All year, I’ve been battling the small forest sprouting between the pavers on our patio. The thick stone slabs sit too close together for me to properly dig out the deep taproots of dandelions and other weeds. 

A proper foundation — including a geotextile barrier — would have prevented the issue. But that ship had sailed long before my partner Doug and I bought our West Seattle cottage in mid-2019. I was stuck fighting a rearguard action in what felt like an unwinnable war.

Having been raised by hippies, I am always reluctant to deploy pesticides, even organic ones — especially when they might wash onto our newly transplanted moss lawn. So when a friend mentioned polymeric sand, a paver-joint filler, I researched just enough to make a bad decision.

An early misstep

Polymeric sand blends fine grains of sand with bonding agents. Spritzed with water, it hardens into a concrete-like substance, discouraging weeds and also ants. Not even the common stumbling points dissuaded me. I felt confident in my ability to sweep away the excess polymeric sand, so it wouldn’t crust on the stone. And Seattle’s driest summer on record made it easy to find the required 48-hour period with no precipitation.

I blazed forth and knocked the project out. The polymeric sand firmed up to a Play-Doh consistency, then hardened to feel like grainy cement. (The directions say not to touch it. But, of course, I couldn’t resist poking at this weird science project in my yard.) 

My patio no longer resembled a Chia Pet, and I took a victory lap.

Advertising
The author’s first attempt at removing rust stains from her patio involved hydrogen peroxide, a nylon brush and lots of scrubbing. (Courtesy of Aamanda Castleman)
Paved in rust: The author’s great stain-removal odyssey

Then I started learning more about how this grout can crack during extreme freeze-and-thaw cycles, and how it only lasts a few years in damp environments. D’oh! Worse, it involves some unpleasant chemicals and can knit paving stones into a solid mass. Hard surfaces like this block rain from seeping into the soil, filtering out pollutants and replenishing the water table, while runoff can create erosion issues or even flooding. This is why cities restrict the ratio of impermeable surfaces (like buildings and old-school concrete and asphalt) to permeable ones (plants, turf, garden beds and permeable pavers) on each lot.

Would our 60-square-foot patio cause Highland Park Hill to sluff into the Duwamish River? Probably not. At most, it might channel some extra water towards our Little Free Library’s base, increasing its slight wobble. But I sure felt guilty about my impulsive choice being less than ideal for the environment. So, I turned to experts to discover alternatives for next time.

Simple solutions

Polymeric sand shuts down one of paving stones’ greatest selling points, according to Joshua Erlich, System Pavers’ vice president of operations for Washington state. “You’re basically creating a slab,” he says. “You’re not going to be able to pull the pavers up and set them back down easily.” This becomes problematic if you need to replace a cracked paver or access a buried pipe.

Properly installed pavers should include aggregate, geotextile barriers and sharp bedding sand. The grains’ angles lock together into a compact surface, preventing seeds from rooting and pushing up through cracks. Then only “little surface weeds” can gain purchase, Erlich explains.

“Just make sure to clean off any organics that fall on your pavers, like leaves and pine cones,” he says. Not only do these yard droppings break down into plant-nurturing soil, but they can also stain stone and concrete.

A lot of people in western Washington steer into the skid by intentionally growing moss between their paving joints, which creates a lush, natural look. However, “you can get that easily by not doing anything!” Erlich notes.

Advertising

For his own home, Erlich chose crisp geometric pavers with tight beveled edges, and used sand to discourage weed growth. Modern-style pavers offer less purchase for weeds than old-world looks involving tumbled rock or cobblestones, he says.

Going with the flow

I learned from paving pros that new jointing compounds avoid some of the worrisome aspects of polymeric sand. Daniel Evans, Seattle’s residential representative for Belgard Hardscapes, suggests using Nocostorm, a product made by Techniseal, which shares a parent company with Belgard. It can be applied in wet conditions and stands up to drizzly climates. Best of all, it’s permeable.

The industry has begun to manufacture more pavers with wide spacer bars, Evans says, which help rainwater reach the soil. “A really good system can allow upwards of 400 inches of water to free-flow through in an hour,” he says.

Evans anticipates that homeowners in the Pacific Northwest will soon develop a deeper passion for pavers.

“You see them all over the place back east, and they’ve slowly made their way across the country to California and then up to us,” he says. This region is a leader in “really wanting and caring about sustainability, not just what a yard looks like. So it’s just a matter of time and knowledge now.”