How to Attach an Undermount Sink to a Granite Countertop in 8 Steps

Undermount sinks paired with an eye-catching granite countertop create a classic look that you’ll love for years to come. These sinks make for easy kitchen cleanup, and their design suits a variety of aesthetics.

Some homeowners may shy away from granite undermount sink installation because they believe the process is more complicated than other types of sinks. In reality, with a few additional steps and the right tools, installing an undermount sink is possible on your own. When the project is finished, you’ll be happy you went through the extra effort.

What Is an Undermount Sink?

As their name suggests, undermount sinks sit beneath the surface of your countertop. There aren’t any pre-cut holes in which the sink will sit, but instead, the edge of the sink will sit slightly under the counter.

Undermount Sink Materials

Undermount sinks come in a variety of materials, including:

• Stainless steel
• Copper
• Granite composite
• Quartz composite
• Cast iron
• Fireclay
• Matte stone
• Acrylic

And so many more. Make sure to do your research to see which material will best suit your aesthetic and functional needs.

Undermount Sink Benefits

You may be wondering why you should consider installing an undermount sink. There are two main benefits that you may not have considered.

First, cleaning your countertops is significantly easier when you have an undermount sink. Food particles, dust, and other crumbs can easily be directed into the sink without spilling onto the floor first. If your kitchen is a particularly high-traffic area, this is especially beneficial to help you save time during clean up.

Secondly, undermount sinks are deeper than traditional sinks. Standard sinks are roughly 5 inches deep, while undermount sinks have nearly 10 inches of space. This makes it significantly easier to wash dishes, prepare meals, and stay organized.

Mounting your undermount sink to granite is one of the easiest ways to maximize your kitchen’s functionality while still adding to its modern appeal. Plus, if you don’t have granite countertops, you can still install an undermount sink with nearly any type of stone countertop.

How to Install an Undermount Sink on a Granite Countertop

If you’re ready to transform your kitchen sink, you’ll first need to prepare by gathering the right tools. Doing so will set you up for success!

Tools and Materials You Need

Of course, you’ll need a sink in order for this project to be a success. In addition to your new sink, compile the following tools before you get started:

• The correct mounting hardware for your sink
• Power drill
• Tape measure
• Screwdriver
• Clamps
• Silicone sealant

From there, you’ll be ready to get started! Follow these steps carefully for granite undermount sink installation.

Step #1: Measure the Hole

You’ll first need to make sure that you have the right size hole for your new sink. Typically, most sinks are 33×22 inches from outside rim to outside rim. If your current sink’s hole is this size, you are ready to continue the rest of your project.

If you need a new hole entirely, we recommend relying on a professional. The last thing you want is to cut a hole in your granite that isn’t the correct size. This would be an expensive mistake!

Step #2: Choose the Reveal Style

The “reveal style” refers to how much of your sink’s rim will show when the installation is complete. There are three different reveal styles from which you can choose:

• Positive reveal: In this type of undermount sink, a portion of the sink is visible. The countertop sits just far away enough from the edge of the sink that there’s a small portion of the sink that shows.
• Negative reveal: This type of design features a countertop that extends over the edge of the sink, making the sink completely invisible.
• Zero reveal: Also referred to as a flush mount, zero reveal sinks feature a countertop that sits flush against the inside of the sink. Of the three types of sink reveal styles, this is the most difficult and complicated to install.

The reveal style that you ultimately choose comes down to your personal preference. The majority of homeowners opt for zero reveal sinks because not only does it look clean and professional, but it also minimizes space for dirt and grime to compile.

Step #3: Measure & Mark

Use the opening to guide your sink into place, carefully centering it as you set it into the proper position. If you are opting for a zero reveal sink, make sure that the rim of the sink is aligned on the edges.

Lightly mark on the countertop where you’ll need to drill holes and take the sink out. Remember, always measure twice and drill once; you’ll want to triple-check that you measured and marked the correct holes.

Once the holes are marked, take denatured alcohol to clean the ridge and allow it to dry before moving onto the next step completely.

Step #4: Add Sealant

Next, take your sealant and add a thin layer to the sink lip, and put the sink in from underneath. Make sure it is sitting on the granite how it’s supposed to. From there, you can add caulking to seal the sink in place.

We recommend using clear caulking as it allows you to see exactly where you are working. This is especially beneficial if your granite is dark-colored.

Step #5: Insert the Wingnuts

Use wingnuts to secure the sink into place, ensuring that the nuts are tight and won’t budge. At this point in the project, you’ll want to give the sink a few days to set before moving onto the next step.

Step #6: Attach to Plumbing Lines

After a couple of days have passed, use the manufacturer’s instructions to attach the sink to plumbing. You’ll also want to thoroughly caulk around the seams to make sure they’re sealed and waterproofed.

Step #7: Check Your Work

There’s no such thing as being overly cautious! Use your hands to apply extra pressure to the top of the sink to make sure it can withstand it. You can press out trapped air with your hands.

Step #8: Wipe Away Excess Material

Once you’ve pressure tested the sink, take a damp cloth and wipe away any excess sealant or caulk. Step back and enjoy your work!

Undermount Sink Maintenance

Now that you’ve mounted your sink to your granite countertops make sure to do your due diligence to keep it clean and damage-free. The reveal type that you chose will play a factor in how you care for your sink.

Negative reveal sinks expose the underside of the countertop to water, potentially causing damage to the granite over time. The moisture could seep into the porous material and become a breeding ground for bacteria and mold. Make sure to fully seal the granite before you use your sink to protect it from long-term damage.

You should also be mindful of the space between your granite and the sink, as this is a nearly impossible gap to close regardless of the type of reveal you chose. As a solution, take silicone caulk and fill the gap to prevent bacteria buildup.

As a general rule of thumb, recaulk your sink every 3-5 years to help extend your undermount sink lifespan. With the right care and attention to detail, your undermount sink installation can last a lifetime!

Conclusion

In the case that you don’t feel confident mounting your undermount sink to your granite countertops on your own, call our experts instead. At Pro Stone Countertops, our team has decades of experience, and we’re dedicated to helping our clients achieve unmatched results.

To get a quote on your specific undermount sink installation project, get in touch with our team today!