How to mount posts for pergola with swings

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Old 03-26-17, 03:25 PM
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How to mount posts for pergola with swings

I am in the planning phase for a 12x16 pergola. 6x6 posts, 2x10 double beams the long way, 2x6 rafters the short way. Havent decided on battens yet, but if I do them, it will be 1x2. All PT lumber. Angle bracing at all four posts in both directions. Posts notched and beams resting in the notch, then through bolts. Possibly hurricane ties to attach the rafters, unless I decide to notch all of them.
Heres where I come to my question. My plan would normally be to make concrete footers and use post base brackets to attach the posts to the footers. But given the fact that this pergola was the product of a negotiation with my little girls (I told them Id put a hot tub under the pergola and swings on one of the pergola beams as long as I DIDNT have to build them a play house!), I started researching setting posts for pergolas with SWINGS specifically. In no instance do any resources I found online have the posts set in brackets. They all buried their posts in concrete. I dont know if this was a coincidence or if there was a reason to do the posts buried in concrete. I know for most instances people who know better would recommend footers and post base brackets instead of burying in concrete. Do I actually need to bury posts in concrete if I am going to attach swings? Or were all of these examples I found online just coincidentally all misleading? The swings wont be the typical go-high-in-the-sky type most likely just some hanging papasans more for just drifting and relaxing, but Id be shocked if their intended use didnt get stretched a bit.
Your help will be much appreciated!
 
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Old 03-27-17, 04:05 AM
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They all buried their posts in concrete
It comes from not knowing the proper way to do things. Any wood in the ground will have a short life. Shorter than mounting them properly on post bases on footings. Even with all the cross bracing, the pergola will remain stable unless the kids decide to hook a truck to it and try to pull it over.
 
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Old 03-27-17, 06:10 AM
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A swing set is 'A frame' to prevent it tipping over yes. If you don't want to make the pergola 'A frame' and look tacky, then yes bury the 6x6s in concrete. the worst thing you could do is leave the top of the concrete ground level creating a puddle around the posts. Where wood rots the most is where moisture mixes with air and warmth. That's why fence posts crack at the base and then when you dig the posts out, the underground portion where there isn't much air (but could still be plenty of moisture underground), that portion is usually fine. That's why they sell 4x4 fence post 'savers' that are just a 8" sleeve that only goes right at grade level and doesn't sleeve over the entire buried portion of the post (although that's better IMHO).

Anyway, I would get 6x6 fence posts protective sleeves and have the sleeves protrude out the ground a few inches. Some of those sleeves are closed at the bottom, some are open, there are mixed reviews and theories on what lasts the longest. I would go with a closed bottom sleeve with a gasket-type decorative cap ring at the top that you will see a few inches above grade. Some brands don't have that ring cap, instead they rely on allowing water to run all the way down and out the bottom of the sleeve which is another debate if there's enough air down there to rot the bottom or not. You should use the gasket type clap ring cap vs caulk, because a caulk joint will break (with wind for a fence or a swing in your case, plus wind), but a rubber gasket (you won't see the rubber part) should remain tight and sealed.
 
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Old 03-27-17, 08:49 AM
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Oh, no... two contradictory opinions! I'd like to hear from some tiebreakers! I'm attaching a picture I finally found this morning in which post brackets are evident. Now this is a very different structure than the rectangular one I am planning, but it still features swings hung from the beams at the side, rather than from the center of the structure. The fact that they are counter-balanced by swings on the opposite sides is something I would discredit by saying that one can never guarantee that someone will always be sitting and swinging opposite another person swinging... so I can therefore guess that swings on a single side are therefore ok. But I'd still like to hear more from you all. I've also seen several examples of swings hung from two-post arbor structures in a single plane, so...

I'm not partial to either method but just want to make sure I'm doing this right. Thanks much.
 
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Old 03-27-17, 04:16 PM
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Too many "ifs" in Gunner's theory. Note the poured footers in the example you show? That is the way to do it. You have already stated it is not a playground swingset, so that point is moot. With heavy angle bracing of the top members it will be like a rock, and a little less expensive than the metal they used.

