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I plan to build a floating desk with the following dimensions: 75"-79" long and 22"-24" deep. I plan to mount it to concrete wall(see Image). My Preferred material is MDF.

enter image description here

The desk intended for use as computer desk and writing-reading desk. The load on the desk will be mainly consists of: monitor screen, books, laptop and so on.

My goal is to create a strong and stable desk that can support not only the load described above, but also beyond that(specifically: adult leaning on the desk with his arms).

My question is: How can I support the desk without any legs or bracket?

EDIT: There is a similar question to my question on the site(HERE) but I think the solution proposed does not fit my question. Since to my opinion the proposed support in solution is too weak for my purposes. I'm pretty sure that if I will lean down on the edge of the desk with time not only it will created a 'belly' but it will damage the Alum angle stability (maximum torque). I think the proposed solution is better suited for shelf that functions as a desk, and I want a strong desk that can support for example a person sitting over it.

Note: I do not care if the most of the entire thickness of the desk(based on the design offered) would be a hollow, as long as it's does not exceed 5''.

  • This thing is huge. Use 5" solid MDF? – Mazura Sep 23 '14 at 6:08
  • No. In the size mentioned I took into account that apart from the thickness of the top of the desk(lest say one of you proposed an 1") there will be an additional thickness from the support(let say 3"). In other words, By 5" I mean the total thickness(top+bottom+support) that is accepted on me. – Shmuel Sep 23 '14 at 6:46
  • It brought to mind how mount it from only side. First, it must not deflect at all hence the thickness. Also being that thick it will support itself when cored from the under-side (to create space to tighten the nuts) and drilled from the back side to accept threaded rod you have fastened into the concrete. I'd use giant bolts and as big a slab of real wood as I could get. I can't think of a way to meet your 'sit on it' requirement without it not being constructed out of MDF. – Mazura Sep 23 '14 at 8:09
  • You can add some other material to the structure like hardwood. – Shmuel Sep 23 '14 at 8:24
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    If you don't want legs, and don't want any visible brackets/braces, then this is a serious engineering problem and I don't think there's going to be an easy answer short of running a guy wire to the ceiling... which I presume is also unacceptable. You're potentially dealing with a lot of lever-arm there, even if the three corners at the walls are well secured. – keshlam Sep 23 '14 at 12:58
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This is a pretty standard construction for floating shelves/counter top.

  1. enter image description here mount a cleat to the walls (the third wall is omitted for clarity sake). In this example it's a 1x4 but that will depend on how much weight it needs to bear.
  2. enter image description here Create a torsion box leaving a socket around the edges to accept the cleat.
  3. List item mount the unit and apply a backsplash to cover the gap where the back and sides meet the wall. It's not impossible to scribe in a three sided surface but it's a tremendous pain in the neck.

I would recommend MDO over MDF as it has the strength to weight ratio of plywood but the surface of mdf. As for the thickness w.r.t the strength of the front edge... this is really pushing the limit of what you can support without a leg or integral steal beam and not experience serious deflection or failure.

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You are essentially asking for a floating shelf--albeit a really large one.

This means all the support has to be hidden in a wall. Since you have a concrete wall, you're going to have to build out a new wall in front.

A technique to borrow is how floating stairs are built. A steel support structure is embedded inside the stud wall. The treads then attach to the steel support structure.

You'd have to do the same. One option would be to stud out a wall in front of the concrete then attach large steel T-brackets to the studs (so that the stem of the T sticks out). You'd then build the desk around the exposed stems of the brackets.

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    Thanks for the response. I did not understand why I have to build a wall before the concrete wall? Why not attach the T bracket directly into the concrete wall and after that build the desk around? its can be hidden. – Shmuel Sep 23 '14 at 16:43
  • Yes, it can be hidden...a wall is typically the easiest way to hide it. You could possibly attach a t-bracket to the existing concrete, but that would potentially be more difficult than just building out a stud wall in the first place. – DA01 Sep 23 '14 at 16:44
  • I prefer not to build another wall. Can you give more details about what you suggested: dimension of the brackets, there thickness, load capacity, their distribution along the width of the desk. – Shmuel Sep 23 '14 at 17:01
  • I'm not an engineer so would likely overbuild. I'd use t-brackets 16" OC (to match the stud wall). Maybe 1/8" steel with 18" stems. – DA01 Sep 23 '14 at 17:05
  • I got it. Can you upload a picture of t-bracket so that i know for sure what to buy? – Shmuel Sep 23 '14 at 17:27

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