Stay-Put Paving Sand

It looks like ordinary, free-flowing sand, and that’s how it behaves when you put it down.

Written and Photos by: Steve Maxwell

There are dozens of gorgeous new paving brick products hitting the market each year, but with the added beauty and diversity comes a problem. Many of these high-end bricks owe their good looks to a more rounded, irregular shape, especially around corners and edges. While this looks terrific, it also means larger spaces between installed bricks, and a much greater chance that the sand between them will get washed away by rain and melt water.

Polymeric sand is one solution that I know works well because I’ve used it and watched the results over the last three years. Open up the bag and it looks like ordinary, free-flowing sand, and that’s how it behaves when you put it down. But unlike regular sand, the polymeric product firms up in reaction with water. It sounds good and it is, but there are challenges to installing it properly and limitations you need to know about before you begin.

If you’re installing poly sand in a new paving brick installation, there’s nothing different you need to do while putting the bricks down. If you have an existing surface that had ordinary sand applied originally, you’ll need to clean out all the gaps with a pressure washer. You must create a perfectly clean situation, and you also need to be careful. There are two things to worry about, and the first is the bricks themselves.

If you hit your pathway with the pressure washer wand too close to the bricks, it will leave permanent marks that won’t become apparent until after the water dries. How close is too close? That depends on the pressure output of your washer and the shape of the wand tip. Begin with the wand 12 inches away from the pathway surface, and adjust the distance from there. Aim to have just enough power delivered to clean out the gaps, but no more.

Another issue is dirt spatters. The sand that flies out from between brick gaps makes a big mess on surrounding decks and walls, but it washes off easily as long as you do it while the dirt is still wet. If it dries, you’ll need to scrub to remove the mess.

The main thing to understand about poly sand is that it must be installed on a perfectly dry pathway.

Remember, this stuff is activated by water, and it turns quite gooey with even a little moisture. You need bone-dry conditions, with no chance of rain for a day. Don’t start without the green light from the weatherman.

Spreading poly sand begins the same as with regular sand. Pour a thin layer as smoothly as possible over the whole pathway surface, and then use a stiff-bristled push broom to spread the sand around and begin working it into the gaps. The trick is to go beyond the broom with a gas-powered vibrator afterwards. This jiggles the sand deep down into the gaps, an essential part of any long-lasting installation. The broom alone might seem to do a good job, but don’t be fooled. It actually leaves behind hidden gaps that will lead to sand collapse later. Don’t skip the compactor.

With all brick gaps fully filled with poly sand, you’re about to face the most important part of the
job: pre-activation cleaning. Since poly sand turns goopy when wet, you must have the surface of the
bricks completely and absolutely clean before applying water. Any sand remaining on the surface
will mar the appearance of the brick, so be diligent. Use a soft-bristled broom to move all remaining surface sand into the gaps, going over the surface at least twice, just to make sure.

Now it’s time to activate the sand. Success requires finesse. You need to gently apply a fine spray of water to moisten the sand, but not so much that it moves any sand up and out of the brick gaps.

It’s a fine balance, so be careful. After an initial misting, let the sand begin to firm up for 15 or 20 minutes, then add more water while watching carefully. Before you’re done, you need to apply
enough water to wet the entire depth of the brick gaps.

This could take three or four or five wettings, but be careful. The danger is that if you apply water too fast, it will wash the surface sand out of the gaps and onto the bricks. When you think you’ve wet the surface enough, take a framing nail or three-inch deck screw and burrow down into a joint gap just to be sure. If it’s not wet all the way, keep up the misting and pausing cycle.

One of the unique features of poly sand is that it gets soft again when moist. This allows it to reshape itself into brick gaps, always creating a crack-free appearance. You can also apply a new layer of sand as areas settle or get washed away slowly over the years. New sand fuses to the old seamlessly.

Polymeric sand isn’t foolproof, and it doesn’t eliminate all the problems encountered with regular
sand, but it’s still more than worthwhile. Use it to get the most of your new paving brick installation, and you’ll spend more time enjoying the look and less time working to keep it up.