How To Install Undermount Kitchen Sinks

A botched installation can ruin even the highest quality countertop. Today let’s take a look at how to install an undermount kitchen sink with a focus on properly supporting the weight of the sink. Small bathroom or bar sinks are easier – they typically can be mounted directly to the concrete using the hardware provided with the sink. Kitchen sinks are too heavy to mount directly to the concrete, so special preparations must be made.

Order of Installation

It’s very important to install an undermount kitchen sink before the countertop slabs are set down. Once the countertop slabs are set down, you usually will not be able to fit the sink through the hole, and you won’t be able to properly seal between the sink and the underside of the countertop.

  1. First install the sink supports. We’ll talk about 3 different ways to install sink supports below.
  2. Then set the sink onto the support frame.
  3. Apply a generous bead of caulk around the top of the sink’s flange. Use silicone or siliconized acrylic kitchen and bath caulk.
  4. Install the adjacent countertop slabs over the sink, sandwiching it between the countertop and the cabinet frame.

Types of Sink Supports

For concrete countertops, the concrete should not bear the weight of the sink. Instead, you build a support out of plywood, and the cabinet frame together with the support bear the weight of the sink.

Commercial Bracket

The first type of support is a commercial sink bracket sold by granite supply companies. These brackets are designed to be installed onto the cabinet frame. Follow the manufacturer’s instructions.Commercial undermount sink Bracket

Custom Wood Frame

The second type of support is a custom made wood frame that mounts to the cabinet walls. The frame supports the sink by its flanges. Always leave some wiggle room between the sink bowl and the cradle so that you can align the sink with the countertop hole.brackets for undermount sink undermount sink installed on brackets

Custom Plywood Shelf

The third type of support is a sheet of ¾” plywood shelf (yellow, below) that’s cut to fit inside the cabinet. The plywood has a hole cut into it that the undermount sink drops into. The hole in the plywood must be large enough to allow for the sink to be moved to align it with the hole in the countertop. Sometimes it’s useful to rout a roundover along the inside edge of the hole. In addition, it’s important to cut holes for all the plumbing and faucet fixtures that mount to the countertop. The hole in the plywood must be large enough to allow for tools to access the faucet and plumbing hardware.Custom Plywood Shelf for undermount sink


It is very important to create a watertight seal between the underside of the countertop and the sink. Take care when applying the silicone caulk along the flange of the sink that it is generous enough to create a watertight seal, but not so much that it is messy.

Bare concrete will react with silicone to produce a nasty-looking, oatmeal-like consistency that will ooze out of the sink joint. Therefore, you must seal the underside of your sink openings so that only sealed concrete touches the silicone.

Concrete – The Perfect Reason to Get Your Hands Dirty

After completing his training, CCI student Duncan Susag decided to jump right in and start doing concrete full time. Prior to taking the Ultimate course with us he’d gotten his business license, and shortly after arriving home he started making the preparations to make concrete his main endeavor. Three years later he’s still working with concrete full time and has added a gorgeous Tacoma WA showroom to delight and inspire his clients.

This gorgeous green concrete table doubles as a magazine rack

This gorgeous green concrete table doubles as a magazine rack.

Getting His Hands Dirty and Loving It

Duncan loves getting his hands dirty and being a major part in the creation of each piece he produces. He has part time help at times, but the majority of his work he does alone and likes it that way. When talking about expansion he mentions that he wants to stay small, “With a larger shop you’re managing people, not getting your hands dirty.” He hopes to spend his concrete career elbow deep in concrete, creating art and delighting clients with his work… and with pieces like these, who wouldn’t be delighted?

This beauty of a desk is Duncan's own desk, found in his office. Including his company logo makes this piece extra special.

This beauty of a desk is Duncan’s own desk, found in his office. Including his company logo makes this piece extra special.

Using His Showroom to Inspire and Educate

Duncan has found that one of his biggest challenges is building clientele and educating potential customers about the benefits of concrete. This is one reason why his showroom is such an advantage. Unlike many concrete countertop showrooms, Duncan has chosen to combine retail, ready to own pieces with his countertop samples. Clients can come in and see the possibilities of concrete as they walk through his displays of stunning modern tables and unique artistic pieces. Duncan doesn’t just teach about concrete with words; his showroom is concrete proof of what he can do and how this medium can be used to beautify and accentuate homes and businesses.

