Building cantilevered pergola advice

4791 Views 6 Replies 3 Participants Last post by Nealtw, Mar 4, 2020

kgkern01

Discussion Starter · Mar 4, 2020

I am building a 16x20 ground level deck with beam supports in 2' concrete on the corners and middle beams. I want to build a cantilevered pergola on one side of the deck, posts total 18' apart with a 3rd post in the center. I plan on using 6x6x10 posts set in 3' deep x 12" concrete, with the beams 2x8x10's sandwhiched on each side of the beam, 3' on back side of beam, 7' out over the deck. 6x6 beam supports at 45* supporting the 7' side from 3' away from the posts. I plan on using around 7 2x6x20's for the rafters. Also, the 3 deck beams will attach to these posts as well at the ground level, so that will be more weight keeping the posts in place. My question is regarding the back side cantilever support. I initially thought about using 6x6 or 4x6 going from the 3' back side of the beam to 2/3 way down the post to support the cantilever side. However I was thinking that using steel support cables anchored into the post footings might be a stronger option? If so, what kind of cable should I use to anchor the cantilever? I plan on starting the build tomorrow.

Thanks in advance for the advice!

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Nealtw

· #2 · Mar 4, 2020

kgkern01 said:
I am building a 16x20 ground level deck with beam supports in 2' concrete on the corners and middle beams. I want to build a cantilevered pergola on one side of the deck, posts total 18' apart with a 3rd post in the center. I plan on using 6x6x10 posts set in 3' deep x 12" concrete, with the beams 2x8x10's sandwhiched on each side of the beam, 3' on back side of beam, 7' out over the deck. 6x6 beam supports at 45* supporting the 7' side from 3' away from the posts. I plan on using around 7 2x6x20's for the rafters. Also, the 3 deck beams will attach to these posts as well at the ground level, so that will be more weight keeping the posts in place. My question is regarding the back side cantilever support. I initially thought about using 6x6 or 4x6 going from the 3' back side of the beam to 2/3 way down the post to support the cantilever side. However I was thinking that using steel support cables anchored into the post footings might be a stronger option? If so, what kind of cable should I use to anchor the cantilever? I plan on starting the build tomorrow.

Thanks in advance for the advice!

Let's start at the bottom. Do you have frost depth in the area where you live, anything like this that you build like this the bottom of the concrete and post have to be deeper than frost.

How high off the ground will the deck be?

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kgkern01

Discussion Starter · #3 · Mar 4, 2020 (Edited)

Nealtw said:
kgkern01 said:

I am building a 16x20 ground level deck with beam supports in 2' concrete on the corners and middle beams. I want to build a cantilevered pergola on one side of the deck, posts total 18' apart with a 3rd post in the center. I plan on using 6x6x10 posts set in 3' deep x 12" concrete, with the beams 2x8x10's sandwhiched on each side of the beam, 3' on back side of beam, 7' out over the deck. 6x6 beam supports at 45* supporting the 7' side from 3' away from the posts. I plan on using around 7 2x6x20's for the rafters. Also, the 3 deck beams will attach to these posts as well at the ground level, so that will be more weight keeping the posts in place. My question is regarding the back side cantilever support. I initially thought about using 6x6 or 4x6 going from the 3' back side of the beam to 2/3 way down the post to support the cantilever side. However I was thinking that using steel support cables anchored into the post footings might be a stronger option? If so, what kind of cable should I use to anchor the cantilever? I plan on starting the build tomorrow.

Thanks in advance for the advice!

Click to expand...

Let's start at the bottom. Do you have frost depth in the area where you live, anything like this that you build like this the bottom of the concrete and post have to be deeper than frost.

How high off the ground will the deck be?

I’m framing it with 2x8’s so it will be maybe 10” off the ground. I live just outside of Louisville KY, the frost depth here for posts is 2’. I built a privacy fence here 10 years ago, posts at 2’ and have no visible heave or leaning of the fence still.

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huesmann

· #4 · Mar 4, 2020

A sketch would sure help. I'm having trouble picturing your intent. If you're using 10' posts, sunk 3' into footings, that's only 7' above the ground. I'm assuming your deck is actually above ground, and not countersunk. That means you will have maybe 6' of post sticking up. Is that enough head room?

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kgkern01

Discussion Starter · #5 · Mar 4, 2020 (Edited)

That's a good point about the height clearance, I may just get some 12' 6x6's instead, and cut 1' off the top. I plan on having a slight incline to the roof of the pergola, and planning something like this, but with 3 posts instead of 2. In this pic they are using 4x6's on the back for the cantilever brace, but I figured 6x6's would be stronger and help counter weight, or I could add anchors into the cement and use cables on the back side if I would need more than bolted in 6x6's to anchor the back side?

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Nealtw

· #6 · Mar 4, 2020

kgkern01 said:
That's a good point about the height clearance, I may just get some 12' 6x6's instead, and cut 1' off the top. I plan on having a slight incline to the roof of the pergola, and planning something like this, but with 3 posts instead of 2. In this pic they are using 4x6's on the back for the cantilever brace, but I figured 6x6's would be stronger and help counter weight, or I could add anchors into the cement and use cables on the back side if I would need more than bolted in 6x6's to anchor the back side?

So If I understand it the deck would be either free standing or attached to the house with a ledger on the left of my drawing.

So the deck plan would be something like this.