Preplan for Irrigation: If irrigation or outdoor lighting systems aren't fully in place, Roger runs pairs of PVC pipes in the patio's base. "That way you can come back later and run water lines or electrical conduit without disturbing the hardscape," he says. Just be sure to mark the pipes' location with stones or to note it on the plan.
Get the Pitch Right: "The last thing you want is standing water," says Roger. To encourage runoff, slope the patio away from the house, 1/8 inch per foot. Stones also need to be level to each other for a smooth, stable walking surface. So before he begins, Roger runs two sets of string lines about 1/8 inch above the finished surface. To establish the grade, he sets control lines on either side of the patio, leveling them to each other and checking the slope. Then he sets up a header line along the edge closest to the house; this establishes a starting level line for laying the stone. He runs another string line 4 feet from the header, so he can use a 4-foot level to check each stone as it's laid. With that row complete, he runs another "set line" 4 feet down—and so on, until the entire surface is paved.