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Thread: Platform Bed Design Critique

  1. #1
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    Platform Bed Design Critique

    Soo...I'm not even halfway through my coffee table project when an opportunity comes up to build a platform bed for a friend. So after a little research and a few back and forth exchanges with the owner-to-be, I've come up with a simple and traditional design for a king size bed frame that may or may not be used with tatami mats (actually, the owner-to-be doesn't even know whether they will get a futon or a regular coil type mattress).

    The style and material were selected by the owner-to-be, so there isn't too much room for change there. Mostly I'm concerned about the load-bearing capabilities of the wood at the current dimensions, and whether there's a better durable clear finish than polyurethane for this application.

    Since I've never built a bed like this before (or any other style for that matter), I would welcome any sage advice, particularly in the following areas:

    • thickness of the rails, for both strength and aesthetic appeal
    • choice of wood: possible pitfalls/caveats for milling and finishing
    • height from floor to top of frame


    platformBed_01.png platformBed_02.png
    platformBed-post_01.png

    Here are the design basics:

    Overall dimensions: 82" x 85" x 8" H (may go to a 10 or 12" height)
    Internal dimension (area for mattress): 76" x 80" x 2" H (tatami mats are typically 2")
    Frame and post material (including center support: Ash, white, prime
    Mattress slats/supports material: poplar, 3/4" x 2 1/2" x length
    Rails: 5" x 1 1/4"
    Corner posts: 4 3/4" x 4 3/4" x8" H
    Finish: seal coat (not sure of product yet) and clear matte oil-based polyurethane
    Last edited by Mike Ontko; 05-18-2015 at 10:16 PM.

  2. #2
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    Assuming the legs on the center rail hit the floor........

    For as dead load, that seems OK. However, for an - ahem - live load on the bed the 40" +/- span for 1 x 3 slats might not keep "active" owners from an unexpected interruption. If I might suggest - put two more of those supports in the midspan of the 40" slats.
    When I started woodworking, I didn't know squat. I have progressed in 30 years - now I do know squat.

  3. #3
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    Kent, thanks for your input. You're recommending a total of 3 supporting braces then, spaced evenly across the width?

    like so?

    platformBed_03.png
    Last edited by Mike Ontko; 05-18-2015 at 10:25 PM.

  4. #4
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    Quote Originally Posted by Mike Ontko View Post
    Kent, thanks for your input. You're recommending a total of 3 supporting braces then, spaced evenly across the width?
    Yep - you have one running down the centerline - add one on each side, in midspan. The 1x3 slats will be supported every 20" or so...........

    That's my off-the-cuff analysis, anyhoo. Wait for the talent to show up with their thoughts.
    When I started woodworking, I didn't know squat. I have progressed in 30 years - now I do know squat.

  5. #5
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    The usual understructure for a slatted king bed is one rail on the mid-line of the bed, and one leg on it in the middle. Your first drawing has one more leg, so it should be good. A single 1x3 40" long would be at risk if it were supporting the entire weight of the sleeper. However, the sleeper's weight is distributed across many of those slats. The slats are expected to be a little springy, to provide a little give under the sleeper. Running a rail directly under the sleeper takes away that springiness. That is, I'd go back to the original drawing, except that I'd make the midline rail as tall as the side rails. After all, that midline rail is supporting half the weight of both sleepers.

    I only know about American mattresses. Are you saying that Japanese sleep on a single layer of tatami mat that is only 2" thick?

  6. #6
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    I'm basing my understanding off of online research...and hoping that my sources were at least somewhat reputable

    The tatami mat functions something like a mattress box spring, and sits on top of the bed frame much in the same way that tatami floor mats would have been placed across the open frame of the floor in a traditional built house. The mats provide a firm support that allows air flow beneath the mattress, or shikibuton. If this bed were to include the tatami mats, their tops would sit flush with the top of the frame rails, creating that platform "look" that this bed style is known for.

    Back to a single support rail at the halfway point between both sets of slats:

    platformBed_04.png
    Last edited by Mike Ontko; 05-19-2015 at 12:15 AM.

  7. #7
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    Quote Originally Posted by Mike Ontko View Post
    ..

