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Pergola connection question

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Forum topic by Derrick posted 06-24-2019 02:57 PM 314 views 0 times favorited 16 replies Add to Favorites Watch
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Derrick

103 posts in 1554 days


06-24-2019 02:57 PM

Hello,

We’re getting closer to putting up a pergola in our backyard. It’ll be a free standing triangle/corner type. Right now I’m torn on the design. Mostly because I’m not 100% sure on one of the connections.


This is the one I’m leaning towards currently, but it’s only because of the ease of all the connecting pieces. The design is pretty cut&dry, and I could make it work in our backyard with few adjustments


From these plans: http://myoutdoorplans.com/pergola/corner-pergola-plans/ This one is a style that I think suits us better. The big difference is the beam(hopefully that is the correct term), that forms the hypotenuse. That’s the portion I like. That connections is also the one that I’m least confident in.
The plans call for a couple timber bolts at each 45* end. I have no idea what the strength of any kind of bolts is, it just feels like a lot of weight supported by those bolts.

I’m working with full dimension(6×6) Alaskan yellow cedar for the posts/beams The posts of our triangle are 12’ apart(outside dimension). If my math is close, that puts the hypotenuse beam at 16+ feet. That seems like a ton of weight to be supported by 4 timber bolts. And that’s not even with anything mounted on top of it. Am I wrong for feeling this way? Should the ends be resting on the posts for more support? I could notch out the other two beams where they connect with the hypotenuse, and that would allow it to rest on the posts, and also be bolted to the other beams.

Is there a better way that would make me feel safer about all of that weight over head, or am I over thinking it, and it’ll be fine?

I’m open to all ideas. The only thing that we’re sure on is that it will be a triangle. That 4th leg would really cut things off in our already small back yard.

Any help would be awesome.

Thank you.

Derrick


16 replies so far

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Phil32

579 posts in 319 days


#1 posted 06-24-2019 03:08 PM

I’m surprised you are using Alaskan Yellow Cedar for this project. As a woodcarver, I hate to see an increasingly rare carving wood used for an outdoor structure. But that is your choice. I will not comment on the engineering aspects of your project.

-- Phil Allin - There are mountain climbers and people who talk about climbing mountains. The climbers have "selfies" at the summit!

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Derrick

103 posts in 1554 days


#2 posted 06-24-2019 03:46 PM



I m surprised you are using Alaskan Yellow Cedar for this project. As a woodcarver, I hate to see an increasingly rare carving wood used for an outdoor structure. But that is your choice. I will not comment on the engineering aspects of your project.

- Phil32

Oh damn. Didn’t know that. I have a Mill local to me, and they have a ton of it. Well, that makes me feel terrible.

View torus's profile

torus

299 posts in 829 days


#3 posted 06-24-2019 06:38 PM

It may does not fit with your design, but I would use 2×8 instead of beams.
BTW The picture above does not have beam in place of hypotenuse.

-- "It's getting better..." - put this on my RIP stone!

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Knockonit

582 posts in 618 days


#4 posted 06-24-2019 06:57 PM

any free standing structure, with connections at bottom on slab or grade, becomes a pivot point, as will the inside post of triangle, best to have decent side beam post seats, anchored well and up post quite a ways to negate the shake and rattle syndrone one it begins to dry out some. Use a beam seat at top of rear post and opposing other two posts with mechanical connections, will help stiffen system for the shake. Nature of best without posts or fastening at lower point there is no diaphram to keep it rigid.

building free standing units such as this is and always has been a pia,

best of luck
Rj

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Derrick

103 posts in 1554 days


#5 posted 06-24-2019 07:31 PM

Well, it’s clear I need to do better with my clarity of the terminology. By free standing, I meant that it wouldn’t be against the house on a ledger board or anything like that. We just had a new concrete slab poured, and I had planned on using OZCO’s 6” post bases. They sit on top and are bolted to the slab.

Hopefully that clears up some of this.
I’ll dissect the rest of what is being said.

Thanks to everyone that has responded!!

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Derrick

103 posts in 1554 days


#6 posted 06-25-2019 01:22 AM

Here is one that is a lot closer to what we are going for.

On this one, it still looks like the hypotenuse beam is held in place by the timber bolts. That just seems like a ton of weight.

Is that an unsafe practice?

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Derrick

103 posts in 1554 days


#7 posted 07-01-2019 10:44 PM

So, I think this is the design we’ll go with.

I don’t have any specs on this picture, but I was planning on using my full dimension 6×6’s for the posts. We have the brackets that sit on top(bolted down)of the concrete for the bases.

I was thinking of 2×10 beams sandwiched on the notched posts.

Then 2×8’s for rafters. Would 2×8’s look ridiculous for the rafters in this situation? Should I use 1x material instead?

Should I utilize knee braces into this design as well?

Sorry about all the questions.

View ibewjon's profile

ibewjon

679 posts in 3209 days


#8 posted 07-01-2019 11:01 PM

2x. Thinner will twist like a pretzel.

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ibewjon

679 posts in 3209 days


#9 posted 07-01-2019 11:02 PM

2x. Thinner will twist like a pretzel.

