How to Make Concrete Countertops

Mix your concrete. Use a mix for the color and additives that is especially designed for countertops or floors. This is important, as you'll want strengtheners and other filler materials to make your concrete function better for this purpose. You will also want to use a pre-mixed, high strength concrete. Your local home improvement store should be able to help you locate both of these products.

• Mix the concrete in a moving mixer, in order to get the right volume and consistency. These can be rented from your local hardware store. You want a roughly peanut butter-like consistency.^[4]
• Follow the manufacturer's instructions for mixing the concrete and additives. Generally, less water is used for high strength concrete than normal concrete.

Scoop about half your concrete into the mold. Using a shovel or scoop, pour your concrete into the form until it reaches the top edge of the form all the way around.^[5] Use a trowel or paving tool to even out the top and push all of the concrete out to the sides as you work

Add your steel re-enforcement over the first half of concrete. You can also add extra strength by cutting and placing a steel mesh in the wet concrete halfway through the pouring process, so that it is completely entombed in the material. This isn't completely necessary, but is important for preventing cracks and creating a countertop that will last a lifetime.^[6]

Continue adding the last half of concrete over the re-enforcement. Err on the side of having too much concrete in the form. You can always skim some off, but it is much harder to add in later.

Screen the top of the form. Using the edge of a flat board, lay it across the top of the form on one end and then slide it back and forth as you move down the frame to the opposite end. This will take off any extra concrete and make sure the top is level. You can use the edge of 2x4, or speciality concrete working tools. Work the edge back and forth along the top, like you are leveling floor in a measuring cup, to distribute the concrete evenly.

• Take any excess concrete and use it to fill in any low spots.
• Extra concrete should be held onto for later, as it may help fill in spots.

Vibrate the edges of the mold to release air bubbles. Vibrate the whole table your form is resting on if you can, but at a minimum gently vibrate the sides of the form to get rid of any bubbles. You can use a sander on a low setting, without any attachment, and run it along the entire edge of the form, for the easiest solution.

• Your goal is to get an nice, even top. Even just lifting and dropping the whole table 2-3" inches, bouncing it rapidly, is perfect.
• You can also use a rubber mallet, striking the sides of the mold and bottom of the table.

Use a float or trowel to smooth out the entire top of the concrete, and use and edging tool to bevel the entire edge. Smooth everything out, then create a nice, rounded edge around the entire mold. Then trowel out any imperfections created by the edging tool, and let it sit.

• Repeat this process again, especially the troweling, after 2-3 hours.

Allow the concrete to cure. Cover the concrete with plastic and then allow it to cure as long as instructed by the manufacturer. This could be anywhere from 1-2 days to a week. However, you don't want the concrete to completely dry. When you can press into it and only create a small dimple, you're ready to move forward.

Release the forms when the top is firm, but still slightly pliable. Unscrew the sides of the form and gently pry the melamine off of the concrete. If the concrete starts to slump, put it back on. If not, use your trowel to smooth out the outside edge of the counter into a clean, even surface.

• If you need, a small spray of water makes the concrete a bit easier to work with. You won't need much.
• If a little concrete pulls off with the wall, you can trowel some of the excess concrete back on with a spritz of water.

Trowel over the top of the concrete as well, waiting until it is almost completely dry. This final troweling provides some smoothness and character to your countertop. It is not entirely necessary, but will lead to a prettier countertop.

With a friend, lift the countertop and remove the mold and bottom. You need the bottom of the countertop to dry, too. Once you're sure it is dried enough that it doesn't slump (in which case you would still have the side walls on, get a friend to help you raise the top of the countertop. Rip out the foam and pull off the molding, exposing the bottom of the counter top.

• Don't rush this. Remember, the concrete should just barely indent under your finger.
• Let the countertop hang over the edge, at least slightly, to allow air underneath to dry.

Clean the countertop once it has completely dried. Put on some rubber gloves and then wipe down the countertop with a mixture of 10 parts water to 1 part muriatic acid to remove any remaining residue and prepare the material for sealing. Remove the excess acid with a squeegee.

Sand your countertops. Using a sander and increasingly high grit sandpaper (120, 180, 220), sand your countertop and the sides until it is completely smooth.^[7] Remove the dust with a cloth and some water.

Paint or acid wash your concrete, if desired. If you want to color the concrete, add it after everything has dried. You can use any sort of coloring you want, as long as it is made for concrete.

Seal the countertop. Using a penetrative sealer, fold a rag as flat as possible and then saturate it in the sealer.^[8] Wipe this in long strokes, overlapping each stroke with the next, until the entire counter is covered. Allow to dry. This usually takes around 2 hours.

Wax and buff the countertop. Use a food safe wax and a buffer to finish the countertops. When they're shiny and the wax is absorbed, you're good to go!