A good part of the detail on the freestanding pergola shown in slide 4, and much of its stability, are found in its four corners, where the tops of the posts are wrapped with two sets of interlocking beams that have rafter tails. Here, David Valcovic of Trellis Structures—This Old House landscape contractor Roger Cook's go-to guy for custom pergolas—shows how to make this long-lasting connection:
1. Where beams cross on the outside corner of the post, notch them about halfway through—one from the top, the other from the bottom—so they fit together with the tops flush.
2. For beams that meet at the inside corner of the post, cut off the rafter tails to the same length as the ones extending off the first set of beams. Notch beams halfway through where they meet at the post's inside corner; they should fit together with the tops flush.
3. Route ½-inch-deep slots in the outside faces of the first set of beams to accept the second set's decorative rafter tail pieces; this will keep them from visibly pulling away when the temperature changes. Glue and screw the pieces in place. —SAL VAGLICA