Floating Concrete Table With Planter

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About: I'm a 16 year old Maker with a youtube channel and a workshop which never gets cleaned! I hope you'll enjoy my tutorials!

Hi Makers!

In this instructable we’ll be making this seemingly floating concrete table, which can be made in a weekend! The only two things really required is steel square tubing and some concrete. It features a planter and a light bar which lights up the ground. It is also easy to scale this project up, with some minor modifications in the construction. Let’s get making!

Supplies:

Step 1: The Design

The design idea for this project came out of mere curiosity. I was thinking about this idea to make something we all know is heavy, seem to float. And so this design was born. I considered glass as an early option for the top, but leaned towards concrete as I wanted a planter in the center. I really had a concrete plan! (Did you see what I did there? ;) )

I opened my CAD of choice, Fusion 360 and made this simple model!

Step 2: Choosing the Materials

To make this table you will need a welder. Now, this project is actually the reason I bought one, and this is also my first project using it, so I’m still learning. Alternatively, if one isn’t available near you, you could try using screws, but it would be difficult. So as mentioned, you will need a concrete mix and square steel tubing, I used tubing with the dimensions of 20 by 20 millimeters, which translates to around 4/5 of an inch. If I were to do it again, I would probably choose something beefier, maybe 30 millimeters since my table has just a slight rocking to it when heavy objects are placed on top.

The dimensions for the steel frame can be found above!

Materials used:

  • 4x 1-meter lengths of 20x20mm

    square steel tubing (though I highly recommend thicker tubing than that)

  • Concrete mix (I used a stronger kind)

Step 3: Cutting & Welding the Steel

Anyway, I started by marking and cutting the tubing. This would be much simpler and more precise with a band- or miter saw, but since I only have a small metal saw and a miter box, I used what I had.

After that was done, I started up the welder, and started welding. Well, not exactly. See, I thought welding would be a piece of cake, but it actually turned out to be quite challenging. I had quite a lot of fails, one even blew the fuse! Somehow though, I succeeded in welding all 8 joints in a way that this table hasn’t collapsed to this day. Now I call that a success!

When welding, be sure to use all types of protection, as it is extremely dangerous to look directly into the welding arc. High current and hot metal are also dangers that come with welding. Welding helmet/goggles, gloves and appropriate clothing is all necessary!

Step 4: The Welding Result and Wiring

Well, the welds weren’t exactly of astonishing quality, but I proceeded without redoing it, since I was short of welding rods. Some joints looked nicer than others, but you get what I mean.

As I wanted to have a light which would shine down onto, well, not the legs, I wrapped a piece of wire around the top part of the steel and drilled a pair of holes through one leg, and pushed the wire through the tube.

Step 5: Building the Concrete Mold

I built a mold for the concrete which had the inside dimensions of 60 x 50 x 10 centimeters. The reason I chose polystyrene over melamine for example, is that the foam has an interesting texture which I think will be a good match for my industrial-look which I envisioned. Also, it is cheap, which i like. If you are looking for a marble-design, then I recommend a mold material which is smooth. Nevertheless, I cut and glued the walls to the base using hot glue, nothing fancy here.

I marked where the steel structure would sit, and precisely measured and cut (in my case 8 centimeter long) skewers, which I later pushed down into the foam within the marked areas to act as standoffs. If you are using melamine, then pre-drilling the holes will be necessary. I also secured a piece of foam to the center, which is where our plants will later go. So even though I mentioned that you’ll only need steel tubing and concrete, I just wanted to make sure that the table wouldn’t collapse. As reinforcement, I used what I had laying around, in my case chicken wire, but fiberglass mixed into the concrete will provide even better results.

Step 6: Pouring the Concrete

Next, I mixed a batch which was somewhat dry, but it ended up working fine. I placed, more than poured the concrete into the mold and positioned the steel frame on top of the skewers. I continued pouring several more rounds of concrete, with more water added, while making sure the wire that I added before, was above the layers. I used a stick to force the concrete down into the crevices, and poured a few more batches, until it reached the 8 centimeter mark on the sides (thus a 2 cm margin on the top).

After the last layer was poured, I flattened out the top (which is also the bottom).

Step 7: The Moment of Truth & Sealing the Concrete

After the last layer was poured, I flattened out the top, which is also the bottom. Anyway, after twenty four hours, I removed the styrene which revealed a not completely dry table. So I waited another day. Then, I flipped it upside up, and removed the foam from the top as well. I then pulled out the skewers, revealing a few nasty holes, but don’t worry. Next, I sifted some concrete through a strainer, and applied the fine mixture as a top layer. When that had dried, I applied a concrete sealer which will make the surface dustless.

Step 8: Choosing My Plants and Certain Problems...

Ideally, you would plant something useful in this, like herbs. But since this will be right next to my bed, I wouldn’t like the constant smell of rosemary or such, so I'll be planting cacti, since they require little maintenance. But here is another problem; when reaching for the phone in the middle of the night, I could get splinters all over my hands. So I wanted to have a sheet of glass on one side of the cacti, to protect my hand.

First, I needed to cut the glass though. I was thinking of scoring it and heating it u.... I was thinking of using a diamond bla.... You now, let’s just ditch the glass. So I cut a sheet of aluminum to size, and roughed up the surface. I applied silicone and secured it in place. While I was at it, I also used the silicone to fix the LED strip to the underside. To protect the plants from the concrete, and vice versa, I covered the entire pot section with a food-safe, aquarium silicone.

Step 9: Adding the Cacti

After drying, I placed some clay balls in the bottom to act as a water reservoir and added the three cacti of my choice. I also placed my D-day diorama on side of the plants. After hooking up the light strips to a power source, it was finally done!

And I must say it looks absolutely amazing! I am so happy with my design choice, with the combination of industrial design and nature, along with history.

Step 10: The Result

I hope you enjoyed this instructable! If you did, maybe there's something on my Youtube-channel that might also interest you! If you're making this project, then I would love to see your results, DM me the pictures on Instagram (@pew.tech)

I will see you another weekend!

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    4 Discussions

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    OliverM18jessyratfink

    Reply 26 days ago

    Thanks :) Yep, acanthocereus tetragonus are among the most pleasant cacti. Comparably no spines, just the "classic", beautiful shape.

    0
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    OliverM18seamster

    Reply 4 weeks ago

    Haha yeah, around 50 kg! Thanks for the comment!