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How To Install An Undermount Sink In 9 Steps


How To Install A Bathroom Vanity in 12 Steps
A popular trend in bathroom design is an undermount sink that offers a sleek and modern feel. This sink type features a distinctive look with the edge of the sink mounted below the countertop, creating a continuous flow from the countertop into the basin.

Besides its streamlined appearance, homeowners enjoy this style because it makes cleaning much easier. Since the edge of the sink is hidden below the vanity top instead of sitting on top of the counter, the lack of a lip makes the edges less likely to catch dirt.

An undermount sink can also have a positive, negative, or zero reveal. A positive reveal is where the countertop edge sits back from the edge of the sink and a small portion of the sink rim is exposed. A negative reveal is when the countertop extends slightly over the top edge of the sink on all sides. A zero reveal is when the sink and the countertop align perfectly flush on top of each other. These options give you more flexibility to better customize your look.

Undermount sinks are best suited for solid surface countertop materials like granite or marble. They are less suited for laminate or tile countertops, which have too many weak points along seams and grout lines to support the weight of the sink.

You can install an undermount sink to add a sleek, fresh feel to your bathroom, plus it's a simple way to upgrade the space. They also provide slightly more counter space and storage so items used daily are readily available.


Soft Cloth
Soft Cloth
Mineral Spirits
Mineral Spirits
Silicone Sealant
Silicone Sealant*


Mineral Spirits
Mineral Spirits
Denatured Alcohol
Denatured Alcohol
Silicone Sealant
Silicone Sealant*


Installing an undermount sink in your bathroom can take up to 30 minutes or less with the correct tools and materials at hand. If it’s your first time taking on this type of project, it can take longer depending on how many people are assisting. Make sure that the bathroom is not essential the day you decide to complete the installation, so there is less foot traffic and interruptions.

9 Steps to Install an Undermount Sink


 Step 1: Shut Off Water Supply

  Illustrated image of water supply valve Make sure that the water supply has been shut off and the plumbing fixtures have been disconnected before you begin to install the undermount sink.  

 Step 2: Flip the Vanity Top Upside Down On a Soft Surface

  Illustration of a black vanity top with a sink cutout on a blue surface Carefully turn the vanity top over so that it rests upside down on a stable, cushioned surface. One of the differences between an undermount sink and a standard drop-in sink is that the cutout must be cut precisely to match the sink dimensions.

Smooth the edges of the hole with sandpaper so it won't damage the sink. Clean the dust from the vanity top and the opening with a clean cloth and denatured alcohol. Be sure to allow the surface material to dry completely after cleaning for the adhesive to be able to work properly.

 Step 3: Position Sink Over the Sink Cutout

  Illustration of a black vanity top and sink cutout with gray undermount sink flipped over on a blue surface Position the undermount sink over the cutout on the vanity top. Make sure the sink is centered with the faucet hole and is evenly spaced between the bolt holes. Ensuring it’s correctly aligned is critical before moving to the next step.  

 Step 4: Draw an Outline of the Sink on the Vanity Top

  Illustration of a black vanity top with gray undermount sink flipped over on blue surface and hand holding pencil drawing an outline Using a pencil, draw an outline of the sink on the vanity top, once the ideal position is determined.  

 Step 5: Remove Sink and Apply Silicone

  Illustration of a gray undermount sink flipped upright and a hand holding silicone After tracing the outline, remove the sink from the vanity top. With the sink flipped upright, apply a generous bead of silicone to the perimeter of the sink’s rim. Ensure the bead of silicone is a uniform amount all around.

Note: Copper sinks use a Neutral Cure Silicone Sealant*

Use denatured alcohol again to clean the edge around the sink hole where the sink will be positioned. This will remove any grime to ensure proper bonding with the silicone.

 Step 6: Place Sink Upside Down on Outline

  Illustration of a black vanity top with a gray undermount sink flipped over on a blue surface with two hands pressing down on the sink Carefully place the sink upside down on the vanity top cutout, positioning it within the outline that was previously traced.

Press the sink firmly to ensure the proper spreading of the silicone. The weight of the sink should push against the vanity top, but if it’s very light, consider using a weight or another person to help press it down.

While one person raises the sink up and places it on the vanity top, the second person should make sure it’s positioned properly.

 Step 7: Attach Sink Clips and Wing Bolts

  Illustration of a black vanity top and a gray undermount sink flipped over on a blue surface with a hand attaching bolts Attach the sink clips (if included) by placing the long end of the bracket flat against the sink lip. Screw the wing bolts through the brackets and bolt holes and tighten snugly.

Before you tighten the sink clips, adjust the position of the sink. You want to do this before the silicone sets, so you have the opportunity to make it align perfectly with the cutout in the vanity top.

 Step 8: Carefully Flip Vanity Top

  Illustration of a black vanity top with a gray undermount sink flipped upright After the silicone has fully dried, carefully turn the vanity top and attached sink over. Make sure there aren’t any gaps between the undermount sink and the vanity top. If you notice a gap, the sink clips may not be tight enough.  

 Step 9: Remove Excess Silicone

  Illustration of a black vanity top with a gray undermount sink flipped upright and a hand wiping the sink with a cloth As you push the sink against the countertop, it may cause some of the silicone to squeeze out. Wipe it up right away to prevent it from hardening. Remove any excess silicone with a cloth moistened with water or mineral spirits. Let the silicone dry according to the manufacturer’s instructions.

You may have to wait for up to 24 hours for adequate drying of the silicone before proceeding to install other fittings, such as the faucet.

Watch Our Video About Installing an Undermount Sink

For further instruction, follow along with this how-to video on installing an undermount sink. It’s important to not miss even the smallest of details throughout the installation process. To ensure the renovation goes smoothly, look to our video tutorial for additional tips and guidance.

Hi, I’m Tom from Signature Hardware. Today I’m going to show you how to attach an undermount sink to a stone countertop.

For demonstration purposes, I am going to be resting the countertop on one of our console sink stands.

We’re going to need a couple of tools for the job; a large towel, a pencil, silicone sealant and a damp cloth.

Carefully turn the countertop over so that it rests upside down on your towel.

Position the sink over the sink cutout on the counter. Make sure the sink is centered with the faucet hole and is evenly spaced between the bolt holes.

Once the ideal position is determined, trace an outline of the sink on the countertop.

Lift the sink from the countertop and apply a bead of silicone around the rim.

Carefully place the sink upside down on the countertop, positioning it within the outline.

Attach the sink clips and wing bolts and tighten snugly.

Carefully lift and place the counter on the sink stand.

If you need to reposition the sink, loosen the wing bolts, adjust the sink and retighten the bolts.

Remove any excess silicone with your damp cloth.

Allow the silicone to dry for 24 hours.

That’s it! Your undermount sink installation is complete.

To see more of our bathroom sinks and vanities and get answers to any additional questions visit us at signaturehardware.com, or call customer service at 1-866-855-2284.


Complete the Look

  Once your undermount sink is installed, finish your look with a new bathroom faucet. Shop our wide selection of bathroom faucets to find the perfect final touch for your guest or primary bath. Explore all of your options by reading our Bathroom Sink Faucet Buying Guide, with our entire collection in one place. Shop additional bathroom hardware and accents to complete the renovation, such as a matching medicine cabinet or mirror. As all of these elements pull your look together, an undermount sink will be the focal point and a lasting feature in your powder room.  

For more ideas and inspiration, check out these articles