Permeable Pavers: Your Complete Guide
Imagine an intense rainstorm. You watch as the rainwater inundates your yard, quickly and creates a giant puddle in front of your house. It’s frustrating, and it seems like every time it rains, your yard turns into a swamp.
But what if there was a way to keep that water from pooling in front of your house, and instead let it seep into the ground?
If so, permeable pavers are for you. They’re a type of paving design that allows water to seep through the cracks and pores in the surface, instead of pooling on top.
This guide will explain everything you need to know about permeable pavers, with information on how they work, the benefits they offer, and some tips on installation.
What are Permeable Pavers?
Permeable pavers are paving stones that allow water to drain through them rather than running off the surface and causing puddles or flooding. They transfer water to the ground below, either through surface pores or gaps between the pavers.
They not only keep water from pooling on your property, but they also help to reduce the amount of runoff that enters storm drains. This is especially important in urban areas, where runoff can carry pollutants and debris into waterways.
How do permeable pavers work?
Although permeable pavers are intended to allow water to pass through, they are not simply pavers placed on top of the soil.
Instead, they are typically a system that includes pavers, multiple layers of crushed stones, geotextile fabric, and, most importantly, a drainage system with overflow protection.
When it rains, water can drain between the gaps in permeable paving slabs or through the special spaces in porous concrete paving. The water is then filtered through a series of crushed stone layers of varying sizes to filter out any debris.
Eventually, the water is drained into an underground drainage system. This can be a gravel trench or a dry well, allowing water to seep back into the soil and groundwater.
Between the soil and crushed stone layers is a geotextile fabric that serves as a filter. It serves two primary functions. It keeps the gravel below from collapsing and keeps silt from rising up between the slabs.
If an overflow is required, it should be built into the system as well. It can be a pipe or a series of pipes that drain excess water from your property and keep damage to your land to a minimum.
We’ll go over the design of such a system in greater detail later in this guide.
Where can permeable pavers be used?
Permeable pavers can be used in a variety of places where runoff from rainwater is an issue. This includes driveways, parking lots, sidewalks, garden areas, and other areas where water drainage is an issue.
However, here are some specific applications for permeable pavers:
Water runoff is a common occurrence in parking lots. When it rains, this can cause puddles and even flooding. This is especially true in parking lots that have dips or are not properly sloped to the road.
Permeable pavers can be used in the parking lot to help prevent water runoff. This will help to keep the water from pooling and will limit the number of contaminants carried into the waterways.
Permeable paving is frequently used in commercial parking lots to prevent runoff. When it rains, water can pass through permeable pavers or porous concrete slabs and into the ground.
This prevents puddles from forming and keeps the area around the parking lot cooler.
Sidewalks are another application for permeable pavers. Permeable pavers installed on sidewalks provide pedestrians with a nice dry and safe walking surface improving pedestrian safety.
Permeable pavers can be used to help retain water in gardens. They serve as a foundation for raised garden beds and can help prevent soil erosion in rainy climates where the ground should not become saturated with water.
Permeable pavers can be used to create driveways. They can not only prevent runoff but also improve road handling in wet or icy conditions.
In comparison to traditional driveways, permeable paving requires less chemical treatment to remove ice and snow.
Airports are critical locations where water puddling can pose a serious safety risk. Airports are using permeable pavers in certain areas to help prevent this.
They can help prevent the formation of puddles and protect the area around the airport in the event of flooding or water pooling on runways.
Service or emergency access lanes
Permeable paving is also used in service or emergency access lanes. These roads provide service and emergency access to buildings, homes, or properties.
As a result, they frequently require a special type of pavement that can withstand high volumes of runoff during rainstorms.
What are the benefits of permeable pavers?
There are a number of benefits to using permeable pavers instead of traditional ones. Here are some of the most notable:
Reduces water runoff and prevent flooding
A permeable paver system is designed to allow water to pass through them and into the ground. As a result, it can help reduce or prevent flooding on your property by limiting surface runoff from roads, sidewalks, parking lots, garden areas, etc.
Using permeable pavers, the water that does end up on your property will be able to easily drain away from your home and into the ground.
Improves stormwater management
Permeable pavers help with stormwater management by slowing and reducing runoff.
The runoff that does occur can be infiltrated into the ground via the paver system. This helps to reduce the amount of stormwater that enters the municipal sewer system.
In some cases, municipalities are even offering financial incentives for installing a permeable paver system.
When there is less stormwater runoff from impervious surfaces, the water that does end up in waterways is cleaner.
This reduces contaminants from entering local rivers and streams which can have a negative impact on the local environment.
Permeable pavers are designed to allow water to pass through them and into the ground.
