undermount sinks pair beautifully with granite countertops, creating a seamless and modern look. However, because granite is heavy and non-porous, the sink must be installed securely to avoid leaks or sagging over time. Here’s a detailed guide on how to properly install an undermount sink to granite.

Tools and Materials You’ll Need

• Undermount sink (stainless steel, composite, or ceramic)

• Mounting clips or sink support brackets

• High-strength silicone sealant (kitchen/bath grade)

• Epoxy adhesive (optional for extra bonding)

• Clamps, wooden braces, or sink support system

• Drill with diamond or carbide bits (if anchor holes are required)

• Rubbing alcohol and cloth (to clean surfaces)

• Plumber’s putty (for drain installation)

Step 1: Prepare the Granite Countertop

1. Ensure the sink cutout in the granite matches the sink dimensions.

2. Smooth and polish the inside edges of the granite to prevent chipping.

3. Test-fit the sink to confirm proper alignment.

Step 2: Clean the Contact Surfaces

1. Wipe the underside of the granite around the cutout with rubbing alcohol to remove dust and oils.

2. Clean the rim of the sink as well. This ensures strong adhesion.

Step 3: Apply Silicone Sealant

1. Run a continuous bead of waterproof silicone around the sink flange.

2. Position the sink against the underside of the granite cutout.

Step 4: Secure the Sink

1. Use clamps, sink clips, or a support frame to hold the sink tightly against the granite.

2. If using mounting clips, drill shallow anchor holes into the granite underside with a diamond or carbide drill bit (be extremely careful to avoid cracking).

3. Tighten the clips or brackets evenly around the sink perimeter.

4. Wipe away any excess sealant that squeezes out.

Step 5: Allow Sealant to Cure

• Let the silicone cure for 12–24 hours before connecting plumbing or using the sink.

• Do not remove supports until the sealant has fully hardened.

Step 6: Install Drain and Plumbing

1. Apply plumber’s putty to the drain flange and install the drain assembly.

2. Reconnect the plumbing, garbage disposal, or water filter tap as needed.

3. Test for leaks by running water and checking all joints.

Real-World Example

A homeowner in California installed a 16-gauge stainless steel undermount sink beneath a granite countertop. By using eight stainless steel mounting clips and heavy-duty silicone, the sink was secured overnight. After five years of daily use with heavy pots and pans, the installation remains sturdy and leak-free.

Tips for Success

• Always use support brackets for larger or heavier sinks.

• Work slowly when drilling granite to avoid cracks.

• Choose 16 or 18 gauge stainless steel sinks for better durability.

• Never skip curing time—the sealant must fully harden to prevent sagging or leaks.

Conclusion

Installing an undermount sink to granite requires precise alignment, strong adhesives, and secure support systems. With the right tools and careful preparation, you can achieve a professional, seamless installation that combines the durability of granite with the sleek look of an undermount sink.