What Is Permeable Paving and How Does It Drain?
As an Amazon Associate we earn from qualifying purchases.
What is permeable paving and how does it drain? It is a hard surface with open spaces that lets stormwater soak through instead of running off. The surface may be poured concrete or asphalt with the fine material removed, or it may be a set of paving stones laid with gaps between them. Water passes through the surface, moves into a drainage layer of rock below, and then either soaks into the soil or is carried away by a pipe. This page explains the parts of that process using two municipal sources and notes where those sources stop.
Quick answer
- Permeable pavement lets stormwater infiltrate through its surface into drainage layers and the soil below.
- Water either replenishes groundwater or is removed by a sub-drain that connects to the stormwater system.
- There are two main types: permeable concrete or asphalt poured on site, and permeable paving stones set with gaps.
- The sources describe the drainage path clearly but give no lifespan or maintenance schedule.
What makes a surface permeable
The City of Calgary describes permeable pavement as “a type of hard surface with large spaces that allows stormwater runoff to infiltrate into drainage layers and the underlying soils below.” The same page gives another name for it, pervious or porous pavement, and notes that it can be made from porous concrete or asphalt. The key idea is open space. A solid surface sheds water and sends it along the gutter. A surface with open voids lets water go through it.
The Calgary page gives the mechanism for the poured type. The page says the difference from solid concrete is that “fine material like sand is removed from the mix to create larger void spaces in the final pavement for water to flow through and into the drainage layers and soil below.” The surface looks much like solid concrete or asphalt, but the material has open voids.
For the stone type, the Calgary page describes permeable pavers as “solid individual units typically made of pre-cast concrete, brick, stone or cobbles.” The paving stones are set with gaps between them. Those gaps let water flow between the units and down into the layers below. The solid units themselves do not need to be porous. The openings are between the stones.
How the water moves down
Water that passes through the surface enters a drainage layer. The Calgary page says this water “either replenishes ground water sources or is removed by a sub-drain placed in the drainage layer that connects to the existing stormwater system.” So the drainage layer has two possible outcomes. In a place where the ground drains well, water can soak down to replenish groundwater. Where it does not, a sub-drain carries the water out to the stormwater system.
Coventry City Council gives a simpler description of the same movement: “Permeable paving works by permeable surfaces allowing water to soak through the surface into the ground below.” The council also explains the problem that permeable paving is meant to solve. It says that “Paving over front gardens adds to the problem as additional water enters the drainage system, rather than filtering away through the soil.” Hard, sealed front gardens send rain into the drains. Permeable surfaces keep more of it on the property.
The Calgary page also gives the reason councils care. Its list of benefits includes allowing groundwater levels to be replenished, reducing peak runoff periods that can minimize local flooding, and reducing the total volume of stormwater runoff from a catchment area. It adds that filtering pollutants happens “through the rock drainage layers and the subsoils below.” The page refers to research showing that permeable pavement can remove total suspended solids, heavy metals, oil and grease. Those are the page’s own claims about research, and this page does not test them.
Types you will see
The Calgary page names two main types. The first is permeable concrete and asphalt, poured on site. The second is permeable paving stones. Coventry’s guidance on driveways lists a wider range of options, and it is worth reading both sources together.
Coventry describes loose gravel as the simplest option: “Loose gravel is the simplest type of permeable paving to construct, and it is cost-effective.” Its description says the driveway sub-base is covered in a layer of gravel or shingle, with a strip of block paving or asphalt at the entrance to limit loss of the gravel. Coventry also describes paved tracks that align with car wheel tracks, with permeable material between them, and hard porous surfaces that include porous concrete blocks and porous clay block paving. For those, Coventry says the “material has gaps between the blocks which allows the water to soak away” and that it “has a permeable sub-base.”
Coventry also lists two options that are not paving at all. One directs water from an impermeable surface to a bordering rain garden or soakaway. The other uses water butts or underground rainwater tanks to reduce runoff. Coventry describes a rain garden as “a depression in the garden to collect and store rainwater before allowing it to soak away into the ground or flow to the drains.” These do not replace a paved surface, but they can work alongside one.
How we chose
We chose these two sources because both are municipal government pages, both are about stormwater and drainage, and both were opened and read during this check. We did not use any retailer, product listing or manufacturer page. We kept only statements that describe how the surface and drainage layers work, and we quoted the fetched text directly.
What we could not verify
The sources describe how permeable paving drains, but they do not say how well it works in a particular soil, slope or rainfall pattern. Neither gives a design depth for the drainage layer, a permeability rate, or a figure for how much runoff a given area will reduce. The Calgary page links to a development approvals checklist, but the checklist was not opened for this page, so it is not used here.
What the sources do not say
The sources do not say how long permeable paving lasts, how often it needs cleaning, or what happens when the voids fill with sediment over time. They do not give costs or compare permeable paving with standard pavement on price. They also do not say how to install a sub-drain or how to size one. For any of these questions, a local building or stormwater office is the place to check.
Frequently asked questions
Is permeable paving the same as ordinary paving?
No. Ordinary paving is solid and sheds water to the edges. The Calgary page describes permeable pavement as a hard surface with large spaces that lets stormwater infiltrate into the drainage layers and soil below.
Where does the water go after it passes through?
According to the Calgary page, it either replenishes groundwater or is removed by a sub-drain in the drainage layer that connects to the stormwater system. Which of the two happens depends on the site, and the page does not say how to tell which applies to a given yard.
Can permeable paving be used on a driveway?
Coventry’s guidance describes permeable driveways as one of three solutions. The options it lists are directing water to a rain garden or soakaway, using permeable block paving, porous asphalt or porous concrete, and permeable paving itself. The guidance does not state a load limit.
Does permeable paving clean the water?
The Calgary page says filtering pollutants happens through the rock drainage layers and the subsoils below, and it refers to research on the removal of several pollutants. This page reports that claim as the source makes it. It does not verify the research.
Is gravel a form of permeable paving?
Coventry describes loose gravel as a type of permeable paving and says it is the simplest and most cost-effective to construct. It also notes that a strip of block paving or asphalt at the entrance helps keep the gravel from spreading.
For related water topics, see how to assess soil drainage and how to make a rain garden in your backyard.
Sources
- Permeable pavement. City of Calgary Water. https://www-prd.calgary.ca/water/stormwater/permeable-pavement.html (opened 2026-10-27)
- Permeable paving, print version. Coventry City Council. https://www.coventry.gov.uk/water-management-flooding/permeable-paving/print (opened 2026-10-27)