This means they are able to absorb more water than traditional pavers. Impermeable surfaces like concrete can’t do this, which means it will take longer for the water to dissipate.
Reduces chemical use
Chemicals used for ice and snow removal frequently end up in waterways causing water pollution.
Because a permeable paver system is designed to allow water to pass through them and into the ground, they can reduce or eliminate the need for these chemicals.
Creates a beautiful landscape
One of the other benefits of using permeable pavers is that they can help create a beautiful landscape. Permeable pavers come in a variety of colors, shapes, and sizes which makes them perfect for creating unique designs for your property.
Permeable paving is initially a more expensive option than traditional asphalt or concrete paving.
However, over time they can actually save you money. Since permeable pavers prevent runoff, you will have to spend less money or time after every rainstorm on things like cleaning your driveway or trying to unclog a storm drain.
More importantly, permeable pavers can prevent water from reaching your property’s foundation, saving you money on costly water damage issues and repairs.
What are the Drawbacks of Permeable Pavement?
Although permeable pavers have numerous benefits, they do come with a few drawbacks. These include:
Initial higher cost
Permeable pavements are more expensive to install initially when compared to traditional asphalt or concrete paving methods. However, over time they can save you money by preventing the need for water damage repairs and upkeep costs.
Requires regular maintenance
Permeable pavements require more regular maintenance than traditional asphalt or concrete. This includes cleaning and repairing joints and cracks as they occur.
Requires proper installation
Permeable pavers must be professionally installed by a licensed contractor for them to function properly and last an extended period of time. It’s important that the base material used for the installation is appropriate and that it’s compacted properly to ensure proper drainage.
What are the types of permeable pavers?
There are a number of different types of permeable paving materials. However, the basic principle of all permeable pavements is the same moving water through the pavement and into the ground as quickly as possible.
Most permeable pavers consist of a surface pavement layer, an underlying crushed stone reservoir layer, and a filter layer on the bottom.
The size and breadth of the crushed stone layer are determined by a number of factors, including precipitation, soil, vegetation, and site-specific conditions.
Here are some of the most common types of permeable pavers:
Porous asphalt is a type of bituminous asphalt that has small openings in it that allow water to drain through.
It typically has four layers:
- A layer of asphalt, (2 – 4 inches),
- A filter layer (1 – 2 inches made of half-inch crushed aggregate),
- A 12-inch minimum reservoir layer (made of 1 – 3 inches sized of aggregate),
- A layer of geotextile material.
Porous asphalt has a void space of around 16% compared to 2%-3% in regular asphalt which makes it inherently better at draining water.
The crushed aggregate filter layer removes pollutants and stabilizes the stone reservoir layer during paving. The reservoir bed is made up of open-graded clean-washed aggregate with at least 40% void area.
A nonwoven geotextile put between the reservoir bed and uncompacted subsoil prevents particles from migrating into the stone reservoir and clogging it.
Porous asphalt pavement can endure for up to twenty years before cracking or developing potholes. It is an extremely sturdy product that can withstand rains for many years.
Porous asphalt has been effectively used in parking lots, sidewalks, playgrounds, and high-volume highways carrying big trucks.
Porous asphalt is coarser than conventional asphalt, but it is still smooth enough to meet Americans with Disabilities Act (ADA) regulations, making it an appealing choice to explore during the planning process.
Along with the environmental advantages of porous asphalt, there are also financial advantages to this paving method.
When water runoff from parking lots overwhelms the storm sewer system, some local governments have to spend significant amounts of money on sewage treatment plants.
These impact fees can be reduced because porous asphalt helps lessen demands on storm drains.
Therefore, local governments request developers to install porous asphalt in new construction projects to help offset the cost of these expensive treatment plants.
Porous asphalt will also save you money by eliminating the requirement for a storm-water management system, such as a retention pond.
The land that was previously designated for the retention pond can now be developed and used as a profitable asset that adds value to the property.
Another advantage of porous asphalt paving, it doesn’t require proprietary ingredients.
The aggregate can be found in most quarries, and the asphalt is a commodity product. A qualified contractor should do the asphalt mixture, and it should be ready for paving in about a few hours.
Pervious concrete (Porous concrete, Permeable concrete)
Pervious concrete is a high porosity concrete that is used for concrete flatwork applications. It allows water from precipitation and other sources to pass directly through, reducing runoff and allowing groundwater recharge.
Pervious concrete is made up of cement, coarse aggregate, and water. The aggregate is a mixture of sand, crushed stone, or gravel. The coarse aggregate has void spaces that allow the concrete to breathe and release entrapped air and water vapor.
This reduces the chances of shrinkage cracking and spalling caused by the expansion and contraction of trapped air bubbles.
