Wood and concrete coffee table
I have just built this wood and concrete coffee table.
I started to like the idea of combining materials that are not usually used together. I saw a few pieces of furniture in combinations of concrete and wood that I liked a lot. I have decided to make this wood and concrete coffee table.
I then sketched a coffee table to build it out of these two materials. The mix between the warmth of the wood and the harsh concrete would give it a very special look. Besides the look, the large weight (over 50 kg) of the legs would make this coffee table ideal for people with small children or pets, since it would be very difficult to topple.
First of all, I built an ash wood panel for the tabletop. I won’t insist with the process of gluing up the panel. An easier way of building a panel as flat as possible is using a 4-way clamping system. We designed and built such clamps. You can download the free plans to build your own 4-way clamps to glue large panels with easy. There is also a video where you will see how this clamping system works.
We decided to secure the wooden top to the concrete legs with metal brackets. In the same time, we didn’t want them to be visible. So, I found a simple solution: I glued up a border on all the edges of the panel. This way I made the brackets less visible.
We built the panel a little bit longer then the final size. We wanted to build the end grain borders by cutting the ends of the panel and gluing it up after turning them on the other side.
So, I cut one end of the panel at 90 degrees angle. I had a 3 cm wide strip. I made the same cut at the other end of the panel. I used each wooden strip at the panel end where it has been cut from.
They had to be glued under the end, upside down, to match the end grain of of the panel. This way the and grain of the coffee table top should be continuous, creating a very nice mirror effect.
After the glue has dried, I glued two ash wood planks on the long edges of the panel.
When the whole panel was bordered, I cut the slots for the concrete legs.
First I made the long cuts with the circular saw using a straight plank clamped on to the panel as a guide.
I finished the cuts using the jig saw.
I also cut the shorter sides of the slots using the jig saw.
For the molds (needed to build the concrete legs), I purchased from a local diy store some 4 cm thick kitchen countertops scraps and some white laminated panels. Before using the counter top pieces as molds for pouring the concrete I sealed them. I first filled the holes with wood putty.
I sanded the excess and then I painted everything with black flexible paint.
In order to secure the metal brackets, I milled slots in the molds. I placed them so that the table top would sit flush to the ends of the concrete legs.
I used some scrap metal pieces to reinforce the concrete. Even though I was sure that the concrete block would be hard enough, I preferred to reinforce it.
So that, the metal brackets would be better secured to the concrete legs of the coffee table.
I mixed the concrete using the mixer that I have in my yard. It helped me to be sure that the concrete is thoroughly mixed.
I then poured the concrete into the molds, making sure the reinforcements wouldn’t not move from their places. I compacted the concrete using a hammer. I hit the mold walls with the hummer trying to compact the concrete as well as possible.
I removed the mold of the first leg three days after the pour, so I chipped it a little because I had to force it to remove the panel with the metal brackets going through it. For the second leg I waited 28 days until I removed the mold. The second one turned out great.
Once both molds were removed, I could finally check if all my calculations were good and if the ash wood top of the coffee table fits to the legs. I had to make minor adjustments. I did them using the jigsaw (to enlarge the cutouts of the table top) and the angle grinder (to sand the concrete legs) so that everything to fit perfectly.
The top ends of the concrete legs were too rough. I couldn’t let them that way. I wanted to sand the concrete. I also didn’t want to invest almost 100 USD to buy a special diamond grinding concrete disc. So I bought a tool for the angle grinder, designed to sand stone, that was a lot cheaper. Since it was designed to polish stones and the concrete is made out of stones, sand and cement, it worked.
I’m sure it took me a lot longer than with a diamond grinding concrete disc, but I did my job.
While grinding, I noticed that applying water makes the concrete much easier to flatten. So I kept on applying water from time to time, using a paintbrush.
Because I was almost sure that the angle grinder might slip on the wooden table top, I put adhesive tape on the wooden panel, right next to the concrete legs. The tape did it’s job by protecting the wood 3 – 4 times when the angle grinder slipped towards the wood.
When I was satisfied with the look of the coffee table, I started to finish all the pieces of the wood and concrete coffee table.
Using a paintbrush, I applied a special resin to the concrete legs.
After the first coat was dry, I applied the second one, to make sure that all the concrete pores are sealed.
I followed the usual steps to finish the wooden table top: I stained it using a sponge. After the stain has dried, I noticed that the ash wood table top looks very similar to a wood that is very expensive around here: the zebrano.
I then applied the water based primer and two coats of matte water based varnish. The matte varnish protects the wood but also keeps the look much closer to the natural wood.
When I assembled the parts, I noticed that the resin gave the concrete a beautiful shine, which didn’t match at all with the matte varnish applied to the table top. So I sanded lightly the top ends of the legs and I applied a coat of matte varnish to them, too. The difference was huge and I am very glad I did that.
Since I had to move the concrete legs around a lot ( I polished them outside, for obvious reasons). I was curious to weight them: around 25 kg each. So, the whole table have around 55 kg. There was absolutely no chance that the coffee table might be moved by a child or a dog.
When I placed the coffee table in front of the couch, I realized that this small coffee table changed the look of the entire room.