Speaking of his showroom Duncan said, “The furnishings and artistic offerings are  my creative outlet… My idea was to create some pieces that  would show the uniqueness and versatility of concrete. Clients often come in to look at color samples and see the full potential of concrete and their mind is officially blown!” Why limit concrete to just countertops?

Wood and concrete combine to create this hardworking table available in Duncan's Tacoma showroom.

Wood and concrete combine to create this hardworking table available in Duncan’s Tacoma showroom.

When he was first getting started he found the slow pace of breaking in to be discouraging, but after talking with other concrete veterans he’s come to realize that time is an essential element for making headway in this field. Now after three years he finally is seeing the results. “I am nearing three years and finally feel like my business is gaining some exposure and traction.”

The slanted storage space beneath this table is perfect for tucking away books and magazines.

The slanted storage space beneath this table is perfect for tucking away books and magazines.

As he was getting started he relied on the skills he learned with CCI. His secret to success is simply listening to the things he was taught and applying them. His training gave him a solid foundation on which to build all aspects of his concrete business: marketing, promotion, and of course the actual concrete construction.

This small table makes quite the impact on display in Duncan's showroom.

This small table makes quite the impact on display in Duncan’s showroom.

Staying Local and Going Green

For Duncan creating concrete countertops isn’t just about creating works of functional art, he also focuses on the environment and his local community. He says, “Concrete countertops and other items we produce are widely considered a green product and environmentally friendly product. I absolutely focus on staying true to that. I have found local resources for very nearly all of the products I use.” In fact, he ships in only scrim and sealer. All of his waste is disposed of locally through a company that recycles concrete, melamine, and foam waste for landfill layering.

Concrete doesn't just make amazing countertops; this side table is pretty special too.

Concrete doesn’t just make amazing countertops; this side table is pretty special too.

Countertops and So Much More

In Duncan’s showroom you won’t just find countertop samples. He also has a passion for creating functional concrete furniture pieces, many of which are his own designs. He’ll see something inspirational in a home magazine made from other mediums and will work to find a way to make something similar in concrete. His gorgeous pieces are available for sale in his showroom, which doubles as a gallery for ready to own concrete pieces. His website, serves as an online gallery and showroom.

Thank you Duncan for sharing your beautiful work with us!

Filling seams in concrete countertops

A few months ago, I wrote an article about installation, and I mentioned in there that you should use flexible caulk for seaming, not rigid epoxy, to allow for stress relief in case of slight movement of the slabs.

The other day, I witnessed a clear illustration of this when I visited a client from over 12 years ago. He was doing some renovations, and wanted me to take a look at “a few minor chips and scuffs”.

The surface had indeed held up very well for over a decade, but the biggest issue I saw when I arrived was that one of the slabs which extended out into a long cantilever over a book shelf had shifted a bit.

concrete slab cantilever

This original installation photo shows the large, irregularly shaped slab with drainboard and cantilever over a bookcase. The left side of the slab extends in the back to the center of the faucet, and in the front about 3 inches in front of the sink. The right side of the slab has a “puzzle piece” seam that zigzags back from the right side of the dishwasher to the right side of the cantilever.

That slab shifted about 1/8 inch towards the back, probably due to settling of the bookcase. The back side of the slab also cantilevers about 12 inches beyond the back of the cabinet, and therefore tends to cause tilting towards the back.

concrete slab shifted

This view from the back of the slab shows how it has shifted back about 1/8 inch.

concrete seam opened

The seam has cracked, not the concrete!

This will be super easy to fix! If I had put rigid epoxy in those seams, however, I would have a real problem on my hands. Instead of opened seams, there would be cracks in the concrete.

The client was still happy enough to serve me smoked salmon, champagne, and homemade lemon cake.


These were the ideal concrete countertop clients. They love their concrete countertops because of the imperfections, and they reported, “Looking at our concrete countertops gives us joy every day,” even 12 years later!

They especially like the curved windowsill that extends behind the farm sink.

curved concrete windowsill

And, believe it or not, they still had their original FormWorks sealer touch-up kit in case of scratches (which they didn’t need to use). Now that’s a piece of history!

touchup kit

touchup kit closeup

The Story Behind The Concrete Countertop Institute

I recently created a video explaining how and why I started The Concrete Countertop Institute. I thought I’d post it here, along with the text of what I said. You can also view this on the About Us page of my website.

