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lossinsantafe
Jul 6, 2004, 10:27 PM
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Registered: Mar 18, 2004
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Hi all.
I'm building a smaller free standing boulder (apprx. 4' W x 6' L, 4' H on one end, 5' on the other). It's basically a framed box (2"x6", mending plates, bolts, screws) with 2x4's making the triangles for interesting angles fixed onto the frame. The base of the frame is ribbed every 16" w/ 2x4, with one 2x6 in dead center, with a carriage bolt in place awaiting some sort of anchoring.
This boulder is going to live at a preschool in Santa Fe, New Mexico where it will live in a play area with 4" deep sand for at least 10 feet in all directions. The perimeter of the area is chain link fenced with poles buried in concrete.
Now just the frame and sheating make up quite a bit of weight, but want to put some kind of anchor into the sand, and fasten the bottom center 2x6 rib into it. Is the best idea here simply to dig a post hole and fix an 6" eye bolt into concrete, then attach via chains? As far as interior access is concerned, the roof sheating will be attached last, so I can climb in and out to work inside until it's anchored.
Thanks for any advice or ideas!
Max
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andy_reagan
Jul 6, 2004, 10:54 PM
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What about just burying the bottom half foot or so under sand. This would effectively stabilize it. Regardless, pictures must be produced upon completion!
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vanclimber
Jul 6, 2004, 11:28 PM
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I'm trying to figure out what you are anchoring it for. If you are anchoring it structurally wouldn't you want a 4x4 post at each corner? If I was building this boulder (and now that you have got me thinking about it I probably will) I would probably start by digging some post holes 12" dia. or so and 3 feet deep on each corner of the boulder. I don't know if I'd pour concrete for something that small...the posts should be strong enough to prevent any shifting. Then after I placed the posts I'd probably fill the bottom 2'6" with gravel or something similar and tamp/vibrate it down firmly. Then build the actual boulder itself 6" below grade (so the lower frame rests on the gravel) and after you have finished sheeting it fill the sand back up to grade.
I'm interested to hear if any structural engineers have other ideas (I'm certainly not a structural engineer, but I frequently have to build to pass structural inspections.)
Don
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chizelz
Jul 7, 2004, 1:35 PM
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Max, I am trying to wrap my head around what you are building there.... I am guessing that its a small boldering venue for kids??? ok that part doesn't matter but I think that the anchoring does..... I'm with Don about the posts, and embedding them into a 'foundation' of sorts. If you simply connect chains to a central pier, I am sure it would be fine for uplift, but what would prevent hooligans from grabbing this thing and spinning it around the central fastening point. The chains would hold it down but wouldn't prevent twisting or turning. Even two posts cemented into the ground would prevent any movement. I don't know anything about the building requirements in New Mexico as far as foundations go, but for example, and maybe it isn't a good one, but for the area of Canada where I live, foundations are required to be a minimum 4'-6" deep to prevent frost 'heave'. Now I am pretty sure that you don't have frost in new Mexico, but your local building official might offer a suggestion for a sturdy foundation. Or........... just follow Dons' advice, and it will be more than sturdy and safe!
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lossinsantafe
Jul 8, 2004, 2:08 PM
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Registered: Mar 18, 2004
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Thanks for the advice, Don- I've decided on going with 4-4x4 posts, each in a concrete tube dug down 3 feet in the sand, first filled with base course for the first foot, then sand. I then moved the base of the frame down a few inches so that the surrounding sand will meet the base about an inch up from the bottom, which should make some some nice sit starts when I'm testing/demoing it for the kids.
Max
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overlord
Jul 9, 2004, 11:36 AM
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Registered: Mar 25, 2002
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make holes, fill with concrete and put anchor in said concrete. make nice big holes.
another way would be to dig a pit, pour a concrete plate on the bottom and put anchoring poles into the plate, covering the whole thing with sand. this should fix it good.
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