This discovery started with a simple, seemingly innocent question, “why not use a permeable paver to deal with poor drainage?” Months later, following many unfruitful searches, I can pretty confidently say the answer is simple: there once was a permeable paver, also called drainable paver on the market, but it no longer exists.
I got the question from our client, a school district project manager who had a problem with standing storm water. An existing area with conventional pavers turned into a pond during big rains. Sloping the pavers to drain the water away wasn’t an option. The surrounding area was virtually flat so we couldn’t direct the water away. Letting the water soak into the ground with a permeable paver system made the most sense.
Now to be fair, there are pervious paving systems on the market. Thanks to technological advances and an increasing demand for green building products, systems that use spacers to channel water between otherwise solid paving units are available. PaveDrain actually vaults its solid paver units to hold water after it flows down between the units.
Poured products offer direct alternatives to impervious hardscape materials like concrete and asphalt. RainCrete is one of these products that we have specified in the past when faced with limits on impervious cover.
We actually have a 6 x 6 sample of permeable concrete in the office. It looks just like any outdoor paver, but water flows right through it! So why not replace all the old, non-permeable patio tiles with a new system of pervious tiles? It’s a small area, so even if the pavers came with a premium price, the school district would have a good solution.
The not so obvious problem is that currently, pervious systems like RainCrete only come in large batches; they don’t make paver tiles. Any Lowe’s or Home Depot will have stacks of concrete pavers, put every one is impervious. I guess it’s so obvious now, but at some point, the concrete industry had to create pavers to compete with stone or brick pavers. But sadly, the impervious pavers aren’t there.
So we used a system of solid pavers with spacers between at the school. We did consider pouring in the permeable material, but the small application made RainCrete too costly.
I still think the best product would have been a paver unit made of permeable material. Which is frustrating since we have a sample in the office! I even joked with one supplier. If he couldn’t sell me the permeable tile, couldn’t he just give us 300 samples?
As I prepared to publish this blog, I did find new information. I found a video from 2010 promoting a new product called Xeripave. I found the company that manufactured it and spoke with Rick whose company used to manufacture it.
“After nine years or so of trying to make a go of it, we finally gave up on the product,” Rick told me. The polymers they used to bind the aggregates were costly, so the product’s price point limited its appeal. And like many new products, some things still needed work. Rick noted that in areas with lots of debris the pavers would fill with silt and limit the water flow. I still think there’s a need for a product like Xeripave. If someone decides to produce it, please let me know!
For more tips from Heimsath Architects' work with sustainable design, here's a great resource: