How to Mount a Sink Under a Quartz Countertop

Mounting a sink under a quartz countertop can seem daunting, but with the right tools and techniques, it can be a straightforward DIY project. Quartz is an engineered stone that is very durable and attractive, making it a popular choice for kitchen countertops today. With proper planning and care, you can have a beautiful, functional sink that will last for years to come.

Measuring and Preparing the Countertop

The first step is to carefully measure and cut out the hole where your sink will be mounted.

  • Measure the size of the sink you have purchased and mark the hole location on the underside of the quartz countertop. Make sure to account for any aprons or edges.
  • Use a straight edge and pencil to draw cutting lines. Make sure to draw the lines slightly smaller than the sink outline. It is better to take your time and cut multiple times for an exact fit.
  • Cut the hole using a diamond-grit hole saw made for quartz. Go slowly and use light pressure. Cool the saw blade periodically with water to avoid cracking the quartz.
  • Check the fit of the sink and use a file or sandpaper to adjust the hole if needed. Test fit again until you have a snug fit.
  • Clean the cut edges of the countertop with denatured alcohol or acetone. This helps the silicone adhesive stick properly when you mount the sink.

Preparing and Mounting the Sink

With the hole cut, now you can move on to installing the sink itself:

  • Set the sink in place on the underside of the countertop to check the fit one last time. Make any minor adjustments needed with sandpaper.
  • Apply silicone caulk around the top edge of the sink where it will contact the quartz. Use a smooth, generous bead for a watertight seal.
  • Carefully lift and position the sink, pressing it into place within the hole. The silicone will hold it in place temporarily.
  • From under the countertop, install the metal brackets, clamps, or clips that came with your sink. Tighten them securely according to the manufacturer’s directions.
  • Apply a second bead of caulk around the seam between the sink and quartz countertop from underneath. Smooth with a moistened finger for a finished look.
  • Allow the silicone to fully cure for at least 24 hours before using the sink. The bond will get stronger over the first 3 days.

Achieving a Seamless Finish

To make your undermount sink virtually invisible:

  • If there are any gaps between the sink and quartz, apply more caulk to fill them in smoothly. Let cure fully.
  • Use the matching quartz cleaner and polish to clean the countertop surface around the sink. This removes caulk residue and brings back the gloss.
  • For a completely seamless look, apply clear silicone caulk around the sink edge on top of the countertop. Carefully smooth and remove any excess.
  • Install the sink drain assembly and hook up the water supply lines according to the manufacturer’s instructions.
  • Turn on the water and check for leaks at all connections. Make any necessary adjustments.
  • Your undermount sink is now securely installed and ready to use!

FAQ About Mounting Sinks Under Quartz

Here are answers to some frequently asked questions about installing an undermount sink with a quartz countertop:

Is mounting a sink under quartz difficult?

While it takes precision and care, it is very doable as a DIY project if you have the right tools and patience. The key is going slowly and testing the fit often.

What tools do I need to mount a sink under quartz?

A diamond grit hole saw, jigsaw, drill, tape measure, silicone caulk and gun, clamps, and sandpaper or files are essential. Safety gear like eye protection is also a must.

Can I mount any sink under quartz?

Most undermount sinks are compatible, but check that yours is designed to be installed below the countertop. Stainless, enamel, fireclay, and composite sinks commonly work with quartz.

Should I get help with the heavy quartz countertop?

Quartz is very heavy, so if possible, having an extra pair of hands to maneuver and support the countertop is wise to prevent cracks or injury.

How long does the silicone take to cure?

It typically takes a full 24 hours to cure initially. Allow 3 days for maximum strength. Don’t use the sink until the silicone has had time to set properly.


Installing an undermount sink into quartz countertops is a manageable project with the right preparation and techniques. Carefully measure and cut the hole, then seal, fasten, and caulk the sink into place securely. Keep the work area clean and give the adhesive time to fully cure before using the finished sink. With some patience and DIY spirit, you can save on installation costs and have a beautiful, durable undermount sink that flawlessly matches your quartz countertop.