Here’s what I said in the video:

I’d like to give you a little insight into what CCI is all about.

I started making concrete countertops back in 1999, when it was virtually unheard-of. All I wanted to do was make concrete countertops for my own kitchen remodel. Lane and I had bought our first house, and it was a 1990s cookie-cutter subdivision house. You know – white cabinets, white laminate countertops, white vinyl floors, white wallpaper with little pink roses – that was the first to go. It was pretty horrid, as you can see. We had grand visions of moving doors, getting new cabinets, etc., then reality set in and we looked at just replacing the floor and redoing the countertops. Those had to be replaced, because the previous owner had cut on them and scratched them, and set a hot pot on them and scorched them.

My neighbor gave me a stack of home improvement magazines to help give us ideas, and in one of those magazines was an article about this guy in California named Buddy Rhodes. That was the first time I’d ever seen concrete that wasn’t gray, and it totally blew me away. To engineers, concrete is just numbers and a utilitarian material, but this concrete was beautiful.

I had no idea how to color concrete, or to polish concrete, or to make concrete look like that. As I researched how to do this, I found very little information. Remember, back then, there were no books, no videos, no products, just anecdotes on a few discussion boards, from people who had tried it for themselves. All of those stories had something in common. “It turned out nice, but it stained”; “it worked, but the color didn’t turn out”; and, “it came out okay, but it cracked.” They all ended in “but”. I certainly didn’t want a countertop that did that, and I knew I had the background and knowledge to do better.

So instead of following the same problematic path, I started from first principles, and applied my engineering knowledge to figure out how to make concrete countertops that didn’t stain or crack, and didn’t require a lot of maintenance. I literally pulled my textbooks off the shelf, created spreadsheets to figure out the mix design and correct reinforcing, and finally, after 8 months, created my first concrete countertop.

In the course of doing all this research, I found that there were a handful of concrete countertop companies in major cities like San Francisco, Chicago, New York, Washington D.C., and Atlanta. I thought, maybe there’s an opportunity for this new, upcoming market. So I set up a website, and lo and behold, a few weeks later, I had my first customer. [In the video, you can see] a picture of my very first paid project.

As early as 2000, contractors started asking me, “How do you make concrete countertops that don’t stain and crack?” I started helping a few contractors one-on-one. Then in October 2001, I was invited to the first concrete countertop summit, hosted by Steve Rosenblatt of Sonoma Cast Stone. There were 8 people there, including Buddy Rhodes and Fu Tung Cheng, and Fu Tung showed us a slide show of his book-to-be.

That book came out in 2002, and then the interest in concrete countertops exploded. More and more contractors were getting into it, with a variety of success and quality levels. I continued to train one-on-one until I saw that I was just never going to make a dent that way. There were too many people getting into this, and too many instances of clients having bad experiences. I was really afraid the concrete countertop industry would be ruined.

So in 2004, I had my first training class, and here’s a class photo from June 24, 2004.
That first class, we created a simple concrete countertop, using an all-sand mix. Over the years, I’ve kept up with the latest products and techniques, and carefully adopted the ones that really made an impact on students’ businesses, such as GFRC.

I’ve also applied rigorous, quantitative testing to products like sealers and admixtures, to determine whether they really worked and solved a business problem for concrete countertop pros. My latest round of testing in June 2014 will determine what the real, quantitative benefits of various new admixtures are.

This has always been my approach – hard data over anecdotal evidence, rigorous testing over casual experience, determining why over just blindly following a recipe or the latest fashion. That is what CCI is all about – learning both the how and the why behind it, so you have a solid foundation of technical knowledge on which to build your creativity.

This continues my original mission, the reason I started CCI: to raise the standard for concrete countertops by helping people succeed at them without having so many problems. As my logo says, I wanted to provide “knowledge, confidence, and success.”
Ten years later, CCI has trained thousands of people. We’ve provided hands-on training to people in all 50 states, Canada, Mexico, many Caribbean islands, Ireland, England, Scotland, Iceland, Finland, Venezuela, South Africa, Saudi Arabia, India, Thailand, South Korea, New Zealand and most recently Australia, plus self-study training to many more countries.

