Cantilevered Pergola -- DIY Designed and Built

1 Material
1 Week

Read about our self-designed and built cantilevered pergola built for around $400.

Cantilevered pergola over part of our deck

We just had a new composite deck installed and wanted a pergola to cover a portion of it. My husband, Craig, designed this one and set to work with just the plans in his head. It is cantilevered, thus supported by two legs on the outside of the deck, in order to be more sturdy and stable than one attached to the top of the deck. It is attached to the side of the deck as shown in my blog post. No kits were available for this type of deck, so he purchased the materials from a nearby lumber yard.

When the deck was being built, we had the contractor attach two 24-inch all-thread bolts into the deck’s foundation so he could use these to anchor the two legs of the pergola. In the photo above, you see one of those bolts sticking out from the side of the deck (bolt is just above the far-left end of the lattice in the lower portion of the photo above…just to the right of the center).

The second foundation all-thread bolt is shown above between the little strip of lattice and the steps on the right side of photo. Craig would use these two bolts to attach and stabilize the main support legs of the pergola.

He’d pre-drilled the hole in the lower portion of these support legs and slid them onto the large all-thread bolts that extended from the deck. He’d previously dug-in two 6-inch post footers directly underneath the all-thread bolts. The support legs and first braces go up. Craig had pre-drilled most of the holes for the carriage bolts and lag screws.

Additional supports are added to serve as counter-weights since the rafters extend 7' over the deck without supports on the other end.

Notches were cut on both ends of the cross-pieces. He used carriage bolts and lag screws to connect all of the supports.

Once the seven rafters were in place, Craig measured the distance between them and moved them as necessary to even out the spaces at roughly 16″ on center. He toe-nailed a 3″ exterior wood screw into each of the seven rafters on the outside notches to secure them.

Later he added 10 8′ 2″ x 2″s to provide a little extra shade and additional support for vines to cling to in the future. (see last photo below)

He spent $400 on materials. Kits for traditional pergolas begin around $800.

See additional photos in the Comment area.

Materials List Item Quantity 6” x 6” x 10′ pressure treated post 2 4” x 6” x 10′ pressure treated post 3 2” x 8” x 10′ pressure treated board 4 2” x 6” x 16′ pressure treated board * 7 1/2” x 10” carriage bolt 20 1/2” nut and washer for carriage bolt 20 1/2” x 8” lag screw 20 1/2” x 6” lag screw 4 6” post foot 2 Concrete for 2 post footings Total with delivery ~ $400** * Note: number of 2” x 6” x 16′ boards may vary from 7 – 10 depending on desired spacing between rafters. We used just 7 for rafters 16” on center. My husband pre-drilled holes in the boards and laid them on the garage floor in the manner in which they would be put together. He could also mark the angles for his cuts for the smaller support pieces with everything on the ground. I hope this helps anyone who might be interested in building this pergola.

We added commercial globe string lights from Save-on-Crafts so we can enjoy the deck at night.

Craig later stained the pergola and planted non-invasive American wisteria in pots next to each post. Here you see it in 2018 (pergola built in 2015) after we redesigned the screen porch, had the house re-sided and cut down the giant cedars that were blocking the view of the southern Virginia mountains.

Suggested materials:

  • See materials list in the Comments section along with additional photos

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Have a question about this project?

3 of 19 questions
  • German Delgado
    on Sep 5, 2019

    Hello there, amazing design. I actually did something similar with legos when I was a kid! Never occurred to me to apply it in 1 scale! 🤗

    my question, any particular reason why you guys used 14 degrees of tilt?

    Could you tilt upwards more?

    Am in the process of building a walkway about 30 feet long and am going to go with this design.

    Thank you!!

    • German Delgado
      on Sep 7, 2019

      Thank you ma’am for the info. Congrats on the design, It not only obeys the laws of Physics it looks great as well.

      Much planning to be done, I got to figure out how big and deep my concrete bases need to be to keep from tilting over time. The great thing about your design is that it helps balance the weight it also can get very windy over here!

      just a lot of things to consider but I will Definitely post some pictures.

  • Tom
    on Apr 28, 2020

    Thanks for sharing this has inspired my build. I understand 24" of threaded rod secured the cantilever 6x6's to the deck foundation. When you say "dug in" do you mean you poured a shallow concrete footing then used strong ties to attach the post bottoms to the footing?

    • Sue P.
      on Apr 28, 2020

      Yes, that's right. We have a septic tank in that area so had to do it this way.

  • John Waide
    on Jun 12, 2020

    Thank you for sharing your project. You did a great job and the pergola looks great Do you think you could have used 4 x 4 posts?

    • Sue P.
      on Jun 12, 2020

      Thank you for your kind words. My husband said he would not recommend 4 X 4 posts because of the weight they are supporting. He also thinks it would look unbalanced.

Join the conversation

2 of 51 comments
  • Yalmer
    on May 11, 2020

    Thank you for your response....I am planning a distance between 6x6 post of 11 to 12 ft....where the 4 1/2 x 6' lag bolts are placed?

  • Yalmer
    on May 14, 2020

    Thank you for your response....I am planning a distance between 6x6 post of 11 to 12 ft....where the 4 1/2 x 6' lag bolts are placed? material needed list 20 1/2 x 10 bolt, can see 8 used plus 2 to fix 6x6 to deck...

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