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Builderdash
Jan 21, 2009, 1:14 AM
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Registered: Jan 15, 2009
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Okay, so i'm plotting on a bouldering cave in my attic. House is fairly old (1950's) In the attic the joists are 2" x 6"s / 16 inches apart center to center. Now, i live with 2 engineers. I am in school for engineering and am no slouch. So they think it is necessary to put 4" x 4" blocks inbetween the joists to attach the plywood for the bouldering wall to. Another friend with a degree in, you guessed it, engineering and I believe the joists are plenty strong enough by themselves to hold the plywood and a person weight. Our reasoning is this: There is plywood on the other side of the joists that forms the roof. If you attach more plywood on the interior side of the joists then it doesn't matter where or how you apply force to a hold, the entire piece of plywood and every joist in the ceiling that piece is attached to will bear the force distributed across the whole. And, we maintain that no force created by someone of human and climbing weight could possibly create enough force to cause damage to the structure, with or without the added 4" x 4" blocks bracing inbetween the joists. Now the question. Theoretical engineering aside, does anyone have any "actual experience" pertinent to a situation like this that could settle this disagreement between my friends and i? Thanks for hanging in there.
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rockforlife
Jan 21, 2009, 1:25 AM
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Registered: May 14, 2002
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With the walls i have helped build we have not put them in. Unless it was a tall wall, so it depends on how tall you are going. But I would say in an attic with the roof on the other side you will be just fine.
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wrbill
Jan 21, 2009, 1:58 AM
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I understand your concerns, but I will make it simple. From what I have seen engineers, with a degree or still in school will over think what it is that they are trying to do when it is simple. I am not trying to put you down in any way, just telling it like I see it. You may have heard the old saying "KISS" (Keep It Simple Stupid). Again not saying that you are stupid, but the simple way is all most always the best way. As for what you want to do I would say you are just fine and will have no problems. Look at the pics of my wall on my profile. You will see that the wall is attached to the ceiling joist with no added support. My wall was built using 2X4's, screws and some lag bolts. The lag bolts are what I used to attach the 2X4's to the ceiling joist. Any have fun building you wall and climbing when it is done. Plus if you have any question just ask and I will see if I can help.
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Builderdash
Jan 21, 2009, 2:46 AM
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Registered: Jan 15, 2009
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Thanks for the responses guys. Bill, keeping it simple was definitely my plan from the start, it seems the minute an engineer gets involved in anything it gets overworked from my experience, but i live with the guys so i have to ease their concerns and issues so that i can get on with my project and get hanging. I forgot to mention in the original post, but since i'm in the attic the joists come up to form a V and then there are horizontal boards connected between the joists creating a roof to the "cave" I'm just gonna pump 3" wood screws into the plywood and the joists and off i go. It was like it was set up with a boulder cave in mind... Anyway, i'll get some pics together as it takes shape and keep you appraised of progress. Thanks again peeps.
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dynosore
Jan 21, 2009, 3:11 AM
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Builderdash wrote: Now, i live with 2 engineers. I am in school for engineering and am no slouch. So they think it is necessary to put 4" x 4" blocks inbetween the joists to attach the plywood for the bouldering wall to. I take it your engineer friends haven't done much carpentry. My 2x6 wall with treated 3/4" plywood has been outside continuously for 4+ years in rotten Michigan weather and it's bombproof. The frame is on 12" centers, but I could have easily gone with 16".
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bennydh
Jan 21, 2009, 4:07 AM
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There is the option of sistering the 2x6 with 6 inch ply strips, and then attaching plywood as you would anyway over the 2x6's. It's not as bulky as the 4x4 option, and its still very strong. This is good practice when notching framing for a pipe or electrical. It probably works here.
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granite_grrl
Jan 21, 2009, 12:39 PM
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Registered: Oct 25, 2002
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It sounds like the OP needs to get rid of those engineers and pull in some carpenters.
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yodadave
Jan 21, 2009, 1:03 PM
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ok kids, its story time with Dave the Carpenter. So presumably your attic has a roof on the other side of it? Yes....... good. This means that your not getting wet right now. Anyway ..... On the roof is probably something other than plywood, Yes.......... Good. Its probably, shingles, slate, tiles or metal roofing. IF this is all true so far then please ask your engineer friends how on earth the shingles managed to get on your roof and attach themselves without a human. Thus if someone can stand on your roof then you can hang from your roof. Your applying the exact same kind of load. Also if you are gonna block to rafter spaces use 2*4 material. There is no need for 4*4. You'll probably need to do this anywhere there is a plywood joint. Also you may want to consider slapping up some insulation behind the plywood so you can boulder for more of the year comfortably.
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bozher
Jan 21, 2009, 1:06 PM
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Roofs are plenty strong enough to walk on, or even jump onto. Why wouldn't it be strong enough to hang on the underside of one? It would be the same force wouldn't it?
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rat-baby
Jan 21, 2009, 1:42 PM
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Registered: Jul 17, 2002
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wow! engineers? wow! Simple load problems. Wow.
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