Pervious concrete has a water water-to-cement ratio is 0.28 to 0.40, and the void content is 15 to 25%. It has a typical strength of 600–1,500 pounds per square inch (4.1–10.3 MPa) but can reach 4,000 psi (28 MPa).
There is no predefined compressive strength test. Acceptance is based on the unit weight of a poured concrete sample as determined by ASTM standard no. C1688.
Pervious concrete is commonly utilized in parking lots, light traffic zones, residential streets, pedestrian walkways, and greenhouses.
Both previous concrete and porous asphalt are one of many low-impact development approaches employed by builders and meet U.S. Environmental Protection Agency (EPA) stormwater requirements by absorbing stormwater and enabling it to sink into the ground.
In fact, the use of pervious concrete is one of the Best Management Practices (BMPs) advocated by the EPA, as well as other recognized agencies for the regional and local management of stormwater runoff.
Pervious concrete can reduce the need for retention ponds, swales, and other stormwater management measures. Since it handles stormwater management on-site, pervious concrete helps builders avoid the additional costs that come with these off-site systems.
Finally. the installation of pervious concrete is also an opportunity to increase the value of your property by increasing its green space.
Interlocking pavers are made out of prefabricated blocks (often brick or concrete) that are placed in such a way that water can move between the blocks and into the soil below.
Generally interlocking pavers create permeability by diverting water to the spaces between the pavers rather than being porous themselves. However, some interlocking pavers have a perforated design, allowing water to penetrate the blocks.
Interlocking pavers come in a variety of colors and shapes, so they can be used to create interesting designs in your landscape. They can be used in both light and heavy-duty applications.
Some of its light-duty applications include walkways, jogging tracks, pool decks, and garden landscapes. While its heavy-duty applications are for driveways, car parks, pedestrian paths, and warehouses.
The difference comes in paver thickness, material, and the way they are laid. For driveways and other high-traffic areas, a more robust paver is recommended that can handle greater loads without crushing.
Most heavy-duty pavers are thicker than 8-10cm while light-duty pavers are around 6cm thick.
Plastic grid pavers
Plastic grid pavers are a type of open-cell unit paver with soil and turf planted in the cells.
They disperse traffic weight and keep the underlying soil from being compressed. They can be filled with gravel or soil and grass, with the former being a preferred choice for higher traffic regions.
The majority of the materials used to make these pavers are recycled plastic. Plastic grid pavers are available as interlocking blocks or rolls.
Plastic grid pavers can be utilized on uneven terrain due to their flexibility, but they do not have the inherent strength of concrete pavers. Drains, detention or retention ponds, or any other connected drainage infrastructure are not required.
They can enhance the aesthetic of property by introducing vegetation where there would otherwise be only pavement.
Plastic grid pavers will benefit from seasonal examinations to spot-check for problems, and those filled with gravel or stone may require aggregate replenishment from time to time.
Grid pavers planted with turf must be cared for in the same way that a lawn is, with regular mowing and watering.
Manufacturers typically provide product maintenance recommendations, although the following is generally true:
- Reseed grass pavers on a regular basis to fill up bare patches.
- Add gravel to gravel pavers on a regular basis.
- Mount rollers to the bottom edge of a snowplow to avoid plastic grid paver edges from catching.
- Avoid excessive runoff from adjacent impervious surfaces since this may result in clogging.
- Avoid aerating turf since it will harm the pavers.
Concrete grass pavers
Concrete grass pavers are a porous concrete and natural stone paving product. They are intended to allow turf and vegetation to grow between the pavers.
They increase rainwater absorption and reduce stormwater runoff not only by allowing water to drain through but also by using plantings. The paving units come in a variety of shapes and sizes that allow for creativity in design.
How to install permeable pavers?
Installing permeable pavers is a fairly easy process. However, it is important to make sure that you are following all local, state, and federal laws when it comes to your paving project.
Plan your project
Before starting any project, it is important to plan everything out carefully. This will help ensure that you are choosing the right type of permeable pavers and that you are using the right materials and installation methods.
It is crucial to consider in advance any vehicular loads, water storage capacity under the pavers, and the grades and slopes of the installation site.
Excavate the area
Once you have planned your project, it is time to start excavating. You need to carefully remove the topsoil from your project site and add it elsewhere on your property, if possible.
After removing the soil, you should compact the subgrade to ensure a solid foundation for your pavers.
Choose a quality geotextile
Geotextile is a fabric that is used to separate and protect the soil from the aggregate and to help with drainage.
It is important to choose a quality geotextile for your project. It should be highly permeable and resistant to tearing and degradation over time.
