How do I attach legs to a concrete table top?
October 10, 2015 2:15 PM   Subscribe

I plan on making a dining table top similar to this I am considering a few ways to make the table. One is to use a slab or two of some kind of inexpensive wood or melamine and then spreading a thin layer of the concrete mix on top. My reasoning is that it will reduce the weight of the table.

The other option is to create the frame the way it’s done in the tutorial and make it entirely from concrete. Maybe using a light weight or featherlight concrete.

For the table legs I would like to use metal hairpin legs or something similar. How would I attach them to the concrete table? And would the legs be able to support the weight of the table? I really really want this to be stable.

Another issue is that our car doesn’t allow the back seats to fold down. Can we create a stable base or frame for the table made from pieces of wood/melamine that have been cut and glued together?

Obviously I’ve never done this before. If any of the above is absolutely the wrong way please let me know. I don’t want a table that cracks/slides/collapses onto a knee, foot, kitty, or worse.

Bonus for suggestions on what style chair would go best with this kind of table.
posted by mokeydraws to Home & Garden (12 answers total) 4 users marked this as a favorite
we have some concrete tables (not made by me). the concrete was clearly cast in a mould lined with plastic (you can see the folds of plastic at the edge of the table). the legs are free-standing, welded, with legs that are just "outside" the table and rising to the level of the table top. so the top then sits on the free standing frame, held from sliding by the legs.

since it requires welding this may not be how you want to go, but i thought i'd throw it out there. also, the table tops are in two colours (i guess a second colour was poured into the centre of the mould soon after the first), which might be interesting to experiment with.
posted by andrewcooke at 2:30 PM on October 10, 2015

If you do the lightweight option you might want to search Hafele for appropriate table legs/table leg attachment hardware.
If you go the solid, heavier route you should consider casting some kind of wood block (or attachment hardware) INTO the concrete at the corners (or center?). Just make sure it's of the proper dimensions so that your pre-fabricated legs will align properly and deep (thick)enough that the fasteners (screws) will embed fully.
Would love to see the results!
posted by bird internet at 2:46 PM on October 10, 2015

I would be very worried about putting hairpin legs under a large and heavy concrete table top if I were building a dining table. The legs may be fine to support the weight of the table top as long as they are perfectly perpendicular to it, but if you add any kind of shear force (a push from the side when moving it or if someone bumps into it) you risk collapsing the whole thing. Once there is a bit of sideways loading on the legs, they are likely to fail at the point of attachment to the table.

That's why the table in the link you provided has all the bracing and support. You need serious support for such a heavy table top, even more so with a dining table sized slab. You definitely need a frame that stands on its own that you place the concrete on. If you want a the steel look, perhaps you could look into getting something welded for you.
posted by ssg at 2:48 PM on October 10, 2015 [2 favorites]

You can embed steel rods (minimum #4 rebar) into the casting if you don't want unsightly bracing holding back your design.. Of course that's a lot of extra weight, but a monolithic table could be cool..
posted by bird internet at 2:53 PM on October 10, 2015

And the material you use to strengthen the concrete is steel (which is embedded in the concrete). Any kind of plywood, wood, or MDF underneath the concrete will easily flex enough to crack your concrete, so will effectively provide no support at all.
posted by ssg at 2:54 PM on October 10, 2015 [1 favorite]

A thin layer over wood will not work for any length of time. The concrete would quickly fracture and fall apart.

For mounting the legs, you need to embed anchors into the concrete during casting. I would use large lead anchors rather than wood. I've done something similar with a feature of a concrete countertop I cast several years ago, and did it by suspending the anchors in the correct locations, hanging them under wood strips spanning the mold. If you use anchors that are open on the far end, remember to plug them with clay or something so they don't fill with cement.
posted by jon1270 at 2:58 PM on October 10, 2015 [2 favorites]

One is to use a slab or two of some kind of inexpensive wood or melamine and then spreading a thin layer of the concrete mix on top

I only have a few minutes but will respond with more info later if needed. If you decide to go the thin-coat route, here's some info.

I did my kitchen countertops using thinset concrete over plywood and Hardie Backer. Here's a link to an album of photos of the whole project, but the countertop part starts about 15 photos in. I don't see why the same method wouldn't work for a table top.

The basic method uses a product called Ardex Feather Finish or Henrys Feather Finish. It's very easy to work with but has a short workable window of 15 minutes or so. It's meant to patch concrete floors and similar uses, but people have been using it for countertops with mixed results, depending on method and expectations.

If you search for "Ardex Feather Finish countertops" or similar, will find tons of info, but I ended doing mine slightly different than any of the online resources showed. Here's a link to one blog that shows the process.