More of the guys will chime in with their ideas, so hang in there. I'll stand down.
 
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Old 03-27-17, 04:40 PM
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Here is your tie breaker.....

If adding swings, dig out the old posts and start from scratch. Fairly simple in my opinion, for the cost of a few posts, you will get the safe, solid structure you want. You are trying to repurpose something that was not meant for the desired outcome. Always a disaster waiting to happen. Do it right the first time.
 
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Old 03-27-17, 04:43 PM
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those column base anchors should be fine. I was thinking just base anchors you use for deck posts without upward straps. Still make sure to taper the top of the concrete a bit so it doesn't pool around the wood unless the bracket is built with a hollow stand-off base.

'a swing on each side going simultaneously', I would think would be worse if they were in synch, would probably put more stress on the structure, but even with those brackets I would guess it'd be ok.

I'm not a structural engineer, so I would prefer to over-do things to be safe. I think burying the posts in concrete would be stronger. With the protective sleeves, if the posts ever did rot out, you can just slide the post out and install a new one (probably would not come out easy though, would probably have to cut the post flush with the top of the sleeve, install a big eye hook and lever it out with a car jack or something).

simpsons warranty info is quite lengthy, and, " (b) Product deterioration or defect due to environmental conditions or inadequate or improper maintenance, "

https://www.strongtie.com/limited-warranties

I mean, maybe 60-100 years the anchors could rust out, but it's different from a deck footing in which you could just temp prop support the deck up and cutoff wheel the rusted anchor out and retro fit a new anchor with banged-in concrete anchors (unless J bolts are being very required) and put a fresh anchor in such a way without the old buried section being in the way of the new anchors).

In other words, even if you're not living there in 100 years, do you think the post brackets could eventually rust out and then someone decide to take the whole thing down instead of making all new footing and vs if there were plastic sleeves and the 6x6s rotted, they could most likely prop the pergola up temp and slide the old 6x6s out and install new 6x6s. Of course this also depends on how long the wood lasts. but if you were to use particular types of wood they might become petrified and basically last for centuries.
 
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Old 03-27-17, 04:46 PM
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I can not edit on ie11. wood doesn't become Petrified Wood apparently over time, it's instead a fossil. So I don't know if the wood itself would even out-live the anchors, so that might moot the whole idea of the buried 6x6 sleeves meaning the posts can be replaced without the problem a buried anchor could pose.
 
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Old 03-27-17, 05:06 PM
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Sorry, did not mean to mislead that anything had begun already. Nothing has been started. Did you think I had buried them and that is what you say should be redone? If so, I have every opportunity to do it right starting from the beginning.
 
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Old 03-28-17, 12:34 AM
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what I meant about redoing it was I meant in 60-100 years or however long the brackets would last before rusting away, to redo the 6x6s would be harder with a concrete stump there and a rusted anchor buried in it vs a hole with a rotted 6x6 in a 6x6 sleeve and just replace the 6x6, thus your structure would stand for longer even if you're not there anymore. BUT the wood would probably rot out in ~80 years anyway so don't even listen to that part.

personally, I'm not a structural engineer but I think burying them is stronger than those anchors but I think the anchors are ok. I think hanging a swing bench from an eye hook is the weakest link actually.
 
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Old 03-28-17, 07:26 AM
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Oh, I was meaning czizzi about saying I needed to dig posts out and start over... nothing has been started yet.
As for gunner, I see what you mean. At the very least, if I proceed with anchors, I'm glad you mentioned sloping the concrete away from the center because I might not have remembered to do that otherwise.
 
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Old 03-28-17, 03:31 PM
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Based on your location, the cement may only be down 2' into the ground. You may be able to wiggle the posts loose and just pull them out cement and all.
 
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Old 03-30-17, 08:43 AM
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I don't have any posts buried yet. Starting from scratch. Thanks for your help. I'm going to go with anchors in footers.
 
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