It has been an absolute privilege to meet so many diverse people, and to influence the concrete countertop industry worldwide.

I no longer produce concrete countertops for customers myself. Because I am 100% dedicated to my students, I would rather support them than compete with them. I refer projects to my students, or help students with their projects. By keeping in touch with students all around the world, I see the challenges they face, not just the challenges I faced producing concrete creations in Raleigh, North Carolina.

I am so proud of my students’ successes and all the amazing projects they’ve completed. It has been a privilege to be part of the concrete countertop industry’s growth, and my students’ success.

CCI provides many ways to learn and grow as a concrete countertop maker – from hands-on classes, to self-study videos, to in-depth product information. I hope to provide you with what you need to achieve knowledge, confidence and success at concrete countertops.

Thank you for giving me the opportunity to help you.

Concrete as a Part Time Job… but a Full Time Passion

Juggling is a skill that Peter Cicalo of Hard Life Products in New Jersey has come to perfect. He balances his growing concrete business with a busy career as creative director for an advertising company. After long hours at work he comes home and spends the rest of the night in his garage shop creating the concrete works of art that he loves.

Joining the Family Business

Peter is no stranger to the hard work that comes with construction. His father was a contractor, and Peter grew up on the job site. After jumping in to his career in advertising Peter decided to put his childhood skills to use remodeling a bank owned home in his area that he hoped to buy. He felt concrete countertops would add the perfect flair to this home. The deal eventually fell through, but Peter’s love of concrete was born as he kept exploring the possibilities, creating and selling little things made from concrete on the side.

This modern inspired concrete fire pit is the perfect place to warm up on a chilly New Jersey night.

This modern inspired concrete fire pit is the perfect place to warm up on a chilly New Jersey night.

Then last year he came to The Concrete Countertop Institute and took our Ultimate Course. The skills he learned ignited his passion, fueling him to take the next step and do more with concrete. Currently he juggles his day job and his concrete business, but he plans to expand enough that he can quit his day job and make concrete his primary focus.

“Work is just work, but concrete is something to look forward to.”

Since Peter works full time in advertising, he has to squeeze his concrete work into the evening and weekend hours. He’s turned his garage into a small but full blown concrete shop. Although he’s only been focusing on his part time concrete business for a year, he already has sink displays in two local showrooms. When he shows his work to builders and others, they are amazed at what concrete can do. He is often told, “I didn’t know concrete could look like this.”

Living by the sea provided the inspiration for this conch shell sink that appears in a local showroom.

Living by the sea provided the inspiration for this conch shell sink that appears in a local showroom.

Although he’s short on time, Peter doesn’t mind spending hours working with concrete after a long day in the office. He says, “The day drags on and then I get in the shop and the time just flies.”  He finds himself accidentally staying up way too late without even realizing where the time has gone. Work is just work, but concrete is something to look forward to.

No one would ever guess this stunning sink was concrete if you didn't tell them.

No one would ever guess this stunning sink was concrete if you didn’t tell them.

Digging into the industry, learning about the different methods people are using, and discovering the wealth of information out there continues to expand his skill set. He encourages others trying to juggle work and concrete to research and learn as much as possible. One of his favorite aspects of his training with CCI was learning the “whys” behind common concrete practices. He doesn’t just want to know what to do, but rather why he should or shouldn’t use a certain method. Since he doesn’t have a lot of time to spare, knowledge about concrete is essential for creating each of his artistic masterpieces.

Another beautiful sample sink by Peter Cicalo.

Another beautiful sample sink by Peter Cicalo.

Peter is a perfectionist by nature and finds that surprisingly this translates into stunning work in the shop. Yes, concrete is a messy medium, but with the techniques he’s learned through training and research, he can control the concrete and create functional and beautiful art. He loves knowing that the pieces he makes will be admired and used every day.

A Bright Future

Since his shop is small and he doesn’t have unlimited time to focus on concrete, Peter currently works on smaller scale projects like fire pits, vanity tops, and sinks. Getting started part time and with small projects is a great way to grow your concrete countertop business organically. We certainly see a future filled with concrete possibilities for Peter, as his pieces are truly magnificent.

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