DIY Concrete Countertops Tutorial: Part 1 – Materials & Prep Work Needed

When it comes to home improvement, it is pretty common knowledge that the most valuable investments are in kitchens and bathrooms. However, they have a way of breaking the bank. Other than painting cabinets, there is usually not much room for DIY work in a kitchen. It requires creativity to really save money in a kitchen renovation. One way to do this is by DIY-ing your countertops. At the LaRancharita Flip, we made DIY concrete countertops and we’re excited to share the process.

{Pssst … Are you an avid DIYer? We have more tips and project ideas here}.

Ready to take on a unique and eye-catching kitchen DIY?

Making your own concrete countertops takes a lot of steps, so we are going to break this article into two parts:

• Part 1: Prep Work for DIY Concrete Counters
• Part 2: DIY Concrete Countertops: Pouring and Installation

DIY Concrete Countertops: Prep Work

While I would rate the skill level required for this project as low, the process does require a great deal of time, patience, focus on detail, and a few quality tools. However, this article should give you the information needed to fabricate DIY concrete countertops.

*Full disclosure: This DIY project is a lot of work and probably not the best option for house flippers or home renovators, due to the energy and time involved. But for those daring enough to try, who have access to the appropriate tools, and want to save some money, there’s significant cost-saving potential. 

Tools Needed FOR DIY CONCRETE COUNTERTOPS:

• Table Saw
• Chop Saw
• Drill
• Compressor
• Finish Nail Gun
• Concrete Mixer
• Wheelbarrow or Bucket
• Finish Sander

Materials:

• 4×8 sheets of Melamine
• concrete
• 1 ½” finish nails
• 2” screws
• black silicone caulk
• mineral oil
• rubbing alcohol
• sink
• faucet
• 1 ½” insulating foam (typically pink or blue 4×8’ sheets)
• galvanized perforated angle iron
• all thread couplings ¼ bolts ½” long
• washer to accommodate
• galvanized metal mesh or concrete fibers

Having all the materials in advance saves on project time and slows the inevitable graying of hair from runs back and forth to Home Depot.  

DIY CONCRETE COUNTERTOPS Prep: Measurements & Molds

It is very important to take your time during each step of building molds because mistakes are hard to fix once you pour. Standard countertop depth is 25 1/2 ”. This will give you approximately a 1 ½” overhang. If you have an island or a peninsula, be sure to give yourself enough room for the overhang on all appropriate sides.

Assume Nothing When Measuring

Draw an outline of your cabinets on paper, and measure each dimension, allowing the 1 ½” in appropriate places for overhangs. 

It is very important to make sure you have measurements for the center point on your sink, as this will help you template it later. Then once you have all your measurements laid out, you are going to want to determine how you will divide the countertop. 

Your pieces will be poured into 4’x8’ molds, so allow this to guide your thinking and plan. The purpose of the foam is to prevent the concrete from going where you don’t want it to go. 

Make a Template: the Sink

Once you have your sink, you can begin by making a template out of the foam board. The sink purchased for #larancharita came with a template, so it was easy enough to trace that onto the pink foam and cut it out. Not all sinks will though.

There are two common types of sinks:

• For Drop-in Sinks:
  • You have more wiggle room in templating.
  • Template for the concrete to extend under the outer edge (lip) of the sink.
• For Undermount Sinks:
  • Important to be accurate in measuring.
  • Measure your sink’s interior dimensions around the top edge.
  • You will want your counters to extend slightly over the edge of the sink, but right on will look best.

*Note: It is possible to pour the portion of the counter with the sink in one piece but it has a high risk of breaking. Our design plan included  pouring rails in front of and behind the sink to avoid this, so for the purposes of this article, we will discuss that method.

As you can see in the image above, we had to extend the two sections of the counter that surround the sink 4”, then create separate molds for the sink rails. 

Since you have your sink dimensions, trace them out on your pink foam. Use straight lines and right angles at first. Once you cut it out, sand away the corners to match the contour of your sink.

