Pergolas are popular options for decks, because they help define this area or your outdoor space without confining it. A pergola offers no protection from the sun, rain or snow, but it adds dimension to your space, giving your deck a comfortable, intimate feel. A pergola can also be used for trailing vines and hanging planters. Building a pergola is a time-consuming task, but if you have a helper, you can likely finish this project in one or two weekends.
Lay out a pair of 4-by-4-inch posts the width of your pergola. Nail or screw together a pair of 2-by-10-inch boards to achieve a double thickness. Place the double 2-by-10 between the 4-by-4 posts, flush with the top edges of the post. Use a carpenter's level to make sure the corners are square. Using nails or wood screws, connect the corners with toenail joints (driving the screws or nails in at a 45-degree angle). This will form one support post section of your pergola. Repeat this process to create the support section for the other end. If your pergola will be longer than 8 feet create additional support sections to place between the ends.
Attach post brackets large enough to accommodate 4-by-4 posts to the surface of your deck. The brackets should be placed directly over the support posts and piers that anchor your deck to the ground.
Erect the support sections of the pergola, attaching them to the post brackets installed on your deck. Nail or screw together two sections of 2-by-10 lumber to run the length of your pergola on each side. Attach these double-width sections to your support posts, flush with the tops of the posts. Check again to make sure the corners are square, and place a level on each of the top support beams to ensure that the structure is level.
Cut sections of 2-by-10 lumber 4 to 8 inches longer than the length between your outer support posts. Using a jigsaw, cut 2-inch-deep-by-4-inch-wide notches in these boards where they will meet the support beams. Lay the notched boards lengthwise across the top of your pergola's supports at 8-inch intervals. Attach these crossboards to the support beams with wood screws.