The beauty of a freestanding pergola, like this one, is you don't have to anchor it to the house or move gutters. That said, here are a few things to consider.
Posts are typically sunk 2 to 3 feet deep, depending on the pergola's height, and set in tamped gravel. A skirted base provides a finished look.
Options for posts, rafters, and purlins include treated lumber, easy-care vinyl-clad aluminum, and composite made from wood and plastic.
Purlins provide some protection from the sun, but for more coverage you can add a canopy of leafy vines or climbing roses, woven bamboo mats, sailcloth, or polycarbonate panels.