How to Make Concrete Countertops: A 16-Step DIY Guide

If you haven’t already measured your countertops when purchasing concrete, you’ll need to get exact measurements to make a mold. Measure your base cabinets, and add 3/4 inch to the length and width to account for overhang.

To create your mold, use a melamine-coated particleboard. This type of particleboard has a sleek white surface that gives your countertop a smooth finish. Place the board on a couple of sawhorses to create an accessible workspace.

Next, use your measurements to draw an outline of your exact countertops on the melamine. This pattern will turn into the base of your mold. Cut out the outline with a circular saw.

Then, you’ll need to build the sides of the mold. Cut strips of particleboard that are 2 3/4 inches wide (or your preferred thickness). When sizing, remember that most concrete countertops are 1 1/2 to 2 inches thick. Once cut, screw the strips into place on the sides of the base; make sure to insert your screws from the outside of your mold so you can remove them when the concrete cures.

Instead of cutting your countertop after the fact, you’ll create the cutouts for a sink, cooktop, or other accessories before pouring your concrete. Make sure you take exact measurements of these accessories and their location on the countertop. If there’s an error, the accessories may not fit when you try to install them. 

Use your measurements to trace an outline of the accessories in their exact location on the base of your mold. Drill pilot holes on the inside corners of each section you plan to cut away, then use a jigsaw to cut out the outline.  

Measure and cut strips of particleboard to use as the sides of the cutouts. Attach them the same way you attached the outer sides of the mold. Clean your mold so it’s free of sawdust and other debris. Debris could blemish the top of your counter once the concrete cures.

To prevent concrete from slipping through the cracks of your mold, you’ll need to caulk around the seams—the areas where the sides of the mold meet the base. If you’re inexperienced with a caulk gun, it’s a good idea to line these areas with painter’s tape and then caulk over the tape. This way, if you make a mistake, you can pull the tape up and try again. 

If your silicone caulk is a little messy, run a wet finger along the caulk before it dries to create a smooth line. Wait 24 hours for the caulk to completely dry, then spray the entire mold with silicone spray or olive oil. This will prevent the concrete from sticking and make removing the mold easier.

It’s worth repeating that concrete countertops are heavy, so creating a support frame for your mold is a good idea. You don’t want the particleboard to bend and warp the shape of your countertop. You can do this by screwing together a few two-by-four boards, cut to size.

Cut at least three two-by-four boards so they’re 3 1/2 inches longer than the base of your mold. Place them on the sawhorses beneath your mold to create the base of your support frame. Center the mold on top. 

Next, measure and cut two-by-four boards for the sides of your support frame. The sides of the support frame should fit snugly against the sides of the mold. Screw the sides to the base of the frame from underneath. Do not screw the two-by-four to the mold itself—only the support frame.

You need to reinforce concrete countertops with galvanized steel mesh, which helps prevent cracking. You’ll add this mesh halfway through the pouring process, but you should prep it beforehand. 

Measure the mesh to create a shape that’s 1 inch smaller than the shape of your countertops. Snip the mesh to size using a metal cutter.

Follow the manufacturer’s instructions to mix the concrete, taking care to add the correct amount of water. There are different methods to mixing, including using a motorized concrete mixer, but a wheelbarrow and shovel (which you probably already have in your shed) will work just fine.

Depending on your kitchen countertop idea, you may want to add a concrete pigment—whether it’s a powder or liquid. Mix it into the concrete following the manufacturer’s instructions. If you use a liquid pigment, you’ll need to adjust the amount of water in your concrete mix so it isn’t too runny. The ideal texture is similar to peanut butter.

Begin pouring the concrete into the mold. Use a hand trowel to help spread the concrete and tamp it down. Fill your mold halfway.

Once the mold is halfway full, add your mesh reinforcement. Place it in the center of the mold, but do not allow it to touch the edges. You don’t want wire showing through the edge of your countertop. 

Continue to fill your mold with concrete over the wire. Tamp it down with a trowel as you go. Make sure to slightly overfill the mold since the level will drop once you settle the concrete. Once it’s filled, smooth the surface with your trowel.

You’ll need to settle the concrete to bring any air bubbles to the surface. Air bubbles ruin the smooth, professional texture of a concrete countertop. They can also cause cracking. To do this, lightly tap a rubber mallet along the sides of the mold. You’ll notice the concrete start to level out—but don’t tap it hard enough that it starts spilling over itself.

Alternatively, you can use an orbital sander without any sandpaper. Run it along the sides of the mold. This should vibrate the concrete enough to bring the bubbles to the surface.

Let the concrete set so that it’s slightly hard but still malleable, then use a hand trowel to smooth the surface. The top of your mold will become the underside of your countertop, so make sure the concrete is level.

Once it’s level, lay a plastic sheet over the top of your mold. This protects the surface from dust and debris while locking in moisture so the concrete can cure slowly. A slow cure will help strengthen your countertops.

Allow your countertops to cure fully. You should wait at least a week before you attempt to remove the concrete from the mold. For the strongest countertops, wait two weeks.

Once your concrete has cured, you can remove the mold. Start by removing the screws with a drill and pulling the sides away. The melamine particleboard should smoothly release if you used silicone spray or olive oil. 

Once the countertop is out of the mold, turn it over. The top of the mold is actually the bottom of your countertop. This way, your countertop is less likely to have visible air bubbles. Be extremely careful during this process as the countertop can be quite heavy.

If you notice any cracks or bubbles, you can repair them using a concrete patching compound. Apply the compound per the manufacturer’s instructions. Allow it to cure fully, then use an orbital sander to smooth the surface. 

You can also use your sander to smooth rough corners. Start with 100-grit and move to 220-grit. Since this kicks up a lot of dust, you should wear a respirator. 

Afterward, thoroughly clean the surface of your countertop (avoid acid-based cleaners, which can damage concrete) and allow it to dry.

Since concrete is porous, you’ll need to seal your countertop to prevent staining. Per the manufacturer's instructions, apply a concrete sealer using a sponge or brush. Typically, the sealant only takes about 30 minutes to dry. Once your countertop is sealed, it’s ready for installation.