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How To Make Concrete Countertops

Concrete Countertops

Disclosure: This article is sponsored by QUIKRETE. The product links below may contain affiliate links. I receive a small percentage if you purchase via those links. However, this in no way changes the price for you. Also, as an Amazon Associate, I earn from qualifying purchases.


Table Of Contents


Concrete countertops are very attractive and look great in contemporary kitchens and bathrooms. They are heat-resistant, durable, and relatively inexpensive to make yourself (When purchasing them, prices are comparable to granite or quartz, though).

Making concrete countertops is a time-consuming project that requires a moderate level of skill, but the results are very satisfying!


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Tools, Supplies, PPE, and Steps

I’ve linked to several different retailers below for your convenience. I encourage you to shop around as I’ve found that each item may sell for less at a different retailer.

Supplies

QUIKRETE Countertop Mix


Melamine Plywood

  • The Home Depot
  • I used 4×8 sheets. You may need to special order or visit your local store.

Polyblend Non-Sanded Grout


DAP Silicone Caulk


3/8 in. Rebar


Grip-Rite Rebar Ties


Power Pro 3″ Exterior Screws


Grip-Rite 2″ Exterior Screws


Plastic Sheeting


FrogTape


Furniture Safety Strap

Personal Protective Equipment

Firm Grip Flex Impact Gloves


Firm Grip Nitrile Gloves


RZ Mask Dust Mask


3M Safety Glasses


3M Earmuff


Related Article: PPE: DIYers Should Use Personal Protective Equipment

*Cannot be combined with other promo codes. Can only be used one time, per person.

Steps

How To Make Concrete Countertops

  1. Measure for the total countertop square footage.

    I have linked to the QUIKRETE concrete calculator so you can determine how many bags of concrete you will need.

  2. Build the concrete forms using melamine plywood.

  3. Seal the concrete forms with silicone.

    I recommend using DAP acrylic latex plus silicone caulk.

  4. Build the rebar inserts.

    Including rebar is optional but recommended.

  5. Mix the concrete.

    Follow the mixing instructions closely.

  6. Pour the concrete mix into the form at half the depth of the finished countertop.

  7. Vibrate the mix by tapping the outside of the form with a rubber mallet or placing an electric sander without a sanding pad against the sides of the form to consolidate the concrete.

  8. Allow the concrete mix to get ?thump print hard? and place the rebar on top.

  9. Wrap strands of flexible metal wire around various points of the rebar and hang off the edge of the form to prevent movement.

  10. Allow the concrete mix with rebar to harden for 6-8 hours before removing the strands of metal wire and pouring the second layer (which will be the second inch in the final two-inch thick concrete countertop).

  11. Vibrate the mix by tapping the outside of the form with a rubber mallet or placing an electric sander without a sanding pad against the sides of the form to consolidate the concrete.

  12. Screed the surface.

  13. Smooth the surface with a finishing trowel.

  14. Cover with plastic and leave undisturbed for at least 18 hours before stripping the forms.

  15. Carefully flip the slab over.

  16. Fill any holes on the surface and the sides that were caused by trapped air bubbles.

    I recommend using Polyblend Delorean Gray Non-Sanded Grout.

  17. Once the grout dries, sand the surface with 120 grit sandpaper.

  18. Repeat steps 16 and 17 as necessary.

  19. Set the countertop sections into place.

  20. Caulk seams and seal the concrete.

QUIKRETE Countertop Mix

Quikrete Countertop Mix

QUIKRETE Countertop Mix is a specially formulated flowable high-strength concrete mix for pre-cast and cast-in-place concrete countertop applications.

  • Super-plasticizer additive provides a flowable mix at low water/cement ratio.
  • High-flow formula minimizes the need for mechanical vibration.
  • Reduced-shrinkage formulation.

Concrete Countertops: Planning and Special Considerations

Concrete Countertops Specs

Planning

Like all projects that involve square footage, to begin you should measure the square footage of your countertops to determine how much concrete you’ll need.

  • Pro Tip: QUIKRETE has a concrete calculator that you can use to determine how many bags of Countertop Mix you’ll need for your project. Because their concrete calculator is for a 4″ slab, simply reduce the amount of 80-pound bags needed in half because for this project you’ll be pouring 2″ slabs. You might want to plan for a bit extra to allow for waste.

You’ll also need to consider how your sink and faucet will factor into this project. I installed an apron-front farmhouse sink that lies underneath the concrete countertops (article coming soon), so I simply built a melamine form in a u-shape that matched the sink.

