is on an adjacent property.