Before laying the geotextile, you should make sure that the subgrade is smooth and level. The geotextile should then be unrolled over the entire installation area and secured in place.
Lay the base stone
Once the geotextile is in place, the first layer of stone should be laid down. This is what we call the base stone.
The stones in this layer are more often number 2 stones which are about 2 inches in diameter. These stones need to be properly compacted. The base layer can be as deep as the design requires.
Install exfiltration pipe
The exfiltration pipe is the pipe that removes water that reached all the way to the base stone layer.
Install the second layer of stone
The next layer of stone is called the filter or drainage layer. These stones are smaller than those in the base layer, usually a number 57 stone used for this layer. It is a multisized stone ranging in size from one-half inch to an inch and a half.
This layer of stone is typically about 4 inches deep. Once it is in place, it should be compacted with a vibrating plate compactor.
Use edge restraints
Edge restraints are pieces of metal that are used to secure the stone layers. They should be placed along all sides of the permeability area. You can use flexible aluminum or stainless steel edging for your project.
Install the final layer of stone (setting bed)
The final layer of stone is called the setting bed. This is a layer of the smallest stones in your project. They should be typically number 8 stone which is about two inches thick and isn’t compacted before the pavers set on top of it.
Now that preparation of the project site is complete, it’s time to start setting your pavers.
The pavers should be set using string lines to keep the pavers straight and uniform. Always use a full-size paver for the border course. Make sure to measure and mark any paver before making any cuts.
When setting the pavers, start in one corner and work your way out. Use a rubber mallet to gently tap each paver into place. Make sure to use a leveler while installing the paver stones so they are all at the same height and slope.
Top with sand
Once the pavers are in place, you need to add a layer of sand on top. This will help to secure them in place by filling in any gaps between the pavers.
You should use a broom to sweep the sand into all the cracks and crevices.
Finish with compaction
Once the sand is in place, you should finish your project by compacting it. You can do this with a hand tamper or plate compactor.
Make sure to go over the entire installation area several times to achieve the best results.
Side dress job
The edge of the installation needs to be side-dressed to prevent any shifting of the pavers over time and prevent neighboring soil or mulch from entering the installation. Because it will clog the pavers and reduce the permeability.
Now that installation is complete, you should water the area thoroughly. This will help to settle the pavers and activate the bonding between the pavers and the sand.
Are brick pavers permeable?
Brick pavers are not permeable. However, they can be used as part of a permeable paving system by installing them with a planned joint spacing that will allow water to pass through.
In order to achieve this, they should be laid on a bed of crushed stone as it is mentioned in the post.
Do permeable pavers need slope?
Permeable pavers work best on flat or slightly sloped areas. However, if your installation area has a slight slope, this should not be a problem. In order to keep the pavers in place, you can use edging on all sides of your project and compact the soil around them.
If your installation area has a significant slope, you may want to implement additional measures that will help keep the pavers in place and prevent them from slipping downhill.
Can you drive on permeable pavers?
Permeable pavers are designed to be walked or driven on. However, the type of paver and the installation design will determine how much weight they can hold. Always check with the paver manufacturer to get their recommendation.
Can any paver be permeable?
Not all pavers are permeable. In order to be a part of a permeable paving system, the paper must have an open-joint design that will allow water to pass through.
There are many different types of pavers that can be used for this purpose, so it is important to select the right one for your project.
Are permeable pavers worth it?
Permeable pavers are definitely worth it. They have many benefits including reduced runoff, less runoff pollution, and improved aesthetics. Not to mention, they are a great way to help out our environment.
Are permeable pavers easy to install?
Yes! Permeable paving systems are very simple to install however it shouldn’t be a DIY project. Since it requires a multi-layer installation with different preparation and installation requirements, you should hire professionals to complete the job.
Are permeable pavers ADA-compliant?
Permeable pavers are ADA-compliant provided the products used for the installation, and installation techniques follow the Americans with Disabilities Act (ADA) guidelines.
ADA requires permeable pavers to have a minimal transition in between, have a minimal slope, be firm, slip-resistant, and have a smooth surface texture.
There are so many different types of permeable pavers with many different features.
Therefore, we cannot say each and every permeable paver is ADA-compliant from the start. However, you should check with the manufacturer to learn if their product is ADA-compliant.
Can I use permeable pavers in my garden?
Yes! Permeable pavers are great for use in gardens. They help to reduce runoff and improve the aesthetics of your garden while also being functional. The important thing to keep in mind is zoning pavers and planting beds not to block the paver joints.
Are permeable pavers good for roads?
Permeable pavers have been used on roadways in certain parts of the world with great success and without any issues.
However, it is important to use high-quality products and install them properly following industry standards and guidelines. This will help ensure a safe and lasting installation.