Permeable pavers add a lot in the way of runoff management for landscapes and hardscape designs. They allow stormwater runoff to filter through surface voids to an underlying stone reservoir where it’s temporarily stored and/or infiltrated. In addition to reducing the runoff from the rain that falls on them, permeable pavements can help filter out pollutants that contribute to water pollution. Depending on the design, paving material, soil type and rainfall, permeable paving can infiltrate as much as 70-80% of annual rainfall.
Permeable paving materials are not specifically a singular item, but rather a group of materials and landscaping techniques that use holes—minute in size, or larger in some cases—to manage water runoff. Permeable paving techniques include porous asphalt, pervious concrete, paving stones and manufactured “grass pavers” made of concrete or plastic. Paving stones are impermeable blocks made of brick, stone or concrete set on a prepared sand base. The joints between the blocks are filled with sand or stone dust to allow water to percolate downward. Grass pavers are a type of open-cell unit paver in which the cells are filled with soil and planted with turf. The pavers, made of concrete or synthetic, distribute the weight of traffic and prevent compression of the underlying soil.
Permeable pavers are appropriate for pedestrian-only areas and for very low-volume, low-speed areas. This is because permeable paving has a lower load-bearing capacity than conventional pavement.