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Cantilevered Bunk Beds

netniks's picture

I am planning bunk beds which do not extend to the floor, but, instead, are supported by brackets fastened to the wall. Calling them cantilevered may be incorrect. Hopefully, the image that I have included says it all.

Now, the part that I do not know how to "engineer" is proper load bearing. Three brackets should be enough (I think) for a twin size bed. Where would one go in order to find out how to properly size the brackets?

Thanks and regards,

Todd

 "remember what fun we had when we were little,... running, jumping, and eating the raisins off of flypaper?" 

The brackets will not only (post #198372, reply #1 of 15)

The brackets will not only have to support the total vertical load of the "inhabitants", but also the maximum torque generated when there are point loads near the unsupported end of the bed -- not to mention any dynamic loads.

For example assume a 100# occupant sitting at a point 6 ft from the attached end of the bed. The brackets and structure then must resist a 600 ftt-lb torque effectively applied right at the junction of the wall & the bed rail. If that occupant likes to bounce around a little bit, the loads will be a lot higher.

For Children, but still... (post #198372, reply #2 of 15)

Thanks for your comment bd! You provided the kind of structural insight that I desperately need.

I don't know if this image changes some of the load concerns, but I was thinking about reinforcing the plane of the wall with slats. In my mind, the brackets are only as strong as the 2x4 wall partitions + the multiple instances of 1x3's. I'm pretty sure that I could over-engineer the supports,... but you know that I'm not working from a place of knowledge about the real stresses a "bunk bed" like this would truly need.

 "remember what fun we had when we were little,... running, jumping, and eating the raisins off of flypaper?" 

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The brackets will be a (post #198372, reply #3 of 15)

The brackets will be a significant hazard to the occupant below.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Two boys, both want top bunk (post #198372, reply #4 of 15)

Thanks DanH!

In hindsight, I probably should have referred to the bed(s) as loft beds. I have two boys who both want the top bunk, soooooo,.... I'm in need of structural advice for how to properly build safe and attractive bunk/loft/cantilevered/bracketed beds on either side of a bedroom. Where does one go to obtain this kind of help? If it is simpler to just over-build, then I can go that route. I'm not using metal, but these do what is required and hold an amazing amount of weight:

 "remember what fun we had when we were little,... running, jumping, and eating the raisins off of flypaper?" 

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Maybe you should be using (post #198372, reply #5 of 15)

Maybe you should be using metal.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Think about it.  The (post #198372, reply #6 of 15)

Think about it.  The difficulty is not in making knee-braced brackets that are strong enough -- properly constructed they can withstand an enormous amount of force.  Rather, the problem is at the connections to the wall and bedframe.

If you mount a 4-foot-wide bed on a bracket that describes a 2-foot triangle, then sit a 200 lb person on the edge of the bed, there will be 400 pounds pulling out at the top of the bracket and 400 pounds pushing in at the bottom.  Not only is it difficult to achieve anchorage able to withstand the pull-out force, but you also have substantial tendency to actually deform the wall.  Yes, it helps somewhat to spread the load among several brackets, but someone sitting near one end will concentrate most of the force on one bracket.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Good Input (post #198372, reply #7 of 15)

Thanks again DanH. You're giving me some good ideas. So as to provide better support, what if I secured one end to the adjoining wall, so that there is support along one long side and one short side, *and* support the other short end with a ladder? I don't see how I would max out the tensile strength of even a 2x4, but I can certainly see what you're saying about the connections *to* the 2x4's. Also, I accepted that the bed-wall-bracket would describe a 4-foot triangle, creating a substantial "foot" for the diagonal brace.

 "remember what fun we had when we were little,... running, jumping, and eating the raisins off of flypaper?" 

it can definitely be done (post #198372, reply #8 of 15)

but you need a total solution because of the likely occurrence of concentrated loads as Dan pointed out. Not only do you need to worry about the brackets and wall attachment, but the wall structure itself.

If you're willing to put forth the effort to construct the beds properly, I'd suggest seeing a local engineer. It shouldn't cost too much to get some detailed design help on something like that. If you're lucky, you might find someone that'd do it just for grins or a minimal fee since it would most likely not require a PE's stamp. A lot easier to sit and talk about it over a cup of coffee & flesh out the details, e.g., how big are the kids? how long are you planning on using? etc. With a little design help, it'd probably be possible to fabricate some metal brackets that would support the beds and also provide adequate bracing to the wall structure.

One important point:  The (post #198372, reply #9 of 15)

One important point:  The kids will get older, and they will have friends over (maybe some who are a bit overweight).  Just because the kids are under 100 pounds right now doesn't prevent there from being a 500 pound load at some time in the future.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

of course (post #198372, reply #10 of 15)

of course

Thanks for the comments (post #198372, reply #11 of 15)

I know a lot of home building and remodeling involves ensuring that a structure is supported all the way down to the foundation, so I appreciate the cautionary comments. They're meant out of concern for safety, and that's not lost on me.

Honestly, I didn't even know that structural engineering was its own discipline. Just from observation, however, I've seen closet shelves supported by simple brackets carry *a lot* of weight. I've seen them collapse, too, so I want adequately built bed bracket supports.

I do want the supports to look like furniture, and not necessarily something fabricated for a factory. I'll definitely consult a structural engineer, however. I often ask myself, "what would MacGyver do?",… but I'm pretty sure even he couldn't pull this off with just a paper clip and duct tape.

 "remember what fun we had when we were little,... running, jumping, and eating the raisins off of flypaper?" 

Is this really a good idea? (post #198372, reply #12 of 15)

I often tell the DW that just because something sounds like a good idea, that does not mean that it will actually work. I can't help but wonder if your bed design is an example of this.

I was at Talesign (sp?), Frank Lloyd Wright's Wisconsin home, where he had a cantilevered balcony. They found that when a one person walked to the far end of the cantilever, the base of the cantilever moved over a foot! The other posters are not kidding when they talk about the actual load created and the possibilty of bowing a wall.

Good luck.

 

"lofty" ideas (post #198372, reply #13 of 15)

It's funny how I thought of FLW's cantilevered inventions, especially the piano "hidden" inside a stairway at his home and studio in Oak Park, IL and the generous platforms of House on Fallingwater when envisioning my loft beds.

Ideally, I would sister a metal beam beside a 2x4, and secure it to the header and footer of the wall, and bolt the brackets to the beams. I haven't decided how much I want to tear into the walls before I just go with two conventional platform beds for the kids.

I don't think I'm even talking about a cantilever anymore if I secure the foot of the bed to the adjacent wall of the long side, and then support the other short side with a ladder.

 "remember what fun we had when we were little,... running, jumping, and eating the raisins off of flypaper?" 

Reference images (post #198372, reply #14 of 15)

These two photos show a little bit of what I am trying to accomplish, albeit as free-standing units. The first image appears to show a support cord extending up to the ceiling, and may simply be representative of a "suspended" bed.

The second image appears to be metal, but the supports are very simple. An unattractive solution to my eyes, but still...

 "remember what fun we had when we were little,... running, jumping, and eating the raisins off of flypaper?" 

  I know this is a little (post #198372, reply #15 of 15)

 

I know this is a little late but I've used the method shown in the attached picture for metal and lumber storage and loaded them with way over a 1000 lbs. This way you are not putting as much of a load on only a few fasteners.

It could be dressed up to look architectural in my opinion. 

if you used 4 vertical supports you may not need any diagonal bracing at all. 

Best regards

Tyler Smutz

www.killstressdesigns.com

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