How To Install An Undermount Kitchen Sink?

If you’ve chosen to have an undermount kitchen sink, you can look forward to a seamless finish that maximizes your counter space. When looking at how to install an undermount sink, as its name explains, the sink is installed from below the countertop. To keep an undermount sink in place, the rim is secured down with a silicone adhesive and metal brackets. 

If you’ve decided to get an undermount sink, here’s an overview of the steps needed to install and secure it properly. 

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Before You Start

For obvious reasons, ensure that your countertop is compatible to carry an undermount sink. Undermount sinks work well with granite, quartz, concrete and marble countertops. To be sure, check with your sink supplier and/or a contractor if your chosen undermount sink is compatible with your countertop. 

The next factor you need to consider is the hole your undermount sink will be fitted into. Buy a sink that will fit into your countertops sink hole. If you’re set on a specific sink and it doesn’t fit into your countertop, add or remove from the countertop accordingly. 

Measure correctly as the last thing you want is to be left with a countertop hole that’s too big or too small during the installation process. Measure from the edges of the counter opening. Make sure that the bottom of your undermount sink basin doesn’t go past the outlets. 

Lastly, if there’s a current sink in place, you obviously need to take steps to remove it. Start by turning off the main water valve, disconnecting the water lines and the drain pipe. Once your current sink is free, cut through the sealant with a utility knife. You should be able to lift the sink out of place. 

The idea is to get the sink disconnected from any sealant and metal clips that were holding it in place.

With your countertop prepped and correctly measured out, here is how to install an undermount sink. Note that this is a two-person job as lining up the sink will require working from the top and bottom.

How To Install An Undermount Kitchen Sink

What You’ll Need

• Razor scraper
• Caulk gun and Silicone sealant
• Denatured alcohol
• Utility knife
• Wood plank and wood block
• Kitchen towels
• Bar clamps
• Mounting brackets

Steps to Install An Undermount Kitchen Sink

• Prep The Countertop

Prep the countertop so it’s ready to take in an undermount sink. Even out the surface from residual sealant by running a razor scraper over it. 

Once the countertop is smooth, clean and sanitize it. You can run over a microfiber cloth with some all-purpose cleaner and follow it up with a wipedown with denatured alcohol. 

• Add Silicone To The Edges Of The Sink

With the help of another person, line up your undermount sink in the cabinet and below sink hole cut out. When correctly aligned, lower the sink. Using a caulk gun, line the edges with silicone sealant. Lift from the bottom and raise from the top to put the sink into place. 

• Secure The Sink

As the silicone sealant sets, secure the sink using wood planks and a bar clamp across and below your sink. 

First, place a plank across the length of the sink. Place towels where the wood plank rests on the countertop so you don’t scratch it. 

Next, run one end of a bar clamp down the sink hole. Where the bar clamp would rest on the sink, place a wooden block in between. This will protect your sink from getting scratched. 

Lastly, tighten the bar clamp. This setup should secure the sink into place as the sealant sets and while you add the brackets. 

• Install The Brackets

Further secure your undermount sink into place with the mounting brackets it came with. 

• Wipe Off Excess Silicone And Let It Dry

After you’ve secured and tightened your undermount sink into place, wipe away any silicone sealant that seeped out of the edges. When the edges of your sink are clean, allow the sealant to set for at least a day. 

• Install The Fixtures And Plumbing

Once your sink is fully secured, remove the bar clamp and wood planks. You are now ready to attach your faucet and connect your undermount sink to the plumbing. 

Benefits Of An Undermount Sink

An undermount sink pairs well with a kitchen going for a modern look. The hidden rim gives clean and continuous lines to a countertop. Because the rim is below the countertop, cleanup is quick and easy. All you need to do is to wipe countertop mess directly into your sink. Unlike a drop in sink where the lip is elevated, an undermount sink lip doesn’t create a barrier during clean up. 

Undermount Sink Costs

The average cost for an undermount sink is $200 to $500. The price varies mainly on the material and size. For instance a single-basin stainless steel undermount sink will cost less than a double basin copper undermount sink.

Seeing as undermount sinks are less direct to install than a drop in sink, hiring a contractor is usually required. From mounting the sink, securing it and creating a waterproof seal, most contractors charge $230 on average. You can expect to pay $500 for installing large undermount sinks. 

When planning how to install an undermount kitchen sink, the most important place to start is having your sink measured out correctly with your countertop and your outlets. As long as the sink fits from width, depth and length and you have someone to help you during the installation process, a DIY job is very doable.