    Back to a single support rail at the halfway point between both sets of slats:

    platformBed_04.png
    Yeah, but that middle rail should be taller and maybe wider too. It supports the half the weight of both sleepers, whereas the outer rails only get half the weight of one sleeper.

  8. #8
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    Quote Originally Posted by Jamie Buxton View Post
    Yeah, but that middle rail should be taller and maybe wider too. It supports the half the weight of both sleepers, whereas the outer rails only get half the weight of one sleeper.
    The middle rail can't be any taller than it is otherwise there'd be a noticeable hump running down the middle of the bed

    The middle rail sits in half lap joints, flush with the support pieces that the slats sit on top of. I could make the supporting legs fatter and the middle rail thicker than 3/4" and wider than the 2" I've drawn. Or, possibly just run a third T-shaped rail with two legs?

    Like so:

    platformBed_05.jpg
    Last edited by Mike Ontko; 05-19-2015 at 12:47 AM.

  9. #9
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    Nice design. A word about the mattress, I don't know about the Tatami type in this case. True, a standard nominal eastern King is 76 X80. Fact is mattress manufacturers are +/-1" across the spectrum. Because of this it is a good idea to have the mattress on hand to measure. Might also consider the lady that makes the bed and any possible ring on a finger between the mattress and the rail. That and bedding makes an over size cavity for the mattress a good thing. A one or two inch greater length and width are good if space allows. Your design looks good and should support a dynamic load to satisfy the total of the occupants and the mattress.
    Last edited by Fred Heenie; 05-19-2015 at 6:53 AM.

  10. #10
    We have a queen size bed of that basic design made of koa (my wife bought it in Hawaii) with tatami mats. She originally used it with a futon but we now have a regular mattress on it.

    The legs and rails are joined in the same way as you've drawn it. The central rail runs the length of the bed (with a single leg in the middle) and it is flush with the cleats on the inside of the side rails. There are slats running crosswise sitting on the cleats and central rail. Two slats end to end meeting at the central rail. These slats are attached together with web straps and sit over short pieces of dowel to keep them from shifting. It all knocks down without tools and is very stable.

    You might want to see if you can get your client to commit in a decision about the tatami mats. The height of the bed will be different with or without them and that height might be important to her.

    Fortunately, with this style of bed, there's no place for a finger to get trapped between mattress and rail.





    Last edited by Dave Richards; 05-19-2015 at 7:08 AM.

  11. #11
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    Dave,

    Thanks for the pictures and explanation! It's funny how little detail there is on the Internet regarding this type of bed design (or, maybe it's such a simple design concept that there's no need?).

    Tieing the slats together with nylon strap is something that I was planning on doing, so that it'll be easy to assemble and keep everything together during breakdowns and moves. Dowel pins as locators for the slats will work as well.

    Even as a queen-size bed, I'll bet that koa makes it weigh a ton!

    Oh...and thanks again for your tips (and instructional video) on using SU!! As you can tell from the earlier posts, I'm beginning to get the hang of things.

  12. #12
    Mike,

    Glad to help, both with the pictures and SketchUp. I'm glad to see you are using it and you seem to being doing alright with it.

    You're right. It is a heavy bed. My wife really loved that bed to ship it to Minnesota when she moved back. It must have cost a fortune. That was before I met her so I have no idea. Being able to roll the slats up and the fact they are only as wide as the tatami mats (which are amazingly heavy on their own) certainly makes them easier to handle when the bed needs to be moved.

    By the way, there are only 3 or 4 pegs used along the length for securing the slats. Most of the slats don't have them.

  13. #13
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    Quote Originally Posted by Dave Richards View Post
    By the way, there are only 3 or 4 pegs used along the length for securing the slats. Most of the slats don't have them.
    Dave, Do you have an idea of how thick the rails are? They don't appear to be a full 1 1/2".

  14. #14
    I don't remember but I'll see if I can measure them tonight. You are referring to the cleats on the inside that the slats sit on?

  15. #15
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    Thanks for the pics, Dave. I had no idea the mats were that thick. Had in my mind a single layer, like a beach mat and thought anyone using them was a tough cookie

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