In this project, I'm going to show you how I built my custom DIY concrete sink for my master bathroom, which saved me hundreds of dollars as opposed to having one made for me.
Step 1: Materials and Tools
Depending on the size of the sink you are creating, you'll likely need some of or all of the following materials. The sink I created is 21" x 48". I purchased many of the products I used in this build from Expressions LTD, and while some of the components were quite expensive, it is still a much cheaper alternative to ordering a custom sink.
- Rough rock edge liner (optional)
- Sink mold
- Mold release wax
- Rubber sink knockouts (You could save yourself some money by using foam instead)
- Denatured alcohol
- 2 pieces of 48" rebar or wire mesh
- Crete-Lease release agent spray
- Quikrete 5000 or a similar concrete mixture
- Melamine sheets for form
- Concrete vibrator, sander, or sawzall (without blade) to vibrate form
- Fine-grit sandpaper (120/220 grit)
- Turbo cup wheel
- Angle Grinder
Step 2: Building the Lower Form
The sink form I built is 50" x 21 1/2" x 2" deep because I want a half inch overhang around the vanity top sides and front. (the rough rock liner adds an additional 1/2" on each side) The form is screwed together with drywall screws and then use silicone to seal all the edges and hold the liner in place if you're using it.
You can use any color silicone you like, I used black because it is easier to see against the white melamine.
In the center, attach the sink mold. Measure and trace the area where you want to attach your sink mold. Then, attach the mold to the melamine with a small bead of silicone sealer at each corner. This will help level the mold initially, then run a bead of silicone along the outside edge.
I've coated the mold with 3 coats of mold release wax to prevent the concrete from sticking. I also have 3 rubber sink knockouts that are siliconed in place where the fixture will go. Make sure you know what sink fixture you are going to use first so you will know where to place your knockouts and how many you will need.
Step 3: Building the Upper Form
Next, build the second part of the form on top of this base. I'm building this second part of the form separate from the base to prevent excess debris falling into the pour area. Once the second form is built, it sits on top of the first form. The box is 2" wider than the sink mold on all sides and sloped in the front to follow the slope of the sink mold.
Clean the entire form with denatured alcohol to get rid of any excess silicone and debris. Then add a thorough coat of a release agent spray to help prevent the concrete from sticking to the edge liner and sink knockouts.
I also have 2 - 48" pieces of 3/8" rebar to help reinforce the vanity top. I'm placing one in front and another in back to help support any additional weight. You can also use wire mesh throughout if you choose.
Step 4: Pouring the Concrete
Start by filling in the lower form with concrete. This part may seem simple, but it will be pretty labor intensive. Once you've filled in the lower form, vibrate it to remove any bubbles. Now, add the upper form on top of the mold and fill this area as well. Make sure that there are no small gaps or holes where the concrete might fill in, or it might cause you some headaches. (Happened to me because I had a small gap)
Once you've poured in all the concrete (mine took almost 3 bags of Quikrete 5000) cover the wet concrete in plastic and let it sit for 4 days before removing the forms.
Step 5: Refining the Sink
After the concrete has cured for about 4 days, you can now begin removing the liners and the mold. Once they are removed, go over it with some fine grit sand paper, which should help expose any remaining bug holes that will need to be filled.
Then hit it with a slurry coat, a very fine cement that helps fill the small holes and gaps created during the drying process. You can use pure portland cement for this or buy a slurry mix. Go over the surface of the sink and ensure that these holes are filled and the surface is smooth.
Use a turbo cup wheel on an angle grinder to grind down and clean up the dried concrete if you need to. Mine was a little uneven on the bottom of the sink itself so I decided to clean it up a little bit. This is a good time to deal with any balance issues or imperfections you might come across on the underside.
Lastly, add several coats of concrete sealer if you choose to. You can also add an acid stain to give your sink a different colored look if you choose to, but if you're like me, you may choose to keep the raw concrete look.
Step 6: Finished!
And that just about does it! Check out the video to see the whole build in process and I also talk about a couple mistakes I made as well, so that you can avoid encountering the same hurdles in your project.
If you liked this project, check out some of these other DIY projects:
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Thanks for checking out this project!