How To Install A Kitchen Undermount Sink

Undermount kitchen sinks create a beautiful, seamless appearance in any kitchen. Since they don’t rest on your countertop, they free up a few extra inches of precious counter space, giving you plenty of room to work.

On top of their sleek appearance, undermount sinks are easy to clean and maintain, making them the perfect fit for busy kitchens.

Key Points:

  • Undermount kitchen sinks create a seamless appearance, freeing up counter space and allowing for easier cleaning.
  • Professionals usually charge between $350-$1,500 to install an undermount kitchen sink; however, the cost may vary.
  • When installing an undermount kitchen sink, consider what type of reveal (positive, zero, or negative) you want and gather the necessary material beforehand.

However, while they’re an ideal fit for countless kitchens, the installation process can be somewhat tricky. The sink needs to be firmly secured to the underside of the countertop to avoid mishaps, and if you don’t know what you’re doing, achieving this can be challenging.

But, lucky for you, we’re here to help.

Here’s what you need to know about installing an undermount kitchen sink.

Can I Install An Undermount Sink Myself?

Installing an undermount kitchen sink yourself is doable but might be complicated for some folks. While the project isn’t overly challenging, securing the sink to the underside of the countertop adds an extra element of complexity.

So, while you can DIY the project, it might be better to have a professional handle it if you’re inexperienced with these projects.

Most homeowners pay between $350 and $1,500 to have a professional install their undermount sinks, but your project may cost more or less based on factors specific to the installation.

Are Undermount Sinks Difficult To Install?

Undermount sinks are somewhat challenging to install compared to their popular drop-in competition. They’re not a good fit for all types of countertops, making them a bit trickier to work with than a drop-in sink.

Installing these sinks requires intermediate skills, so if you’re an experienced DIYer (with plumbing projects), you shouldn’t have any issues.

Do You Install An Undermount Sink Before Or After The Countertop?

For the most part, it’s easier to attach the undermount sink to the countertop before installing it over the base cabinets. This way, you don’t need to contort yourself to get a good angle for securing the clips to the underside of the installed countertop.

However, the order will vary based on the scenario. For example, if you’re pouring concrete countertops, the sink usually needs to go in first. Conversely, if you’re replacing an old sink, it doesn’t make sense to tear out the countertops just to replace the sink.

In this case, you’d probably be better off working with the installed countertop, as removing it is unnecessary.

What Holds An Undermount Sink In Place?

The attachment system with an undermount sink varies based on the model you choose. Some sinks come with two-part epoxy adhesive, which firmly attaches the sink to the underside of the countertop. A layer of silicone caulking is added after securing the sink to create a watertight seal around the perimeter.

On the flip side, other sinks have clips or metal anchors that add an extra layer of security. The clips or anchors are often used with a two-part epoxy or caulk for the best results.

How Do You Install An Undermount Kitchen Sink?

Here is a quick video before we get started that may help:

Pick A Reveal

First, you’ll need to decide what type of reveal you want: positive, zero, or negative. A positive reveal offsets the sink and countertop edge, exposing the sink’s rim.

A zero reveal ensures the edge of the countertop is flush with the edge of the sink rim, creating a clean line into the sink basin. Negative reveal offsets the sink and countertop edge, creating an overhang of the counter over the sink basin.

Each option has merits, but many homeowners choose a sink with zero reveal, as it’s usually easier to clean. That said, it’s up to you, so pick the option that best matches your preferences.

Gather Your Materials

Before you start the project, you’ll need to gather a few materials. Your materials list will hinge on your particular scenario, as each installation differs. Here’s what you might need:

  • Pencil
  • Circular saw or jigsaw
  • Safety goggles
  • Work gloves
  • Power drill
  • Denatured alcohol
  • Clean rags
  • Construction adhesive or provided glue
  • Sink clips
  • Silicone caulk
  • Adhesive remover
  • Scraper
  • Bar clamps
  • Sandpaper

MENSARJOR Undermount Sink, 27" x 18" Single Bowl Kitchen Sink Undermount Stainless Steel Kitchen Sink, Bar or Prep Kitchen sink

Prepare The Countertop

Once you gather your materials, it’s time to prepare the countertop. If you’re working with a new countertop slab, you’ll need to cut a hole for the sink.

If you’re replacing an old sink, you might need to make minor adjustments to ensure the existing hole matches your new sink, but it’ll depend on the situation.

Many sinks come with cardboard templates to simplify the installation process, so use that to trace the sink hole. However, if your sink didn’t come with a template, simply flip the sink upside down and trace the outline on the countertop with a template.

Remember, the outline will be slightly larger than the sink opening, so make a second outline inside the traced outline. The second outline should be approximately ½-inch smaller than the original on all sides.

