Building a play scape for the kids - questions about hardware

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Old 03-29-18, 04:10 PM
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Building a play scape for the kids - questions about hardware

I'm in the process of designing a play structure for the kids. I know, I know - I can just buy a kit and slap it together, but those are expensive and not what I am wanting. So I am finishing up the CAD model and starting to cost everything out when I came to the hardware. Nuts, bolts, washers... that kind of stuff. All of the major joints are made with dados (the tall brown 4x6s in the picture are notched with the 2x6 nested into them).

Now, since I am using pressure treated lumber, I know that I need to use hot dipped galvanized or stainless steel hardware. That part is easy. Here are where I'm getting hung up:
  1. Carriage bolts - I hate carriage bolts. Once you sink it in, forget about ever getting it back out. Do I have to use carriage bolts? I'd love to countersink some hex heads in, but they are soooo much more expensive. On McMaster, I can get carriage bolts 25 for $9.87, or hex head are 5 for $5.18! Any advice here? Is there a way to get those carriage bolts not to turn when I go to dis assemble this in 10 years?
  2. Size of hardware. I'd love any guidance you guys have here. 1/2", 5/16", 3/8"...?
  3. Grade of bolts. Never really had to deal with this before, but there are different strength ratings for bolts. All the HDG bolts are "Low-strength steel". Someone help me feel good about putting my kids on a playstructure held together with "low-strength steel" bolts.
To give you a sense of scale, the raised platform is 6x12', and the peak of the roof is just shy of 13' high.

thx

PS, this is my first post here, so apologies if I forgot some pertinent info.
 
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Old 03-29-18, 04:28 PM
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1. I would go with carriage bolts. Push them into the hole. Whack the head with a hammer and tighten the nut on the other side and your done. The domed head left on one side is more child friendly laking in sharp corners. Hex heads also work though you have to have a wrench on both ends for tightening and it's slightly more pointy on little heads. Counter sinking is more work and you have the edges of the hole that could make splinters.

2. Size of hardware depends on what you're holding. For major joints of the frame I'd use 1/2". Even if they seriously rust there is a lot of metal for the rust to get through before it affects strength. When attaching accessories like a slide or sun shade I would go smaller.

3. You don't have much choice on grade. You really need to use hot dip galvanized for corrosion protection against the elements and treatment in lumber. Higher grade bolts like 5 and 8 are intended for interior or machinery use. They may be plated but not adequately for outdoor use and especially with pressure treated lumber. Don't worry about the lower grade. Hot dip galvanized are approved by building code for attaching a deck to a house. If you are still concerned about the strength of the lower grade bolts just go up a size. Nothing will provide confidence like a big 5/8" or 3/4" bolt.
 
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Old 03-29-18, 04:33 PM
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As they say, stainless is forever, but the cost is high and the chance you will ever reuse is slim!

1/2 is a good size, keep it consistent!
 
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Old 03-30-18, 09:12 AM
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Awesome - thanks for the detailed answers.

I am getting more comfortable with carriage bolts as I've found a couple solutions to square shoulder reaming out the wood. One solution was to insert a small nail or two as 'shims' as you put the bolt in. The other is this Carriage Secure metal insert made by JordanBolts. It's more cost, is the sort of thing I was expecting to find more widespread.
https://www.amazon.com/Carriage-Surf.../dp/B06XF8JXVN
 
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Old 03-30-18, 10:24 AM
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Yeah, biggest concern with the carriage bolts is getting them tightened initially, and then snugging them us as the wood dries. Most likely if and when we move, the playscape would stay with the house. Moving it is unlikely, but needing to tighten, modify, or repair is much more likely.
 
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Old 03-30-18, 10:26 AM
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You will have the same problem regardless of the bolts you choose. It's the downside of building with wood.
 
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