The main difference in my method is that I did NOT sand it smooth. I wanted a more organic look, and, frankly, didn't want to deal with concrete dust! So, I put down the feather finish as smoothly as I could with a large drywall taping knife, and used a smaller putty knife for the edges. I did 3 layers altogether, then when the the last layer was cured, I used a putty knife to just knock down any edges or high spots.

I then sealed it with 511 Impregnator Sealer, followed by several coats of Acrylacq Sealant.

It's been almost a year, and I love the results.

Caveat: If you want a perfect and impervious surface that will never need maintenance and never get blemished, then this is not for you. It will change over time, and will need additional applications of the finishing sealant every 6 months to a year. It may get spots from use, and some things can stain it, even through the sealant. (You could seal it with floor-grade polyurethane for more durable surface, but I used what I did because it is food-safe.) The area around my stovetop actually got some quite dark patches from splattering oil. The good news is, it's pretty easy to repair any damage or stains. Just sand off the sealant and apply another thin coat of Feather Finish to that area. After I repaired the area around the stovetop, I now keep a glass cutting board there to use as a trivet and protect the countertop from oil.

As I said, I love the results and my wife does as well. I get tons of compliments on it.
posted by The Deej at 3:01 PM on October 10, 2015 [5 favorites]

The top in the tutorial is so thin that just anchoring the legs into it wouldn't make any sense unless the legs are welded to a rigid internal frame, not just held by the concrete. A couple of sturdy trestle legs might work but the one I see at Ikea all look pretty flimsy.

I know this isn't the answer you want to hear but I wouldn't consider this a beginner's project. I'd suggest building a wood table and painting it for the effect you want. Less inherent danger. Danger is not a thing you want to be dealing with on your first project. If you want a good book on building a table with hand tools, memail me.
posted by bonobothegreat at 10:09 PM on October 10, 2015

Response by poster: Thank you all for the very helpful responses! If I'm understanding the tutorial that The Deej linked to I can use plywood and cover it with the featherwight finish? I would be able to attach legs to the plywood underneath and this would be considerably lighter? Can the featherweight finish be stained or dyed? Ultimately what appealed to me is that concrete can be dyed and or stained and I really loved the variegated look that you can get.

bonobothegreat I didn't want to hear that but I suspected as much. I will probably try it with a smaller table once I have a better plan for a base.
posted by mokeydraws at 3:16 PM on October 11, 2015

The thing with those hairpin legs is that they're used on tables with plywood that is veneered, or I've seen mosaics, but basically something that can flex a little without being destroyed, which is what you're fighting against with the concrete. It don't know how brittle the lightweight stuff is,, so maybe it's worth a try. But be aware that even thick plywood can sag over time. Where I see hairpin legs the most is on those honking big "live edge" slab tables, which is perfect because the slab is thick enough to support itself and even if it starts to crack, it generally just adds character.

Most table tops need some kind of apron for support. I really like a book called The Essential Woodworker, available here as a $12.00 download. It's a hand tool book but it covers all the basic construction methods.
posted by bonobothegreat at 4:16 PM on October 11, 2015

If I'm understanding the tutorial that The Deej linked to I can use plywood and cover it with the featherwight finish? I would be able to attach legs to the plywood underneath and this would be considerably lighter?

Yes, exactly. I would recommend building the table, then do the Feather Finish as the last step so you don't have to manhandle the tabletop once the concrete is applied.

Can the featherweight finish be stained or dyed? Ultimately what appealed to me is that concrete can be dyed and or stained and I really loved the variegated look that you can get.

Yes, it can be dyed, although I didn't use any. I have seen other blogs that describe the process. There is a special (powder?) dye that can be added.

Also keep in mind that the method I used resulted in a variegated look due to the varying of the thickness of concrete during the application. The photos I link don't really show this very well, but it's very evident in person.

As far as the the danger of flexing, as mentioned by bobobothegreat, that is a concern, but I think you will be ok if you use 3/4 inch plywood and include an apron in the design as bonobothe great says. Maybe a cross-brace beneath would also be helpful, depending on how big the table is.
posted by The Deej at 8:30 PM on October 11, 2015

Wanted to add... I did Henry Feather finish for my kitchen counters (over solid wood - I want to say birch, but don't remember exactly - my cabinet maker did the wood part).

Two things:
1) To get a variegated look, I alternated the direction I applied the concrete between layers. The tutorials on Kara Paslay Designs helped me decide to do this.
2) I sealed with tung oil, and once that was cured, polished with a beeswax/mineral oil mix. The tung oil darkened the concrete to more of a charcoal finish, which was perfect for me. It looks like the whole countertop is a carved piece of stone. Between the tung oil and beeswax, water just beads right up on the surface. It's been over a year, and we don't have any stains, or any other noticeable wear. They look as good as they did at the beginning.

Feel free to memail me if you would like more details.
posted by slipthought at 5:57 AM on October 15, 2015 [1 favorite]

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