How to Build a Timber Pergola
Some pergolas have angled roofs, but flat-roofed ones are easier to build.
It won't protect you from getting pummeled during a spring rainstorm, but a pergola most certainly will add some interest and shade to your yard. The simple structure typically is built with pressure-treated timbers to ensure it will be the site of many outdoor cookouts and leisurely afternoons for years to come. Although you could build a pergola on your own, an extra set of hands will definitely help.
Mark a 10-foot square where you will build the pergola, snapping a chalk line on the ground to designate the square. When the structure's support posts are set in the ground, they'll be 10 feet from each other.
Dig one 40-inch-deep hole in the ground at each of the square's four corners by using a post-hole digger or auger. Your posts will be 6 inches wide. Make each hole accordingly so that the edge of each corner post will be 10 feet from the edge of the next corner post.
Pour a 2- to 3-inch-deep layer of gravel into the bottom of each hole. Set a 6-inch-by-6-inch-by-10 1/2-foot long post into each hole. Fill the remainder of each hole with quick-setting concrete and water, using the proportions indicated on the bag of concrete.
Hold a level against each post to ensure it stands level. Chances are good that the posts will need help standing up straight as the concrete dries. Keep them in place by nailing one end of a piece of scrap 2-by-4-inch wood, which is about 5 feet long, against the middle of each post and allowing the other end of each 2-by-4 to rest on the ground. Nail a second 2-by-4 to the opposite side of each post, and allow it to rest on the ground. The 2-by-4s will act as braces as the concrete dries. Wait for the concrete to dry, and take down those 2-by-4s.
Hold a 2-inch-by-8-inch-by-12-foot wood board near the top and outside of two adjacent corner posts, with 1 foot of overhang on each post. Drill 3-inch-long galvanized deck screws through the 2-by-8 and into the posts to hold the 2-by-8 in place temporarily. Secure a second 2-inch-by-8-inch-by-12-foot wood board in place to the opposite side of the same posts by using 3-inch-long galvanized deck screws. The 2-by-8s are the headers that will hold the pergola joists in place.
Drill a 5/8-inch-diameter hole through the header board on the outside of the two corner posts, drilling through each of those posts and then through the header board on the inside of the posts. The holes should be about 1 inch from the top of the posts. Drill a second hole about 1 inch below each first hole and slightly offset from each first hole to add stability. Repeat this process on the other side of the header. Install a third header board and a fourth header board, each 2 inches by 8 inches by 12 feet, on the opposite side of the pergola, and drill 5/8-inch-diameter holes through the headers and posts on that side of the structure.
Drive one carriage bolt, which is 11 inches long and 5/8-inch thick, through each of the holes from the pergola's outside to its inside. Set a washer and nut on the end of each carriage bolt, and secure them to the bolt tightly using a wrench. Remove the screws you installed to hold the headers in place temporarily.
Mark the center point of each outer header. Use your measuring tape and a pencil to find and mark the centers.
Lay the first 2-inch-by-8-inch-by-12-foot rafter across the center of the header, where you made a mark. The rafter should rest on its short, 2-inch end, with about 1 foot of its excess length hanging over the headers on two sides of the pergola. Secure the rafter to the headers by inserting 3-inch-long screws through the rafter board and into the headers at an angle.
Measure 16 inches to the left or right of the first rafter, and install a second rafter in the same way that you installed the first one. Continue adding rafters 16 inches apart from one another along both sides of the pergola's top, resulting in a total of nine rafters spanning from one side to the other side.
Mark the exact center of the two outermost rafters by using a pencil. Lay a 2-inch-by-4-inch-by-12-foot long wood board on its 2-inch side from the center mark on one outermost rafter to the center mark on the other outermost rafter. Secure the board to the rafter by inserting a 2-inch-long galvanized deck screw through it and into the rafter. The board you just added is a "rafter stay."
Measure 2 feet from each side of the first 2-by-4 "rafter stay" you installed, and install a second and third rafter stay in those locations. Measure 2 feet from those rafter stays, and install a fourth and fifth rafter stay at those spots.
Things You Will Need Measuring tape Chalk line Post-hole digger or auger Gravel 4 timber posts, each 6 inches by 6 inches by 10 1/2 feet Quick-setting concrete Container Level 8 scrap wood boards, 2 inches by 4 inches by about 5 feet Hammer Nails Drill 13 wood boards, each 2 inches by 8 inches by 12 feet Galvanized deck screws, 3 inches long 5/8-inch drill bit 8 carriage bolts, 11 inches long, 5/8-inch thick Carriage bolt nuts Carriage bolt washers Wrench 5 wood boards, 2 inches by 4 inches by 12 feet Galvanized deck screws, 2 inches long Tips In order to give pergolas some flavor, people often cut curved lines into the ends of the headers and rafters. If you decide to do that, cut the shapes in a uniform manner, and do it before you put up the headers and rafters.If you are building a pergola on a patio or other surface that makes it difficult to sink the posts into the ground, an option is to use post anchors. They are basically large blocks of concrete with fittings on the top, allowing you to set posts on them. If you go that route, follow the post anchor manufacturer's instructions carefully to ensure you install the posts safely.About the Author
Nicole Vulcan has been a journalist since 1997, covering parenting and fitness for The Oregonian, careers for Career Addict, and travel, gardening and fitness for Black Hills Woman and other publications. Vulcan holds a Bachelor of Arts in English and journalism from the University of Minnesota. She's also a lifelong athlete and is pursuing certification as a personal trainer.
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