How to Install an Undermount Sink to Quartz

There are two ways to install a sink with a quartz countertop. The conventional way is to mount it with its edge sitting on top of the countertop surface. This is referred to as an overmount sink. The alternative is to install a sink below the countertop, known as an undermount sink. 

Here is a step by step guide on how to install the undermount sink with quartz countertops, and the advantages of choosing this installation method.  

Getting started 

Looking for the safest and easiest solution on how to install an undermount sink to a quartz countertop? Installation will be easiest with an unmounted countertop but we have instructions for a countertop that has already been glued down as well. 

Installation on an unmounted countertop  

You’ll need the following tools and supplies:  

• Denatured alcohol.  
• Clear silicone caulk.  
• Clear epoxy resin. 
• Sink suitable for under-the-counter installation – check if your existing sink is suitable for both types of installations.  
• Undermount sink brackets – we recommend “epoxy sink clips” sold in 10-packs (avoid drill types: It’s best to avoid unnecessary drilling into quartz). 

Step 1: Turn the quartz countertop upside down and place it on a flat surface. The sink will be installed on the unfinished underside and then placed directly on top of the cabinets. 

Step 2:  Position the undermount sink on top of the sink hole and ensure that it’s correctly aligned. Using a pencil, trace its outline and remove it.  

Step 3: Use denatured alcohol to clean the edge around the sink hole where the sink will be positioned. The solvent removes any grime to ensure proper bonding with the glue.  

Step 4: You may have up to 10 undermount sink clips in the pack. You can use between 4 to 6. As a recommendation, place one clip at the four outer edges and two clips at the center.  

The clip will have three parts: anchoring post, wingnut, and bracket. Disassemble the clips so you’re left with the anchoring posts.  

Ensure that the anchoring post is at the boundary line on the corners. Using your pencil, trace each clip outline.  

Step 5: Use denatured alcohol to clean the site of the clip installation. Next, mix the epoxy in equal parts and apply it to the clip locations.  

To install the clips in place, firmly press the clip base onto the epoxy until it squeezes through the holes. 

Step 6: The epoxy will need to cure. Don’t immediately install the sink by attaching the bracket or wingnut.  

Step 7: The next step is to apply the silicone caulk on the rim where the sink will sit. You only need one strip. Ensure that it’s a uniform amount all around.  

Step 8: Using the denatured alcohol, clean the rim of the sink before mounting.  Turn it upside down and install it on the boundaries that you’ve marked.  

Press the sink firmly to ensure the proper spreading of the silicone. The weight of the sink should push against the countertop, but if it’s very light, consider using a weight to press it down.  

Step 9: By now the epoxy should have dried and the anchoring posts should be firm to the touch. If so, install the wingnuts and the brackets to secure the sink. 

Step 10: Allow one or two hours for further drying. Finally, install the entire quartz slab on top of the cabinet.

Replacing an undermount sink and when you can’t detach the countertop 

If the quartz countertop is already mounted or glued onto the cabinets, there’s no need to remove it. It is easy to replace an existing sink. Here are both steps:  

Tools and supplies 

• Denatured alcohol  
• Clear silicone caulk  
• Epoxy resin 

• Undermount sink  
• Mounting brackets – for new installations. For replacements, you may use existing brackets  
• Bar clamp  
• A 2 x 4 or 2 x 2 piece of wood that spans the length of the sink hole  
• Utility knife 

When you can’t detach the countertop, just follow steps 2 to 7 as detailed above. After completing these steps, you should have: 

• Attached the mounting bases with epoxy 
• Traced the edge of the sink 
• Cleaned all surfaces where you’ll apply epoxy with denatured alcohol  

To hold and suspend the sink before drying off silicone, you will need to use the bar clamp. First, apply the silicone onto the quartz countertop. Use the bar clamp to suspend the sink in place and wipe off any excess silicone.  

Attach the mounting bracket and wingnuts to secure the sink onto the countertop. Wait for up to 24 hours before removing the clamp.  

For replacement of existing undermount sinks:  

Step 1: Remove the old sink. You can use a knife to cut around the old silicone. Remove the sink from the countertop by unscrewing the undermount brackets. 

Step 2: Dampen a cloth with denatured alcohol and use it to remove any residue for a clean surface.  

Step 3: Apply fresh silicone on the edge of the sink hole.  

Step 4: Install the undermount sink in place. You need to use the bar clamp to hold and tighten it in place. You can wipe off any excess silicone both inside and outside with a cloth.  

Step 5: Reattach the undermount brackets and screw the wingnuts until you have a tight connection.  

Step 6: Wait for up to 24 hours for adequate drying of the silicone. Proceed to install other fittings.  

How to install undermount bathroom sink to quartz 

It’s essentially the same process as installing an undermount kitchen sink. The only variation is that the sink may be smaller and thicker. Undermount sink clips are often manufactured to adjust to different thicknesses. Fasten them until they grip the sink’s edge adequately. Silicone caulk will bind a ceramic sink to a quartz countertop base with no issues.  

Why choose an undermount sink with a quartz countertop  

Homeowners favor undermount sinks for the high-end look. They promote better drainage by preventing the accumulation of water on top of the countertops.  

Top-mounted sinks take up valuable counter space that’s freed by an undermount sink. Because they are often deeper, they provide more sound dampening. It’s the ideal choice if you’re considering a more modern look that enhances clean and straight lines with a minimalistic appeal.