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  1. #1
    Senior Member RAW's Avatar
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    Hanging indoors: concrete-specific questions

    Howdy, y'all. Long time, no talk! My kiddos keep me too busy for much hammock camping these days. Hopefully as they get older, I can get them to hang in the woods, too.

    Getting to my questions . . .

    My wife and I want to replace our bed with a small couch for daytime use and hammocks for nighttime.

    Outside wall is a sandwich of 4" concrete--2 polystyrene--4" concrete. The wythes of concrete are tied to the insulation layer by special, plastic form-ties.
    The opposite wall is 17 ft. away. It is an interior wall that is 6" concrete.

    I weigh 260#, but let's figure 300# for each hammock to build in a lot of extra safety margin. I plan to fabricate the anchors from steel plate, with 4 bolts in each (1 per corner). Unless someone has a better idea or thinks this is overkill. But how large should each base plate be? And what size bolts? Wedge anchors or something else?

    For the two hammocks, how far apart should the anchors be on each wall to allow for slight rocking without bumping into one another?

    Any other thoughts? I know there are a bunch of clever folks here..

  2. #2
    Senior Member Mouseskowitz's Avatar
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    Sounds like an interesting project!!! Wish I knew more about this style of construction and what type of lateral strength it has. Is there any type of rebar in either of the walls? I'm also wondering why this vs a stand?

  3. #3
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    Just to be clear, are the interior and exterior walls poured concrete, or concrete blocks?

    Is the interior wall bearing or non-bearing (carrying a load or just a divider)?

    Wedge or expansion anchors should have the pull out strengths labeled.

  4. #4
    Member jmoffatt's Avatar
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    that house must be hurricane proof

  5. #5
    Detail Man's Avatar
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    I did a quick search and found this website that has LOTS of info on all the different anchor types: http://www.confast.com/concrete-fasteners.aspx This is a vendor, but they certainly believe in educating their buyers. Personally I'd probably go with wedge anchors. Spacing is a function of anchor diameter.

  6. #6
    Senior Member RAW's Avatar
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    I would like to avoid stands because I want the floor space clear when we're not sleeping.

    The walls are poured concrete. Each wythe has an embedded rebar grid.
    As for the load-bearing: each wall has z-purlins that run across the tops of the walls, holding the metal roof panels.

    I lean towards the wedge anchors, too (probably just cuz I've used them before). But according to the hammock hang calculator, I could get away with tapcons. Perhaps it would be sufficient to do a vertical, rectangular plate with just two wedge anchors.

    My spacing question was more about hammock spacing. I've always hung solo. So I'm not sure how far apart I should put the two hammocks to avoid bumping into each other.

  7. #7
    Senior Member Mouseskowitz's Avatar
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    That's an educational site. I'm no engineer but I have two thoughts. First, if you wanted to go with the plate idea a 14 in plate with 3/8 in wedge anchors 3 in deep would over 3000 lb per bolt, not sure if you get to multiply by 4 or not. Second, it would look like you could go with something like a 3/4 in wedge anchor at 8 in to tap into the second layer of concrete on one side and 5 in on the other. That would give you about 10,000 lb and then thread an eye nut like this on the end, providing the threading is compatible.

    On second thought that's probably way to over engineered. If my amsteel suspension is good at 1600 lb anchors in that neighborhood should be good too. 1/2 x 4 in wedge anchors with the lifting eye nut would be limited to the 2150 lb strength of the eye nut. That would give you an almost 10:1 safety ratio.
    Last edited by Mouseskowitz; 01-13-2013 at 22:05.

  8. #8

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    I've been using 4"x4" plates with tapcon screws in each corner for the past year+ and my 230ish hasn't had any ill effects, either on the wall or my butt. I don't usually sleep in it but I'm probably in it at least an hour a day.

    I used something like this but after the cheap weld on the ring split I replaced the ring with a quicklink.
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    Last edited by keg; 01-13-2013 at 22:03.

  9. #9
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    A 1/2" wedge anchor with a 1/2" I bolt would hold you with no problem if set properly. I think a 4" plate with four 3/8" anchors (shells) would be your safest bet. You never know what you hit or being your first time, how well you set them. I also am not sure of the concrete. Make sure you don't drill too deep that the anchor get hammered into the center void. They do sell "shallow" anchors at Home Depot that could be used in this situation. I would definitely not use tapcons. They can strip out or even loosen up.
    As for distances apart, not really sure. Give yourself enough height so you can adjust tensions and foot rise without being too high or too low. That could be the tougher part.

  10. #10
    Detail Man's Avatar
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    When hanging tandem, I use 26" spreader bars on the hammocks. It's enough to keep both rigs under one tarp, but occassional contact happens. 36" might be better for a permanent setup. You could each take turns in a hammock and measure the max space (width) you occupy while lying in various positions. The spacing would be the largest measurement + a few inches. If wall space allows, instead of hanging exactly parallel, you could position the head ends a little closer together to allow for good morning kisses form the hammock .

    A particular anchor may spec out at needing just one or two anchors, but what will give you peace of mind each night in the long term? None of these fasteners/plates are very expensive. If you've got a proper hammer drill (bits with SDS Plus shanks) setting anchors is easy.

    Another option instead of a plate and ring is to mount a piece of slotted angle to the wall vertically. This will allow you to adjust the hang angle/hammock height more easily. Attached is a pic of what I did in my daughter's room.
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