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I am planning to build floating (bunk) beds in our old walk in wardrobe. I put the "bunk" in brackets because the bottom half of the bunk is actually just a low platform bed sitting on the floor. The real question (and the bit that I do not want to underengineer or get wrong) is how to construct and secure the floating bed. Below is an image of what I envisage, breifly explained, it will be:

  • A single floating loft bed with monkey bars (there will be a safety rail, just have not drawn it)
  • A double bed underneath "sitting" on the floor
  • Secured to 4 walls, but two of those walls do not extend the entire length / width of the bed
  • 2 of the walls are plasterboard with studs, 1 is concrete covered in plasterboard, 1 is plasterboard with studs and a concrete pillar behind it
  • I plan on securing the frame together using pocket screws or dowel-strengthened end grain screws (like this: https://www.youtube.com/watch?v=bW6RumyOCP8)
  • Hardwood will be used for everything except the bed slats (pine or plywood) and monkey bars which will be metal

My key questions are:

  • What (minimum) size planks should I use for the frame (the ones secured to the wall) and joist?
  • Should I put a lag bolt or 2 into every stud / every 40cm in the concrete?
  • Would a joist hanger be sufficent for the middle joist in the frame, or should I use a woodworking joint (e.g. half lap or M&T)
  • I was planning on screwing the inner bed frame to the outer structural frame, however starting to wonder if I should simplify this and add another joist and put the bed slats on the outer structural frame itself
  • Is there anything I haven't considered here, that I should, or that could be improved, design-wise?

Top view

Side angle

Underside

Top side with dimensions

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    I like the design - very clever use of space! Also, very well asked for your first question here. I'd think that simple 2x4 dimensional lumber (or the metric equivalent) would probably be sufficient, however, if you could add some dimensions to the drawings, particularly the first one, so we can see how much is unsupported by direct attachment to a wall, that would help.
    – FreeMan
    Commented Jun 29, 2023 at 21:01
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    For those of us who threw off a king, but cling tightly to his system of measurement... That's 63.5" wide, 93" long, the monkey bars are 24.6" wide. It looks like roughly 1/2 the end span (at the south) is unsupported by a wall, so about 32". The highly accurate "finger calipers" say that the unsupported edge of monkey bar in the northwest corner is roughly 24" as well.
    – FreeMan
    Commented Jun 29, 2023 at 21:18
  • Close! 39" and 14" on the monkey bar overhang at the bottom corner and 30" on the northwest (I did try and get sketchup to convert my measurements to inches, but no dice. It seems to understand logical meausrements ;)
    – Slam
    Commented Jun 29, 2023 at 21:36
  • I'm assuming the monkey bars are for play, and not for access. By my calcs your side rails are 4.5cm. That means you have 41.1 cm (99.2-62.6+4.5) of solid width at the bottom, assuming that's where the access point is. Is that sufficient width? It'll get tiring having to clamber over monkey bars to get in and out of bed. OTOH, you could make a clever flip-up panel that covers the monkey bars when they're not in use.
    – Huesmann
    Commented Jun 30, 2023 at 14:12
  • Ooooo! What a grand idea (the monkey bar platform cover), I think I will try and work that in! Correct, the monley bars are not for access, there will be rope ladder on the south side of the bed (attached to the ceiling)
    – Slam
    Commented Jun 30, 2023 at 15:47

1 Answer 1

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Here is my suggestion. I assume this bed is for one person and roughly supports 250 lbs.

  • I would say 1x4 hardwood is plenty strong. But I would use 1x6 just because it looks more "luxury".
  • Given studs are 16" apart, one 3" screw into each stud is plenty. Use TapCon for the concrete walls. Your bed is attached to 4 walls thus I don't see a risk of it failing. FYI I have a large cabinet in my garage holding my tools and I only used 8 screws to hang it. It must be way over 300 lbs with all my stuff in it.
  • A joist hanger is more than adequate for the middle joist. But you could also do a half-lap or M&T if it bothers you to see the joist hanger when laying on the lower bed.
  • I think eliminating the inner frame would simplify the fabrication. Both options are structurally sound.
  • I noticed your drawings show mitered joints for the outer frame. This kind of joint is not that strong and the outer frame is what holds everything together. If you really want to the miter joint look, I would suggest reenforcing them with a spline, dowels, or use metal L-brackets in the inside of the frame.

Sounds like a fun build. Best of luck.

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