If you’re working with an uninstalled countertop, measure twice to ensure the traced section falls in the right spot. Once you’re ready, it’s time to cut the hole.

Use a circular saw or a jigsaw to slice through the countertop, wearing safety goggles and work gloves. Use a power drill to drill extra holes for the faucet or other accessories.

When you’re finished cutting the hole, clean the cutout and surrounding area with denatured alcohol and a clean cloth. You might need to clean up the cutout with a piece of sandpaper, but this will depend on the countertop material you’re working with.

Note: If you’re working with natural stone countertops, you might want to have a professional cut them for you. These countertops are expensive and tough to cut through, as they’re extremely solid, so it’s usually better to have a professional handle this part of the process.

Of course, you can do it yourself, but you’ll likely need special tools to ensure you can complete the job.

Installation: Unattached Countertops

The installation process varies based on the situation, so if you’re working with an unattached countertop, follow these steps. Before you start, ensure you have plenty of clearance on all sides of the countertop.

Next, flip the countertop over, so the underside faces up. Using a pencil, trace the outline of the sink on the bottom of the countertop, then lift the sink and set it aside. Place the mounting clips at each sink corner and one at 10-inch intervals along each side for added stability.

Secure the sink clips with construction adhesive. Give the adhesive plenty of time to dry, ensuring you follow the instructions on the product label. Once the glue dries, apply a thick bead of silicone caulk along the inner edge of the sink’s outline.

Carefully set the sink in place, aligning it to the reveal you prefer. Rotate the wingnuts on the clips to secure the sink to the countertop. Clean up excess caulk oozing from the sink with a clean cloth and denatured alcohol.

Give the caulk 24 hours to dry completely (or the manufacturer’s recommended dry time) before turning the countertop over. Flip the countertop over and clean up the excess caulk with a utility knife, a clean cloth, and denatured alcohol.

Install the countertop in its place, securing it to the base cabinets.

Installation: Attached Countertops

The process looks a bit different if you’re working with an installed countertop. While it’s easier to install an undermount sink on an uninstalled countertop, removing an existing countertop to install the sink is an unnecessary step.

You can install the sink on an existing countertop, but you’ll have to work within the confines of your kitchen sink base cabinet. Ideal? No. Doable? Absolutely.

To start, you’ll need to turn off the water supply to the existing sink (if applicable). Turn off the water at the shut-off valves beneath the sink, then drain the excess water from the lines by turning on the faucet and letting it run.

Once the water stops flowing, turn the tap off. Disconnect the faucet and pipe fittings beneath the sink and remove the garbage disposal (if applicable).

Remove the old sink and carefully lift it out of its place. Remove the old adhesive from the countertop using an adhesive remover and a scraper. Ensure the underside of the countertop is free of old adhesive, as it can interfere with the seal between the countertop and the new sink.

If you’re using sink clips, install them now. Place them at the corners of where the sink will go and at 10-inch intervals along the sides. Set up a support system for the sink, like 2-by-4-inch boards, as you don’t have gravity working in your favor. The sink will need to rest on something as the caulk or adhesive dries.

Apply a thick bead of caulk along the inside of the countertop where the sink rim will sit. Raise the sink into position and press it firmly against the caulked area, aligning it as necessary to match your reveal preferences.

Use shims and extra board to create a snug, stable platform for the sink to rest on as it dries. You can also use bar clamps to secure the sink to the countertop as it dries. Rotate the wingnuts of the clips into place to further secure the sink to the countertop. Leave the support system under the sink while it dries.

Wipe the excess silicone around the sink using a clean cloth and denatured alcohol. Once you clean up your workspace, let the caulk dry for 24 hours or to the manufacturer’s instructions.

You can remove the support system when the caulk is dry, and the sink is secure. Slide out extra shims and boards, then gently lift the supports out of the base cabinet.

Install Faucet And Drain

Once the caulk is dry and the sink is securely fixed to the countertop, it’s time to complete the project. Install the faucet in the prepared holes in the sink deck or countertop, following the installation instructions provided by the manufacturer. Install any accessories, like soap dispensers or sprayers.

Install the sink drain and hook it up to the plumbing beneath the sink. Connect the faucet to the water supply lines, then turn on the water at the shut-off valves beneath your sink (if applicable).

Check Your Handiwork

Your last step is to check your handiwork. Turn on the water at the faucet and check for leaks around the drain and plumbing underneath. For the ultimate test, fill the sink with water, open the drain, and watch for leaks.

If you find leaks, adjust the plumbing or setup as necessary to correct the problem. If everything is watertight and snug, congratulations, you installed your undermount kitchen sink!

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