**With concrete it is helpful to remember you can always sand material away but it’s really hard to add material later.

Next, take the finished piece of pink foam that you have specifically templated for your sink and cut 4” off the right and left side. These 4″ pieces will be mounted within the molds that are connected to the sink. Like this:

Now, grab another piece of foam board and using a table saw, rip down 3-4” pieces of foam the full length of the foam board. Set them aside. These pieces will be installed like this to create the edge of your counter:

At this point you should have your sink measured and foam cut and have your dimensions for your countertop on a piece of paper.

Before moving on, number each section of your counter.

Concrete Countertops Assembly

You got a sneak peek with the images above, but now it is time to assemble your molds. You will begin by cutting rectangles out of the melamine. If you are just doing a straight counter, you can cut them to the exact dimensions. If your counter has a corner, you will have to cut a rectangle large enough and wide enough to accommodate the negative space.

Once you have the face molds cut out, you will need to use the table saw to rip down pieces of melamine to create the concrete depth. We chose to do 1 ½” to cut back on material costs. This is a standard thickness for granite.

*TIP* It is common for people to do 2” concrete counters. Whatever you choose, you will need to cut the strips that will go around the edge of your mold so that they are thick enough to accommodate your full counter thickness, plus the thickness of the melamine and add an 1/8th of an inch to give some margin for error. With our 1 ½” counters, we made 2 3/8” strips of melamine.

Now, cut your strips so they are about 2” longer than your mold. Then you will cut a block that is exactly 1 ½”.

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This will be your guide for nailing in the edges of the molds. Take your block and your first strip. You will hold your block flush to the face of the mold. Then take your strip and set it so it is flush with the end of the mold. Nail it in, checking every few inches to make sure it is exactly 1 ½”.

*TIP* When nailing, be very careful not to nail through the face of the melamine. It has a tendency to soak moisture and can swell up leaving significant blemishes in the counters. If this happens, dig out the hole slightly deeper than the surface. You will be able to fill it with silicone to waterproof it.

When your first piece is nailed, take your second piece and nail it so that it butts up to the side that extends longer than the mold.

Continue this process, nailing every 3” and making sure your edge pieces are 1 ½” exactly. Now, if you are working with a corner section, take the 3-4” strips and cut them so they are the proper length to outline the negative portion of the mold, ensuring they are set at the exact counter depth.

*TIP* Remember, your molds need to mirror the actual shape you need. This is because you are pouring the counters upside down. When you flip them right side up they will be correct.

You are going to secure the foam to the molds with washers and screws long enough to go through a washer, the foam and into the melamine.

Setting the Faucet Hole

When setting the sink, make the front edge 4”. This will push the sink forward allowing for a faucet to be installed in the back. Make sure the 4” pieces you cut line up with the sink mold so that they fit perfectly after pouring. At this point, you will also want to cut a 1 3/4” circle out and screw it in place where the faucet will be mounted.

If you are planning to have in-counter soap dispensers or a spray hose, you will want to determine how big to make those pieces and you will want to install the foam where the negative space should be.

Mounting Brackets

Next, you will take your perforated angle iron and cut it, using an angle grinder with a metal blade, into roughly 4” pieces so that one end at least has a whole circle. (See image above).

You will then take your ¼” bolt and run it through the hole on the metal. You will screw it into the all thread coupling. On the other end, you will run a second ¼” bolt through the washer and into the coupling. The washer and bolt will have concrete poured around them. These will support your sink later on.

Take your bracket and mount it so that when you pour the concrete the washer side of it will be mounted in the concrete. You want it to extend an inch and a half past the foam. You will then take a washer and screw and mount it to the foam. All thread coupling is ¼”.

Final Countertop Prep Work

Now, wipe all the molds clean. Go around with the black silicone and caulk all the edges of the mold to ensure none of the concrete spreads into cracks or under foam. Run your finger along the seams to make a smooth rounded edge.

*TIP* It is a good idea to use a bit of old t-shirt or smooth cloth to help keep silicone off of your hands.  

Finally, let your molds dry completely. This may take several days. 

Next time we will learn how to pour concrete...