How to Install an Undermount Sink with Quartz Countertop

Installing an undermount sink with a quartz countertop can seem daunting, but with proper planning and the right techniques, it can be a smooth process. Here is a comprehensive guide on how to install an undermount sink with a quartz countertop.

Things to Consider Before Installation

Before starting the installation, here are some key things to keep in mind:

  • Choose the right undermount sink and faucet – Make sure to pick an undermount sink and faucet that will complement your quartz countertop. Consider size, materials, style and performance.
  • Have all necessary supplies – You will need silicone/adhesive caulk, brackets, screws, tape, tools for cutting the countertop, etc. Have everything readily available.
  • Take accurate measurements – Precisely measure the sink dimensions, placement on the countertop, and faucet hole locations. Plan accordingly.
  • Account for support and reinforcement – Undermount sinks require solid support. Determine if you need to add support framing or blocks under the sink.
  • Prepare the countertop – Make sure the quartz countertop is cleaned and ready for installation. Remove any debris or dust.

Step-by-Step Installation Process

Follow these key steps to properly install the undermount sink:

Cut the Sink Hole in the Quartz Countertop

  • Outline the sink perimeter on the bottom of the quartz countertop using a marker.
  • Using a straight edge, scribe cutting lines about 1/8 inch inside the sink outline.
  • Cut along the inside of the scribed line using a specialty quartz cutting tool. Make rounded corners to help the sink fit.
  • Check regularly that the sink fits the hole cleanly. Trim if needed for a perfect fit.

Mount and Secure the Undermount Sink

  • Clean the bottom of the sink and mating countertop surface with alcohol.
  • Apply a thick bead of silicone adhesive caulk around the top edge of the sink.
  • Position and align the sink centered to the hole in the countertop. Press firmly.
  • From under the sink, install the mounting brackets loosely to hold up the sink temporarily.
  • Check alignment and make any adjustments needed. Tighten the mounting brackets evenly.
  • Add screw clamps if needed for extra support, especially for heavy sinks.

Install the Faucet and Make Plumbing Connections

  • Drill precise holes for the faucet based on manufacturer specs, if needed.
  • Place a bead of caulk around the edges of the faucet holes.
  • From above, install the faucet and fasten it per instructions.
  • From under the sink, connect water supply lines and p-trap drain. Make sure to seal connections.

Finish With Silicone Caulk and Clean Up

  • Allow the caulk to set and cure according to manufacturer’s guidelines.
  • Apply a smooth, continuous bead of silicone caulk around the entire sink and countertop seam.
  • Use caulk smoothing tools to blend for a seamless look. Remove any excess caulk.
  • Let the caulk fully cure for 24-48 hours before use. Avoid wetting the area.
  • Clean up any debris and tools. The undermount sink quartz countertop installation is complete!

FAQs About Installing Undermount Sinks with Quartz Countertops

What kind of support does an undermount sink need?

Undermount sinks should be solidly supported below. You can use 2×4 bracing, extra plywood, or buy a special metal sink support frame. Proper support prevents sinking or separation.

What is the best adhesive to attach an undermount sink?
Use a flexible, waterproof silicone or polyurethane adhesive caulk to attach an undermount sink. These adhesives move with the slight expansion/contraction of materials.

How do you cut a hole in quartz for an undermount sink?
Use a specialty quartz cutting tool, such as a quartz wet saw. Follow the manufactures’s safety and usage guidelines. Make rounded corners.

Can I install an undermount sink myself?
With proper planning and tools, an experienced DIYer can self-install an undermount sink. Professional installation may be better for complex jobs or expensive countertops.

What thickness should the quartz countertop be for an undermount sink?
The manufacturer’s guidelines should be followed. In general, 3/4″ to 1-1/4″ thickness is recommended for undermount quartz countertops with sinks. Go thicker for heavily used sinks.

Should I caulk under the sink edge?
Yes, caulking around the sink edges helps prevent leaks and damage. Use a thin bead of silicone caulk before setting the sink and a finishing bead after install for a watertight seal.


Installing an undermount sink into a beautiful quartz countertop can give your kitchen an upscale, seamless look. With attention to detail in the planning and preparation stages, accurate cutting, secure support, bead adhesion, and smooth caulking, the process can go smoothly resulting in a sturdy, high-end installation that will last for many years. Take precautions, follow sink and countertop manufacturers’ recommendations, and don’t be afraid to call in a pro if the project seems too complex. With some patience and the right techniques, you can have a stunning new undermount sink and quartz countertop that the whole family can enjoy.