Sinking patio stones and paving bricks are a common problem in Canada because the freezing and thawing temperatures we get cause more soil settling than experienced in frost-free regions. Regardless of the cause, the solution is the same:
- lift the stones
- add sand
- compact it
- then replace the stones
It’s a trial and error process, especially as you’re getting used to the task, but it does work well. The trick is getting the first stone lifted when you can’t get your fingers underneath. A metal coat hanger bent to 90º makes a good tool for lifting paving stones, though you’ll usually need something stronger for raising the larger patio stones. A small pry bar with a thin tip is useful for lifting stones, too. Be sure to compact the sand as much as you can before replacing the stones, to avoid future settling.