Permeable Pavers vs. Porous Asphalt
Which is the Best Choice?
Types of Paving Systems
When deciding which type of paving system to use on a driveway, parking lot, commercial property, or any kind of paved surface for that matter, it is important to understand the differences in new paving technology. For years, contractors and homeowners alike had few choices. Impermeable concrete and asphalt was the general consensus, and a matter of choice or selection in this field was quite rare.
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Paving Problems with Asphalt and Concrete
Traditional paving materials such as asphalt and concrete causes problems with the environment. In urban areas that are significantly paved, asphalt and concrete do not allow for natural water drainage, and this puts unnecessary stress on sewer and draining systems. This also creates broader ecological problems. Storm water is not able to seep naturally back into the soil. It runs over and off of traditional asphalt and concrete, over-flowing city septic systems and damaging nearby watershed ecosystems. Plus, debris, even on a microscopic level, gets carried into nearby water sources as opposed to just leeching naturally into the soil. Through a natural leeching process, those negative materials could be broken down and nullified. In a runoff scenario as a direct result of traditional paving systems, such materials act as pollutants.
Runoff Water Poses Additional Problems
As touched on lightly above, water runoff from impermeable asphalt and concrete picks up oil, fertilizer, gasoline, cleaners, de-icing salts, and other chemicals and sheds such pollutants into local water systems, lakes, rivers, etc. Our country has made strides just within the last decade to change all of that.
Different Forms of Eco Paving
Enter in the concept or permeable, pervious, and porous paving material as a form of “eco paving” if you will. Do these terms all sound the same? Yes. Are they the same? No. Just with any other field of construction in both commercial and residential industries, it is important to know the differences between these terms.
Paving Materials; “Porous,” “Pervious,” and “Permeable” Defined
It goes without saying that it is easy to get confused when similar terms like “porous,” “pervious,” and “permeable” start getting thrown around. Let’s look at these technologies and compare them:
Porous asphalt is really only a slight modification of traditional asphalt. This type of asphalt is even installed in the same way as traditional asphalt. However, the key difference here is that small aggregate materials that would normally be included in traditional asphalt are omitted in porous asphalt. This leaves larger aggregate mixtures in the asphalt which allows for open voids and pockets that create true porosity. As a result, water can flow through the asphalt as opposed to resting on top of the asphalt.
Pervious concrete is very similar to porous asphalt. Pervious concrete is thought to be more affordable slightly than permeable pavers discussed below, yet is more expensive than porous asphalt discussed above. Pervious materials are more susceptible to freeze-thaw damage than porous materials, yet can retain more water than porous asphalt. Infiltration rates of water leeching is hundreds of inches per hour initially for pervious concrete, but over time this can become as low as five inches per hour because of clogging. Pervious concrete is quite like traditional concrete, yet it contains little to no sand, which ultimately results in a pervious, open-cell structure that water easily passes through.
Permeable pavers for driveways are a very specific technology. Permeable pavers are arranged in a system of networked paving material (which, by the way, allows for exceptional customization with near-infinite options for a unique, permeable driveway or parking lot). Permeable block paving uses a system of tough, concrete pavers laid out in whatever pattern is requested by the client. Cracks are left between each paver, allowing for rapid drainage of water between the pavers. From there, water seeps into a cleansing layer of gravel. The gravel under-layers, (there are usually two or three separate layers of different sizes of gravel or aggregate installed below the pavers), acts as a natural filter, cleansing the water of pollutants and other, unnatural substances that would otherwise shed into nearby surface waters.
Permeable Pavers; the Best Choice for Contractors and Homeowners
Permeable paving systems for contractors and homeowners allow for the most efficient application of green pavement. An article in “How Stuff Works” discusses further how “eco-paving” was applied to utilize permeable block paving and asphalt paving in Chicago, Illinois. One quote from the article noted that:
“In 2007, the city implemented its Green Alley Initiative. Alleys were (and continue to be) retrofitted with permeable pavement, which will lessen flooding and send water back into the ground in an environmentally safe manner. Designed to reflect heat rather than absorb it, the permeable pavement can also lower temperatures in the immediate area.” 1
Permeable Pavers are the most Cost-Effective
Moving forward, one study done by the Wisconsin Department of Transportation delves into the key differences between porous asphalt, pervious concrete, and permeable pavers as compared to each other and as compared to traditional methods. The following is a cited quote from their report on the matter, showcasing permeable pavers as being the most cost-effective choice when compared to traditional methods:
“Maintenance costs are $400 to $500 per year for vacuum sweeping a half-acre parking lot three to four times annually. One analysis suggests that the 25-year life-cycle cost of a 40,000-square-foot parking lot constructed with one brand of block paver (including installation, biannual vacuum sweeping and other maintenance) is $190,200 compared to $275,875 for impervious asphalt.” 2
And…they Last “Forever”
Perhaps the greatest benefit to permeable pavers over pervious concrete and porous asphalt is that permeable paving systems essentially last forever. All three systems require maintenance, but because of the inherent design of using pavers which filter water around each, individual paver, these systems can be cleaned and the sand between each paver vacuumed out and replaced rather easily. With porous asphalt and pervious concrete a similar method can be used, but the fact of the matter is that eventually these systems will become too clogged even for maintenance to handle and they will then be akin to impervious and nonporous systems. Permeable pavers, correctly installed by PICP-certified contractors offer the best value for the investment and for the longevity of the completed project by far.
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Don't Forget the FAQ! - Questions We Get from Customers About Permeable Pavers
Still have questions about permeable pavers? Wondering if such a system is right for you? 21St-century permeable pavers are a relatively new technology, so homeowners and business owners often have questions about this miracle of paving tech. We want our friends and neighbors in Nashville to think of our team when they ask, “Who is the best landscaper in Nashville?” or “Who is the best hardscaping contractor in Nashville?” To help earn that position, we've compiled a brief FAQ below. If you still have questions at the end of it, don't hesitate to call our office direct at (615) 422-5263.
- Where can I use permeable pavers?
- You can use them just about anywhere. Our customers have permeable pavers installed on their outdoor patios, walking paths, garden paths, sidewalks, entryways, parking lots, outdoor events spaces, driveways, decks, etc.
- Which companies supply the pavers?
- Our design and installation crews work with several paver manufacturers, each of which brings their own special offering to the table. We work with Belgard Hardscapes, Pavedrain, Red River Hardscapes, Unilock, and the Pavestone Company.
- How long do pavers last?
- Essentially indefinitely. Permeable paver systems take their design inspiration from ancient European paving methods, like the Roman roads of old which are still around today.
- Will I ever have to get my pavers refinished?
- No. While permeable pavers require some maintenance once every five years or so (simply by replacing the fine-grit stone between the pavers) the pavers themselves shouldn't require refinishing.
- How long does a paver installation job take to complete?
- Most permeable paver jobs can be completed in about one to two weeks.