Project Guide

DIY Concrete Countertops

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Build the Form

In addition to increasing the height of the counter, a thicker countertop reduces the space between it and the kitchen wall cabinets. Some building codes require an 18-inch clearance from the top of kitchen counters to the bottom of the upper cabinets. Keep this in mind when forming concrete countertops.

  • Place a sheet of 3/4-inch melamine particle board that is larger than your finished dimensions on two sawhorses. The cement you’ll be using is heavy, so use a couple of 2- x 6-inch boards stretched between the sawhorses as additional support for larger countertops.
  • Mark the dimensions of your countertop on the panel.
  • Use a table saw to rip 1-1/2-inch wide strips (or the thickness of your countertop) of the melamine for the sides of the mold.
  • Measure and crosscut the strips to length. The strips used for two sides of the mold will be used as an abutment to the other edges, so they should be cut 1-1/2-inches longer than the countertop dimensions to accommodate for the thickness of the melamine board.
  • Clamp the pieces in place on top of the base panel, drill pilot holes in 12-inch intervals and use course-thread screws to secure the form.
  • Apply a bead of silicone caulk inside the mold at each corner joint and around the perimeter.
  • Run a wet finger along the silicone to smooth it, pressing it into the joint and creating a rounded edge. Use a dark color of caulk to make it easier to see the excess that you’ll remove later.
  • If your countertop requires a cutout for a sink, cut a piece of 1-1/12-inch foam insulation panel to the dimensions of the opening you need. Glue the foam to the base of the countertop form in the proper location. Use painter's tape around the edges of the foam to prevent concrete mix from seeping in.
Prepare the Form and Reinforcement
  • While the caulk cures, cut re-mesh reinforcement to fit inside the mold with a 2-inch gap around the edges. Remove the re-mesh for later use.
  • When forming concrete countertops, the bottom of the mold will be the top of the counter, so any imperfection on the surface of the melamine will show up on your finished countertop.
  • Peel off the excess material that was pushed away from the mold joints when you smoothed the silicone bead.
  • Clean the inside of the form with rubbing alcohol.
Pour the Concrete

Mix the cement to the desired consistency and add any pigment, if using. Consider concrete tool rental for your big project. It will thoroughly blend the mix with much less elbow grease than mixing by hand. Choose a high-strength concrete mix - it doesn't need to be a countertop mix, but that variety is also available. Work quickly when pouring concrete countertops, but don't be sloppy or careless.

  • Scoop, shovel or pour the concrete into the countertop form. Use enough of the mix to fill the mold about halfway up the sides.
  • Wear hand protection and press the concrete mix into corners to ensure proper coverage, eliminate any large air pockets and roughly make level.
  • Place the re-mesh on top of the mixture, keeping it about 2 inches from the sides.
  • Continue adding fresh concrete on top of the wire mesh, being careful to not press it down.
  • When the mold is filled, use a back-and-forth motion with a straight piece of lumber to screed across the form from one end to the other to level off high points and identify low spots. Add more concrete if necessary and screed again.

Tip: Now is a good time to remove any wet cement that has gotten into the screw heads holding the form together. This will make disassembly easier when the time comes.

Remove the Air Bubbles
  • Smooth the surface with a float.
  • Agitate the form with an orbital sander with no sandpaper. Move along the underside of the form and the sides. Alternatively, use a rubber mallet to tap underneath the form and along the sides to help the bubbles rise. 
  • Use the float again to smooth the surface where air bubbles have risen.
  • Make another pass around the form with the sander and once again, use the float to eliminate any bubbles.
  • When the concrete has started to stiffen, use a trowel to achieve a smooth surface. Even though this will be the bottom of the countertop, it should be smooth to rest evenly on the base cabinets.
  • Loosely cover with plastic sheeting to help prevent it from drying out while your project cures.
Remove the Form

After four days (or a week, if your DIY time is limited to weekends), remove the concrete countertop from the form.

  • Remove the screws that were holding the form together.
  • Insert a putty knife into the side joints with gentle taps of a hammer.
  • Carefully pry the form sides from the concrete.
  • Use the putty knife and shims along the perimeter of the countertop to loosen it from the particle board base.
  • With a helper (or helpers), lift the slab and remove the base melamine panel.
  • Turn your new countertop over and rest it face up on the sawhorses.
Slurry, Sand and Seal
  • Sand the countertop surface and sides to expose any air bubbles near the surface using an orbital sander and 80-grit sandpaper.
  • Mix a slurry and include the same pigment ratio if your concrete is tinted. 
  • Put on some rubber gloves and spread it over the entire surface to fill and smooth over any voids.
  • Allow to dry.
  • Sand the entire slab again using the orbital sander and 80-grit abrasive. Wipe clean and switch to 120-grit. A final sanding using 220-grit abrasive will leave a smooth polished surface.
  • Vacuum the countertop and then wipe with wet cloths to remove all dust. Allow to dry.
  • Concrete is porous and can easily stain, so it’s very important to use a concrete sealer to help prevent permanent blemishes.
  • Choose a food-safe variety if your countertop will be used in the kitchen.
  • Apply the sealer according to package instructions. In general, this will require multiple coats and is a required step to protect your new DIY concrete countertop.

While learning how to make concrete countertops is not a complex task – build a mold, fill with concrete mix, wait for it to cure and then polish it – it’s still a good idea to practice on a smaller scale and hone the techniques you’ll use for the full-size DIY concrete countertops. Make several small forms and adjust the consistency of the cement mix, experiment with pigments to achieve the color you desire and get a feel for using the sander. 

Shop online and gather all the materials you need for your project. The Home Depot delivers online orders when and where you need them.