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How To Install An Undermount Sink

August 14, 2020

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Our master bathroom renovation was full of firsts for me – my first real demo, my first time tiling, and my first time installing a new vanity/sink/faucet. All the other sinks in our house have drop-in style sinks that sit on the countertop, and while those are fine, my heart has always loved the look of undermount sinks. So when it came time to pick a new vanity, one that came with an undermount sink was on my priority list.

Our new vanity came as a set with a marble countertop and an undermount sink. However, all three of these pieces arrived in separate packages, so I would have to put them together. This separation made the install of the sink super easy for me. Hubby and I flipped the countertop upside down and I installed the sink from the top side. So easy. But . . . my success was short lived. Just a few weeks later, as I was working on installing our new sconce lights, I dropped a heavy tool and it landed right in the sink, taking a huge chunk of the porcelain with it! I know that every project has it’s snags, but Man! It felt like we were running into a lot of them! There was lots of yelling and swearing, but once I calmed down, it was time to fix the problem. I hopped on the computer, ordered a new sink, and waited for it to arrive.

Since the countertop had now been installed onto the vanity, I couldn’t take the easy route for installation this time. I needed to install the sink from below. Despite my nerves, this was actually surprisingly easy. You just need the right supplies and an extra pair of hands. For supplies, you’ll need:

  • Scrap wood, cut to the height between the vanity and the sink bottom
  • Tube of adhesive (I used Loctite PL 530 since it’s made for marble countertops like ours)
  • Shims
  • Mallet
  • Towel or rag (to prevent scratching the vanity)

When it was time for install, I applied a liberal bead of adhesive to the edges of the sink. Then, from underneath, I lifted the sink up until my husband could grab it (via the open drain hole) and position it correctly. While he held it, I gently moved my piece of wood into a vertical position between the sink and the vanity. I used a mallet to gently tap it into place. If you find your board is coming up a little short, add shims until it sits snuggly between the two surfaces.

The board is what holds the sink in place until the adhesive has time to really harden/cure. How long that takes will depend on the type of adhesive you used. I left the board there for a day or two just for good measure.

After the board is in place, it’s time to (carefully) crawl under the sink and install the clips that help hold the sink in place (these should have come with your countertop). It’s just a few little Z-ish shaped pieces of metal, with wing nuts. Thread the bolt through the one side of the clip’s lip, making sure that the opposite lip sits under the lip of the sink, “holding” it in place. Repeat this step for all remaining sink clips.

All that’s left to do is wait for it to dry and re-hook up the plumbing and fixtures.

This whole process took me maybe 20 minutes. I was super nervous about it because I’d never done it before and it seemed so hard. It just goes to show that just because a project or tasks seems scary or hard, doesn’t mean it actually is. Now I can add another DIY skill to my tool belt!

1 Comments

  • Demi

    August 18, 2020 at 10:03 PM

    Oh wow! I did not know how much goes into installing an undermount sink. Who knew! This will be useful for when I buy a house, haha.

    Demi | https://demibang.com/

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