Perkin' Up the Patio

Paul James repairs a flagstone walkway, replacing loose gravel with a polymer sand.

Gardening by the Yard : Episode GBY-1503 -- More Projects »
Gardening by the Yard host Paul James put in a flagstone patio about two years ago. On balance, he's pleased with the way it turned out, but over time a design flaw has become more and more apparent.
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Figure A
Between the stones he had applied a layer of crushed gravel. Every time he uses his blower to remove leaves and twigs that fall from the tree above, little pieces of gravel fly all over the place (figure A), and that stray gravel does a real number on bare feet.
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Figure B
So he's going to try a new material between the stones. It's a special polymeric sand (figure B), and according to the manufacturer, it sets up somewhat like concrete but is flexible enough to resist cracking. One bag of the sand covers between 50 and 100 square feet, depending on the width and depth of the joints.
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Figure C
To prepare the site, Paul blows as much of the gravel out of the joints as he can. He then spreads a bag full of the sand over a given area and uses a stiff broom to sweep it into the joints between the stones (figure C). He adds more sand as needed until the entire patio is covered. Finally, he tidies up by gently blowing any excess sand away with a blower.

The next step is to water the area well. He uses a fine mist from his hose (so the sand doesn't wash away). This activates the polymer in the sand and begins the hardening process.

About five minutes later he waters again. This time he uses a bit more hose pressure. And after another five minutes, he waters one last time, again using more hose pressure.

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Figure D
After the last watering, Paul checks to make sure the sand is thoroughly wet (figure D).

After 48 hours, the polymer will set up completely and the joints will be able to stand all kinds of foot traffic.