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anuvanoob 06-20-2012 02:47 AM

building a floating shelf to support 200 pounds
I have 2 pieces of cut left over plywood that I'd like to use as a floating shelf for a plasma TV, receiver, speakers, etc. Both are 3/4" thick plywood and measure 64" long by 22" wide. The total weight of all the electronics that will sit on it is over 100 pounds, but to be super safe I'd like the shelf to support 200 pounds.

How do construct this floating shelf to support 200 pounds?

JulieMor 06-20-2012 06:13 AM

Sounds like you want to do a torsion box shelf. They can hold a load but I'm not sure for the weight and dimensions you're talking about. The problem comes mostly from extending it 22" out from the wall. You can hang 200 lbs on a stud wall but when 22" out you create a lever that could bring the whole thing down. Google "torsion box shelf load" and maybe you can find something that works.

If I were to tackle something like that I'd open up the wall and install 4x4s where the shelf would be supported. Then I'd install thru bolts and washers (countersunk) to eliminate the wood-screw-threads-ripping-out factor. The shelf would have to be thick enough to distribute the load so as not to bend the thru bolts, probably 6" or more, and require two bolts at each vertical attachment point.

Drywall could crush so I'd consider a hardwood, to attach directly to the 4x4, that would be the same thickness as the drywall. Then I'd pray the whole thing worked.

Of course, you could just put some legs under the shelf and forget re-engineering your wall.

anuvanoob 06-20-2012 01:51 PM

Actually I'm constructing the wall framing now - at the moment I have the top plate screwed in and only the holes drilled for the bottom/sill plate (its being fastened to a concrete basement floor using Tapcon concrete screws/anchors). Also, I'm not using drywall, but reclaimed 3/4" wood floor panels (its going to be an accent wall).

Does that change anything?

JulieMor 06-21-2012 11:17 AM

Yes. For one, you can build the wall specifically to hold the suspended shelf. And you don't have to demo anything and start all over.

Before I make any suggestions, I want you to know I'm not an engineer. I build furniture as a hobby and have learned a lot about wood and strong joints but am by no means any kind of expert. And while I would build it this way, I can't guarantee this will be rock solid. But I would be surprised if it failed.

I drew up some plans the way I would do this and created some cut-away views for clarity. BTW, this would be a pretty permanent installation.
I went with a mortise and tenon joint to connect the horizontal members to the vertical ones. I'm using all 4x4s and would use Douglas fir over construction grade pine. I'd prefer oak lumber but I'd hate hiding it in the wall. Still, the more I think about it, the more I would tend towards the oak. Then I'd figure some way to leave the back of the wall open as an accent feature, such as a wall behind a bar.

The wood you use would have to be seasoned. If you went with oak, that would mean leaving it in your basement for a couple of weeks to acclimate to the humidity.

The mortise and tenon joints wouldn't be all that difficult, even if you've never done it before. There are only three. You could do it all with hand tools but would need a good saw and some decent chisels. You could speed up the process of making the mortise with a drill and a forstner bit. If you don't own any forstner bits, I'd buy one the same diameter as the dowels you intend to use (3/4" in the images).

The reason I show wood dowels instead of screws or bolts is because wood shrinks and swells and metal doesn't (at least not like wood). As wood swells around a bolt or screw, it gets crushed. When the wood shrinks, it creates a looser fit around the bolt or screw.

All the joints have to be very tight and everything would be glued. Glue loses its effectiveness if the joint is loose so take your time and make all the joints snug. Start with the mortise and fit the tenon to match. This is a decent video showing how it could be done just with chisels and a backsaw: I added the dowels for additional strength. All that would require is drilling holes and inserting glued-up dowels, a simple step that would add a lot of strength.
The plywood can be attached with finish nails or clamped with construction adhesive if you don't want to see or fix nail holes. If you're good with a circular saw and have a straight edge, you can cut a 45 degree bevel all around the edges to create the appearance of the shelf being one solid piece. Apply glue to all the edges and finish it off with a wood putty matching the wood tone.

On the back side, I added backer blocks on either side of the horizontal members so you have something to nail the planking to. If you decided to put a bar on the other side, this wall could be used to hold shelves for glasses and such. The backer blocks and additional studs should be the same wood as the 4x4s to give it that finished look. You may be able to find some reclaimed lumber for the wall framing.

If I were to take on this project, that's how I'd do it and I think not only would it hold, but it would look pretty cool. And I'd build the bar too. :yes:

If this seems overwhelming or too time consuming, just think of all the enjoyment you'd get out of it, not to mention bragging rights. :thumbup:

anuvanoob 06-21-2012 12:24 PM

Oh. My. God! That is unbelievably awesome! First off, thanks so much for taking time out of your life to draw this up, very much appreciated!

My skills are very beginner at most but I will try this method anyway. When you say this would be a "permanent installation" does that mean it would be difficult to tear down? I ask because this accent wall and shelf is meant to be a temporary installation since we will be finishing the basement at some point down the road (anywhere between 1 and 3 years hopefully), so it would be ripped out then. I embarked on this whole project to gain some handy man skills, its not pointless building this thing to only tear it down possibly a year later.

Also, I'm fastener this frame to the basement's ceiling joists and concrete floor and in your diagrams the 4x4 are going straight into them and NOT the top or bottom/sill plates? Is that really how I need to attach them or can I go into the plates?

One last thing... worse case scenario that I find it difficult to pull this off, is there another method I can do to support lower weight? Say 60 to 75 pounds (as if I decided to mount the heavy plasma TV on the wall itself)?