For sinks that lay on top of the countertop, you’ll need to attach foam board in the size and shape of your sink to the concrete form. The foam will create a void in the concrete and will allow you to install the sink.

A void(s) will need to be created for the faucet as well.

Pre-cast vs. Cast-In-Place

This tutorial explains how to pre-cast concrete slab sections that will have to be set into place. There is also the option to pour into a fixed form in your kitchen. There are advantages and disadvantages to both.

Pouring sections that you set in place will allow you to do the messy work outside. Between the wet concrete and the dust that’s kicked up from finishing, this project can create a mess that you won’t want inside your house. On the other hand, pouring in sections will require seams. You may not want the look of seams in your countertop surface.

Another advantage of pouring in sections is that when you pour the concrete onto the melamine board, the side of the cured concrete that faces the board becomes a smooth, finished surface that will be the top of your concrete countertops. I added a layer of grout to fill in voids created by air bubbles, but to me that’s much easier than trying to trowel to perfection and sand a more difficult cured surface to achieve the desired results.

Pouring into place in your kitchen will remove the appearance of seams. But you will have to deal with a mess and a considerable amount of finishing work to achieve a smooth surface.

Weight

Not to state the obvious, but concrete is very heavy! Not only will you have to deal with handling the 80-pound bags, but once dry, the concrete slabs will require at least two people to move (maybe more).

You should give consideration to how the weight of the concrete will affect everything underneath it. You may want to add bracing to your base cabinets. If your house has a crawlspace, you may also want to add bracing underneath the floors as well. While I won’t say if you need bracing or not, it is something you should think about before starting this project.

Rebar Shadowing or “Ghosting”

Rebar shadowing is when you can see the rebar lines in the finished top. There are several reasons why this can occur and also ways to minimize it. You can read more about this further in this article.

Building Concrete Forms

  • Concrete Countertops Forms
  • Concrete Countertops Forms
  • Concrete Countertops Forms
  • Concrete Countertops Forms

Melamine is an excellent material to use for the concrete forms. The concrete won’t stick to the white finished surface, which allows for easy disassembly after the concrete cures.

I used a circular Saw with a Diablo 7-1/4 in. fine saw blade to cut the melamine.

When measuring for the bottom form that the concrete will lay on, add 1 1/2″ (3/4″ x2) to the length and width of your overall concrete countertop measurement. This extra 1 1/2″ is for the width of the form side walls. For example, if your concrete slab is 26″ x 70″, your bottom melamine board should be 27 1/2″ x 71 1/2″.

Your sidewalls should be 2″ in width (they’ll stand 2″ in height on their sides). Be sure to cut them as straight as you can to avoid a varying thickness in the concrete.

To attach the sidewalls to the bottom board, drill a pilot hole, use a larger drill bit to countersink the hole, then use 2-1/2 in. exterior screws every 6-8 inches to attach the sidewalls (see photos above). Countersinking the holes will allow the screws to sit flush and this is important for two reasons. One, this will help avoid splitting the wood, and two, you won’t hit screw heads when you screed the concrete surface.

Sealing The Forms

Once the sidewalls are fastened in place, cover them with FrogTape. Screeding may pull some of the tape up but for the most part the tape will help shield the concrete from getting on the screw heads.

Apply DAP silicone caulk to all the inside seams. I used my finger to lightly smooth the caulk and removed any excess. You may need to apply a second bead once the first dries to build up the layer of caulk. Caulk seals the inside of the form and provides a rounded edge to the top of the concrete slabs (it won’t stick to the cured concrete).

I’ve seen tutorials that recommend using painter’s tape around the seams before applying the caulk but that just didn’t work for me.

If you plan to use 3/8 in. rebar, now would be a great time to grab your angle grinder and make your cuts. I also used rebar ties to hold the rebar pattern together (see photo above). Once your pattern is built, set the rebar aside because you won’t be adding it at the moment.

The last step here is to clean out the inside of the form to remove any dust and foreign materials.

Mixing Concrete

Quikrete Concrete Countertops

Mixing concrete may seem intimidating, but as long as you pay attention to how much water you’re using, you should do great! QUIKRETE has made the water ratio pretty simple: Add approximately one gallon of water to one 80lb bag of mix.

Whether you buy or rent, a concrete mixer is probably the easiest way to go for this job. Because I already had the tools on hand, I decided to mix my concrete in a 5-gallon bucket.

I found out, though, that a bucket isn’t large enough to take an entire bag of mix along with the amount of water needed. For each mix, I poured in about 3/4 of a bag of mix and added water accordingly. Using a Leaktite mix bucket is essential for determining how much water you’re adding to the mix.

