"Make sure the patio is big enough," says landscape architect Paul Maue. "Getting the scale right is the hardest thing—you always need more space than you think." Try setting up a table and chairs on the lawn first to see how much room they need. Maue's rule of thumb: Allow 25 square feet per person for a seat and room to move.
Consider a change in grade
A step up or down by just a few inches can make a small yard seem larger and break up the expanse of a large yard, making it more interesting.
Prepare a proper base
After determining the finished grade of the patio, TOH landscape contractor Roger Cook removes enough loamy material to allow for 8 to 10 inches of compacted gravel, topped with about 1 inch of stone dust. Because bluestone is variable in thickness—from 1 1/2 to 2 1/2 inches—Roger mixes 10 parts stone dust to 1 part cement and wets it till it's the consistency of thick mud. "This helps settle the stones in and fill any gaps on the underside," he says. Once the stones are in place he'll brush more stone dust between them to lock them in place—where winters bring snow and ice, frost heaves will crack a patio that's been mortared in with concrete.
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.