How to build a trellis patio roof

Written by james j. siegel
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How to build a trellis patio roof
One example of a patio pergola with a trellis roof. (windows,arbor image by Greg Pickens from

If you want to give your existing patio a little bit of shade, try your hand at adding a trellis-style roof. One way to add this roof is by installing a pergola. A pergola will consist of four posts at each corner of the patio. The posts will hold up a series of beams and crossbeams, along with several roof slats that will look like a trellis. Not only will the trellis provide some shade, but the structure will give your patio the feel of an outdoor room that will be perfect for gatherings or just relaxing.

Skill level:

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Things you need

  • Wood stakes
  • Shovel
  • Gravel
  • Concrete mix
  • Trowel
  • 4 wood posts, 4 x 4 inches and 10 feet long
  • 8 wood beams, 2 x 8 inches and 8 feet long
  • Ladder
  • Tape measure
  • Pencil
  • Nails
  • Drill
  • Carriage bolts
  • 8-foot-long wood joists (2 x 6 inches)
  • Assistant

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  1. 1

    Measure out the dimensions of the existing patio. For this example, the patio will be six feet by six feet. Drive a wooden stake into the ground at each corner of the existing patio and make sure they are equal distances apart. Each stake will mark the placement of each pergola post.

  2. 2

    Remove each stake one at a time and dig a two-foot-deep hole. Then place a 10-foot-long beam in each of the holes. Add six inches of gravel around each of the posts. Make sure the posts stay completely upright.

  3. 3

    Mix concrete and pour it into each of the holes. Pour the concrete until it reaches the soil line. Then smooth the wet concrete with a trowel and let it dry for 24 hours.

  4. 4

    Mark the placement of the beams that will be installed at the top of the posts. Climb a ladder to the top of each post. On the left and right hand side of each post, measure down 7.25 inches. Mark this spot with a pencil.

  5. 5

    Climb the ladder again and place one of the eight-foot-long beams right under the spot you marked with a pencil. Place the eight-inch side of the beam against the post. You will need an assistant on another ladder to hold the other end of the beam in place. Allow the beam to reach over the side of the posts by one foot. Drill two holes through one end of the beam and into the post. Secure the beam to the post with a carriage bolt. Drill two more holes through the end of the beam that your assistant is holding. Secure that side as well with a carriage bolt.

  6. 6

    Repeat step five on the opposite side of the two posts you just worked on. If you added the beam to the left-hand exterior side, add another beam to the left-hand interior side. Allow the beam to reach over the side by one foot, drill two holes on each side, and secure with carriage bolts. Once you are finished, the two posts on the left-hand side of the patio will be sandwiched between two beams.

  7. 7

    Repeat steps five and six on the right hand side of the patio. Install two beams on the interior and exterior of the posts. Allow each beam to hang over the side by one foot. Drill two holes through the end of the beams and into the posts. Secure with carriage bolts on each end. Remember to have an assistant on the opposite side to hold the beams in place.

  8. 8

    Add four crossbeams to the front and back of the patio. With an assistant helping you, lift one of the eight-foot-long crossbeams up to the front of the pergola. Place it above the 7.25-inch mark and let it hang over each side by 1 foot. As with the previous steps, drill two holes through the ends of the crossbeam and into the post. Do this on the exterior and interior side of the front and back of the patio. When you are finished, it should look like the four posts are holding up a square.

  9. 9

    Run a series of wood joists from the front crossbeams to the rear crossbeams. The joists are nailed at an angle through the slat and into the crossbeams. Place the 2-inch length side of the joist against the crossbeams. Allow the joists to also hang over the side of the crossbeams by 1 foot. Start at one end of the pergola and keep adding joists until you reach the other end. With this example, you have six feet of space to add joists. If you space the joists six inches apart, you can add 12 roof joists. The more joists you add, the more shade the trellis roof will provide.

Tips and warnings

  • When purchasing wood for the project, consider using cedar. Cedar has natural properties that will repel bugs and prevent them from eating or burrowing into the wood.
  • You can also consider planting crawling vines and other plants at the base of the posts. These plants can crawl up the posts and twist around the trellis roof.
  • Always wear safety goggles when working with a drill or nails.

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