I used a corded drill with a mixing paddle to mix the concrete. Be sure to wear a RZ Mask dust mask and nitrile gloves during the mixing process.

Official QUIKRETE Mixing Instructions

  • Link To PDF | “For each 80 lb (36.3 Kg) bag of Countertop Mix to be mixed, add approximately 1 gallon (3.8 L) of fresh water to the mixer. Turn on the mixer and begin adding the bags of concrete. If the material becomes too difficult to mix, add water sparingly until a flowable mix is obtained. Machine-mix for a minimum of three minutes after the final water addition. The recommended slump is 5″ – 7″ (127-178 mm). Do not exceed recommended slump range. Note: Final water content should be 8-9 pints (3.8 ? 4.3 L) per 80 lb (36.3 Kg) bag.For a decorative look, glass or colored stone can be added to the mixture. Do not add more than 20 lb (9 Kg) of glass or stone per 80 lb (36.3 Kg) bag.”

Pouring and Finishing

  • Pouring Concrete Countertops
  • Concrete Countertops Adding Rebar
  • Screeding Concrete Countertops
  • Finishing Concrete Countertops

When I started this project, I was unaware of the issue of rebar shadowing or ghosting. My slabs all have faint shadows that show where the rebar lies underneath the surface. I’m not thrilled about this, but it is what it is. We love the overall look of our countertops and can overlook the lines.

Instead of sharing how I filled my forms and set rebar, which clearly lead to rebar shadowing, I’m going to share some tips from the pros. I asked QUIKRETE directly about this issue and they gave some steps to minimize it.

How To Minimize Rebar Shadowing

  • Follow the directions on the bag for mixing the QUIKRETE Countertop Mix to the right consistency.
  • Pour the concrete mix into the form at half the depth of the finished countertop. So, for a two inch countertop, pour one inch of concrete mix into the form.
  • Vibrate the mix by tapping the outside of the form with a rubber mallet or placing an electric sander without a sanding pad against the sides of the form to consolidate the concrete.
  • Allow the concrete mix to get “thumb print hard” and place the rebar on top. Then wrap strands of flexible metal wire around various points of the rebar and hang off the edge of the form to prevent movement.
  • Allow the concrete mix with rebar to harden for 6-8 hours before removing the strands of metal wire and pouring the second layer (which will be the second inch in the final two-inch thick concrete countertop).
  • Vibrate the mix by tapping the outside of the form with a rubber mallet or placing an electric sander without a sanding pad against the sides of the form to consolidate the concrete.
  • Leave undisturbed for 18 hours before stripping the forms.

Finishing

After I poured all the concrete into my forms, I used a 2×4 to screed the surface, then used a finishing trowel to smooth it nice and neat. Even though this surface will actually be the underside of the countertop, it’s still good to get it as smooth as you can to minimize leveling issues when you go to set it in place.

Once the surface is smoothed, cover it in plastic sheeting (don’t allow the plastic to touch the surface) and let the slab sit undisturbed for at least 18 hours. I gave mine a little extra time and let them sit for 24 hours.

After the initial curing period you can uncover the slab and remove the 2″ melamine form walls. Watch me do this on Instagram.

After you remove the walls, with assistance, carefully flip the slab over (it should easily separate from the bottom board). At this point I again covered the slab in plastic and let it cure until the following day.

The finished surface will likely have holes that were caused by trapped air bubbles during the pouring process. To fill these, I used Polyblend Delorean Gray non-sanded grout. We really like this grout color and the extra character that the filled holes provide in our concrete countertops.

Other than having to repeat the grouting process a few times in order to completely fill the holes and having to sand the surface (120 grit), I followed the instructions listed on the grout package and am pleased with the results.

Setting The Concrete Countertops

DIY Concrete Countertops

This is the exciting part! Be sure to get some help to move your concrete slabs; they are very heavy.

(Stay Tuned: This article will be updated once we seal the concrete and caulk the seams)

Please feel free to share your tips for making concrete countertops by leaving a comment below.

4 thoughts on “How To Make Concrete Countertops”

  1. I have been thinking that it would be smart for me to try installing concrete countertops in my kitchen and my main floor powder room this year. Mainly because it looks really modern and would go with the rest of my house design. Thanks for explaining that I will need to put rebar in the middle of the concrete to help give it something to grab onto and be more stable.

  2. I liked how you mentioned that you can pour concrete into sections so you can do messy work outside. My wife and I are wanting to renovate our house and we were wondering how we can pour concrete without making a mess. I’ll be sure to tell her that we should pour the concrete into sections so we can keep it outside.

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