JulieMor 06-21-2012 01:11 PM

The attachments between the vertical and horizontal members of the structure are permanent. Once glued together they would have to be cut apart if you wanted to disassemble it.

The wall could be separated at the top and bottom at a later date and be relocated. I wouldn't think of building this just to demo it later. But I would build it if I could relocate it down the road. And if there is a place in your plans that would allow for the back side of the wall to be used as an accent, all the better.

Ignore the 4x4's going to the floor. They are intended to sit on the bottom plate and attach to the bottom of the top plate. If you built it and relocated it later, this would be a good place to detach it (I'd use a sawzall with a metal cutting blade and just cut the screws and nails).

If you want to learn to do mortise and tenon joints, buy some cheap construction lumber and use that to practice. If you looked at the video, you'll see how much force he has to apply to insert the tenon into the mortise. That's what you're looking for.

He has Marples chisels. I bought a set a while back for about $50. That's less than the cost of one of my Lie-Nielsen chisels. They don't hold an edge very well but they will do the job if you keep them sharp. Use a wood mallet or a piece of heavy wood to hammer the chisels.

You could check out a place like Woodcraft, if there's one nearby, and tell them what you're trying to do. They guys there could help you out. They also have workshops. Learning basic wood joints is easy and it could catapult you into a new hobby. That's what happened to me. :laughing:

kwikfishron 06-21-2012 04:18 PM

199 Attachment(s)
I did these shelves floating out of mirror last Winter as part of a bar remodel.

When the wall was opened up I added 4x6 blocking at the shelve locations then ran lags into the wall and cut off the heads.

Drilled out the shelves and slid them over the bolts. I have no doubt they will hold over a hundred pounds.

If you needed to you could remove the lags with vise grips and patch the holes.

This obviously wouldn't work with 3/4" plywood but you get the idea on one way to float shelves.

JulieMor 06-21-2012 06:26 PM

Nice job! How much of the lag screw extended out from the wall before you slid the shelves over them? Is there anything to keep the shelves from pulling out?

Now, could you pour me a Meyer's and Coke with a lime? :biggrin:

robs660 06-21-2012 06:41 PM

I would go another route. I would frame the wall using 4 x 4s. In each one I would drill a hole 1/64" smaller then steel rod. Insert the steel rod all the way into the hole and epoxy it in place. Build your torsion box shelve and use the attached steel dowels as your support. The hardest part of the whole thing is drilling all the holes perfectly. I would drill them on a drill press after per cutting and laying out the studs. I have hung over 300lbs using 1" steel bar. I will sketch this for you and post the sketch as well.
BtW. If you did not epoxy in the steel you could pull them out when you are done and plug the holes

kwikfishron 06-21-2012 07:15 PM

199 Attachment(s)

Originally Posted by JulieMor (Post 948613)
Nice job! How much of the lag screw extended out from the wall before you slid the shelves over them? Is there anything to keep the shelves from pulling out?

There 10” lags so they stuck out about 6 ” for a 10 - 11 ” shelf. The shelf depth varied do to the planned uneven edge.

I had planned on a few hidden trim screws to keep the shelves in place but it turned out they were not needed.

I drilled 5/8” holes for the ” lags and ended up beating them up a few degrees so after the weight of the product was there they ended up level. It took a couple of adjustments but after that I realized that even without the screws they weren’t going anywhere.

The Mirror Guy after drilling out for the lags didn’t leave me as much room for the hidden screws as I was hoping for so I didn’t take a chance.

McCumber12 06-22-2012 03:34 AM


Thanks for your post.

anuvanoob 06-22-2012 04:58 AM

ummm... I'm a little confused now, but I'll try to stick with post #4

woody4249 06-23-2012 06:45 PM

All for a simple life
I'd tackle this the simplest way I know how. We used to build torsion counter tops as ADA access points at nurse stations. They were up to 26" deep and would carry 300lbs easily. They had to be barrier free.
Remove a section of sheetrock where the brackets are to be placed, install what we called a Gambus bracket on each stud at max 24" centers
Go to
If you look at this webpage you can see the construction of the bracket. Install the brackets at the side and behind the stud drilling new holes in the vertical face of the bracket for the lag bolts to hold this to the stud. The fact that the bracket hooks behind the stud makes it even stronger. and allows the bracket vertical to be concealed inside the drywall.
Construct the shelf sufficient in height to slide over the brackets with a removable base or soffet.
Re install the sheetrock you removed, finish and paint.
Prepaint the shelf
Slide the shelf over the brackets and anchor to the shelf underface and install the soffet to conceal the brackets.

anuvanoob 06-25-2012 04:20 AM

Well, what about building this support 75 pounds instead of 200 pounds?

woody4249 06-25-2012 07:49 AM

You can do this without removing the drywall.

Locate your vertical wall studs.
Find the precise center of each one.
Cut sufficient pieces of 3/4" dia galvanized pipe to approx shelf depth length.
Bore a hole at 90 tightly match pipe dia into the stud at shelf height.
Drive pipes into holes 3 1/4" deep
Construct your shelf with braces to be located at the side of each pipe.
Bore holes in the back of she shelf for pipes to penetrate shelf area.
As there is no way you are going to get those pipes level anyway, use shims to level it all out until it all looks straight. Use metal "U" shaped pipes clips and secure pipe to the braces.
Install the shelf bottom.............and "Bobs ya Uncle"
This will hold 200LBS easily

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