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Derrick

103 posts in 1554 days


#10 posted 07-01-2019 11:10 PM



2x. Thinner will twist like a pretzel.

- ibewjon

Good point. Would knee joints be needed in this situation, or is that something that I won’t know until I get everything else in place?

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therealSteveN

3056 posts in 990 days


#11 posted 07-01-2019 11:54 PM

Portland Bolt torque chart, note different grades of bolts used.

To really make use of this you would need to bare minimum talk to them, or whoever you plan to source your hardware from. I don’t know if they will comment on your build, probably they would suggest you have an architect look at the plan, the hardware, and compare it to the location you plan to build. Winds vary all across the land, and if it’s outdoor, they will matter.

But sure as the Sun will rise, bolts, and other mechanical fasteners are used daily in structure a lot bigger than what you are talking about. It’s possible to BORG source the strength you need, I just wonder if they would have the length?

As to 1x or 2x, If you have the beams already, stop and pick up a single 1x, and a 2x. Just lay them next to that 6×6, and you will quickly grab the 2x as the winner. I’d say based on the size if 16’ covers your front, that you will be choosing 2×8’s. or 2×10’s and I think the 10’s will look better.

It’s a fact that locality matters. Phil is shocked you are using a wood he treasures for carving, however it’s local to you. I have heard about “Walnut barns” where every stick was Walnut. I’ve never seen one though. what I have seen over and over in Ohio is barns made out of ALL the local woods. Because they were there, and their builders just went tree to tree, felled it, and started turning it into barn parts. Sure some woods are treasured more for one feature than other woods, but it was local, it was the cheapest way to do it.

Your use is exactly the same. If the wood is legally sold and traded, and that is what is local, use it without remorse. Alaskan Yellow Cedar

-- Think safe, be safe

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Derrick

103 posts in 1554 days


#12 posted 07-02-2019 12:31 AM



Portland Bolt torque chart, note different grades of bolts used.

To really make use of this you would need to bare minimum talk to them, or whoever you plan to source your hardware from. I don t know if they will comment on your build, probably they would suggest you have an architect look at the plan, the hardware, and compare it to the location you plan to build. Winds vary all across the land, and if it s outdoor, they will matter.

But sure as the Sun will rise, bolts, and other mechanical fasteners are used daily in structure a lot bigger than what you are talking about. It s possible to BORG source the strength you need, I just wonder if they would have the length?

As to 1x or 2x, If you have the beams already, stop and pick up a single 1x, and a 2x. Just lay them next to that 6×6, and you will quickly grab the 2x as the winner. I d say based on the size if 16 covers your front, that you will be choosing 2×8 s. or 2×10 s and I think the 10 s will look better.

It s a fact that locality matters. Phil is shocked you are using a wood he treasures for carving, however it s local to you. I have heard about “Walnut barns” where every stick was Walnut. I ve never seen one though. what I have seen over and over in Ohio is barns made out of ALL the local woods. Because they were there, and their builders just went tree to tree, felled it, and started turning it into barn parts. Sure some woods are treasured more for one feature than other woods, but it was local, it was the cheapest way to do it.

Your use is exactly the same. If the wood is legally sold and traded, and that is what is local, use it without remorse. Alaskan Yellow Cedar

- therealSteveN

That’s a ton of useful info. Thank you for that!!

Right now I only have the posts. I was just talking to my wife about about picking up the rest of the lumber after this weekend. I got a rough idea on all the hardware. I just need to finish sourcing it.

View ibewjon's profile

ibewjon

679 posts in 3209 days


#13 posted 07-02-2019 03:43 AM

Some or even all of the buildings at Ft. Scott in Kansas are framed and built of BLACK WALNUT, As stated, it was the wood that was available locally in the 1800’s.

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Derrick

103 posts in 1554 days


#14 posted 07-02-2019 04:28 AM

I think Phil was referring to topics like this: https://www.latimes.com/nation/nationnow/la-na-nn-alaska-yellow-cedar-20150410-story.html in regards to my use of AYC. I had never even thought of something like this when I started.

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CarlosInTheSticks

366 posts in 788 days


#15 posted 07-02-2019 05:50 AM

Thats a very nice plan you have chosen to go with Derrick, I don’t see any weakness in the design. However IMO I don’t think it matches up with your planned dimensions and this could present a problem. I could be wrong but I would be willing to bet the plan is sized at 10’ X 10’ X 14’ on the long side. The top grid looks like 2 X 6’s the long hypotenuse piece looks like 16’ long, 14’ plus 1’ overhang at each end. Sounds lite but the strength comes from the triangulation and it is only supporting itself, no large flat surfaces so wind effects are very low.

The problem with your dimensions is that the hypotenuse would be the square root of 144 + 144 = 16.97 + 2’ for the overhangs = 19’. You would have to go to 2×8’s for the top grid to take the bounce out of it and a 19’er might be hard to source. The heavier grid would change the look a bit from the above picture, if thats ok with you and you can source the heavier material with the few long boards required I think you would be good to go.

Why do I think the one in the picture is smaller, look at the top grid, the cross pieces look like they are on 16” centers which would make the hypotenuse board exactly 16’ long including the overhangs.

-- "There are no utopias, chaos theory reigns, anyone who says different is selling you something"

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